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Thermally Comfortable Affordable Housing: A study on Residential Building Code in India (2021)

Sneha Asranil, Rajan Rawal, Yash Shukla, Peter Graham, Priyanka Bhanushali, Arjun Desai
Abstract: On an average, India has more than 3000 Cooling Degree Days (CDD). The multifamily public housing being constructed under India’s Prime Minister Awas Yojana (PMAY) is aimed at providing formal housing to the society’s Economic Weaker Section (EWS). It is essential that this housing delivers thermally comfortable indoors to the occupants. This study mapped the design and construction practices followed under PMAY Urban (PMAY-U) against India’s Residential Energy Building Code, Eco Niwas Samhita (ENS). The metric prescribed in ENS is Residential Envelope Transmittance Value (RETV). For 80 PMAY-U projects, information related to spatial design, and walling assemblies was collated. 30 projects were short-listed for detailed analysis. The RETV for selected projects was calculated. The analysis demonstrated that walling assemblies and technologies having a lower thermal transmittance value (U-value) resulted in meeting the ENS prescribed RETV numbers, hence, code compliance. The study further extended to assess the energy performance of the housing unit by exploring the change in walling assemblies. The change in thermally comfortable hours were reported in the range of 4145 and 6034, and Energy Performance Index (EPI) of the dwelling units were reported between 64 and 68 kWh/m2/year for the various walling assemblies.

Keywords: PMAY, Residential Building Code, Eco Niwas Samhita, Adaptive Thermal Comfort

Presented at: Comfort At The Extremes, CATE’21, Muscat, Sultanate of Oman, October 2021

Urban Form and Energy Consumption in Wastewater Management: Case Study of Ahmedabad (2021)

Srushti Thakur, Mona Iyer, Palak Patel, Sachin. S, Rajan Rawal
Abstract: Municipal services account for 4% of the total electricity consumption in India. In wastewater management value chain, 40% - 80% of the operational expenditure is on electricity. Conventionally, energy efficiency studies and interventions focus on electro-mechanical aspects of pumping assets.This research assesses and establishes empirical relationships between urban form parameters like built-up area, pumping station command area, ground coverage, topography etc with energy consumption at sewage pumping stations in Ahmedabad city. This shall inform city planners in planning energy efficient wastewater systems while preparing spatial plans and simulating energy consumption for new areas based on urban form. Efficient energy consumption would result in cost saving. Research gives indications towards horizontal versus vertical expansion of cities to move towards sustainable development goals like clean water and sanitation, affordable and clean energy and climate action. This would certainly require inputs on other aspects of city planning like land costs, transportation networks.

Key Words: Wastewater management; Energy efficiency; Energy consumption; Urban form;Urban planning;Sustainable cities

Presented at: ICWSS21: International eConference on Water Source Sustainability Roorkee, India, June 18-20, 2021

Urban Planning and Energy Consumption in Storm Water Management: Case Study of Ahmedabad (2021)

Sakshi Sharma, Mona Iyer, Palak Patel, Sachin. S, Rajan Rawal
Abstract: Rapid urbanization has resulted in fast development and stress on the water cycle and energy consumption. Increased built and paved surfaces lead to increased surface runoff and urban flooding. This also increases the inflow in conduit-based, electromechanical stormwater systems of a city, resulting in more energy consumption. This research establishes an empirical relation between energy consumption in stormwater management and urban characteristics like vegetation, surface pattern, built-up area, etc. for the city of Ahmedabad. Urban planning with due consideration to these factors could facilitate decisions on the proportion of conduit-based systems and optimize the presence of blue-green infrastructure, surface pattern, and other urban factors like built vs open, land use, etc. Also, these factors would help achieve sustainable development goals in the long term like SDG 6: Clean water and sanitation, SDG 11: Sustainable cities and communities, SDG 13: Climate Action, and SDG 15: Life on land.

Key Words:Energy Consumption; Municipal Service; Stormwater management; Urban Planning;Energy Efficient; Urban factors

Presented at: ICWSS21: International eConference on Water Source Sustainability Roorkee, India, June 18-20, 2021

City Level Fuel Energy Efficiency in Municipal Solid Waste Collection: A Case of Ahmedabad (2020)

Sneha Bhattacharyya, Mona Iyer, Sachin.S, Rajan Rawal
Abstract: Efficient service delivery in the Municipal Solid Waste Management sector by default implies regular waste removal from the habitation to a treat-ment or disposal facility. In the 21st century, such service delivery in large cit-ies demands on the deployment of motorised vehicles for the transport of waste. However, the ULBs in India remain oblivious to the fuel consumption among the fleet deployed. This study consists of two parts addressing the fuel efficien-cy of MSW management in Ahmedabad. The first part of the study explores the significance of fuel consumption in the energy footprint of municipal solid waste collection through the preparation of an inventory for capturing the fuel consumption data. The second part of the study identifies fuel consumption as an evaluation criterion for energy audits within the waste collection and trans-portation system. The study has been executed in 4 stages involving review of relevant literature, consultations with the Ahmedabad Municipal Corporation, data compilation, and city and ward level analysis. Both quantitative and quali-tative analyses have been carried out using mapping and statistical tools. The study has revealed the impacts of various urban parameters on the fuel con-sumption in MSW collection. Waste collection vehicles in Ahmedabad are de-ployed such that 100% waste collection can be ensured resulting in the over uti-lisation of 1-ton capacity vehicles owing to their suitability. Service delivery parameters such as driving speed and efficient time management during the loading of waste at the point of services also influence fuel consumption in the collection process.

Keywords: Fuel Consumption; Fuel Efficiency; Municipal Solid Waste Man-agement; Urban Form; City Level Assessment

Building Level Energy Consumption in Water Services for the City of Ahmedabad (2020)

Palak Patel, Mona Iyer, Sachin.S, Rajan Rawal
Abstract: The initiatives taken for energy efficiency in India have largely focused on street lighting, water pumping for irrigation, energy-intensive industries, and the building sector. Studies on the building sector have explored the relationship between built form and energy consumption in terms of solar energy, heat energy demand, and passive cooling. However, there is limited empirical research on municipal ser-vices like water pumping at the building level. This study aims at inves-tigating the energy efficiency in water services at the building level, through establishing the relationship between urban morphology and electricity consumption for pumping the water in Ahmedabad city. Fo-cusing on the aspect of urban resilient planning, various factors of ur-ban morphology were explored such as building height, total popula-tion, floor space area, age of the building. To establish the relationship, the electricity consumed to pump water from the ground to the terrace level was measured for residential building typologies of low rise, mid-rise and high rise. The results obtained from the study show that there is a significant impact of building height on the per capita energy con-sumption for pumping water. This suggests that the high-rise buildings are more energy-intensive compared to low-rise and mid-rise typolo-gies. The total population is higher in low-rise and high-rise compared to mid-rise typology, hence the relationship acquired between total population and per capita electricity use is stronger for mid-rise build-ings. The age of the building and floor space area have an insignificant influence on the electricity used to pump water.

Keywords: Water pumping; Electricity consumption; Urban morphol-ogy; Residential building typologies; Building level

City Specific Dynamics of Energy, Environment and Comfort for Room Air Conditioner Performance (2020)

Nidhi Rai Jain, Rajan Rawal
Abstract: Final energy use for cooling in buildings has tripled between 1990 and 2016 to 2020 terawatt hours. Excluding China and Japan, India accounts for about 28% of the Room Air Conditioner (RAC) market in Asia. RAC penetration is comparatively lower at 5% in India but raising with 12% CAGR growth. Use of RAC provides thermal comfort leading to better living standard, simultaneously use of energy and refrigerant to operate RAC impact environment. Seasonal Energy Efficiency Ratio (SEER) is the most used method to quantify the energy efficiency of RAC. The importance of comprehensive environment impact, accounting direct and indirect emissions by RAC will help mitigate environmental challenges. This paper adopts a methodology using ISO 16358-1 combined with hourly temperature bin to calculate Indian SEER (ISEER). Cooling Seasonal Energy Consumption (CSEC) is developed as a metric accounting different climate represented by cities and comfort models. Total Equivalent Warming Impact (TEWI) was used to account direct (refrigerants) and indirect (energy consumption) emissions. The study accounts for 12 Indian cities having high GDP growth, four RAC selected out of 282 RAC surveyed for the study. In comparison of ISEER mentioned by BEE, the study observes 9-20% higher ISEER in New Delhi and 9-16% lower in Bangalore. CSEC and TEWI are observed to be highest in Ahmedabad and lowest in Bangalore with a maximum difference of 2,520 kWh/year and 20,640 CO2-eq respectively. For Delhi, CSEC was observed at 23% lower with adaptive comfort model for AC operation building then static comfort model. The contribution of direct emissions to TEWI was observed 10-20% with R410a and 4-8% with R32.

Presented at: ENERGISE INDIA 2020, At Hyderabad

Three Sides of Coin: Connecting Cooling Capacity, Environmental Impact and Comfort (2019)

Nidhi Rai Jain, Rajan Rawal
Abstract: In India, the energy end-use is anticipated to increase by 56% from 2014 to 2050. It shares 12% of total carbon emissions in the world by Room Air Conditioners (RACs). As increase in energy production using fossil fuels has an adverse effect on climate, there is an immediate need to focus on mitigation scenario. It counts on the change of refrigerant, improvements in system design efficiency and operational approach. Growth in urbanization and rising income is persuading the use of mechanical cooling for better comfort. Seasonal Energy Efficiency Ratio (SEER) is the most used method to quantify efficiency of RAC. Environmental impact of the system is still unexplored. This paper summarizes a methodology proposed to determine the effect of energy performance and indoor comfort temperature in total environmental impact by a RAC. The study was conducted in four stages. Initially, relevant metrics were identified from past work to quantify the parameters. 12 Indian cities were selected based on GDP growth for analysis. Four RAC units were selected based on findings from market survey of 282 RAC systems available in the country. In the third stage, ISEER and annual energy consumption were calculated for 12 cities using ISO 16358-1 and temperature bin hour calculations. Carbon emissions were calculated using Total Equivalent Warming Impact (TEWI) score which comprises of direct (refrigerants) and indirect (energy consumption) emissions. Further, annual discomfort degree hours were calculated to quantify the cooling demand for static and adaptive indoor set-point temperatures. Lastly, the results obtained show that the dependence of carbon emissions is more on annual cooling hours (comfort) than the system seasonal energy performance. Above 40°C, for peak load conditions only 5 cities experience more than 20 hours annually. Savings of more than 60% in total environmental impact can be achieved by incorporating adaptive indoor set-point temperatures. Presented at: 7th International Conference on Energy Research and Development 2019, At Kuwait

A Simplified Method for Estimating Cooling Energy Savings Due to Passive Strategies for Indian Cities (2019)

Arjun Desai, Prasad Vaidya, Sanchi Pathela
Abstract: Different methods are used for calculating the energy consumption of buildings. While the heat balance method, weighing factor method and thermal network methods are complex and require intense computing power, the degree-day and the BIN methods are relatively simple. In this study, we have used the degree-day approach published in CIBSE TM-41 to develop a Python tool to calculate the energy consumption of energy buildings on an hourly basis. The tool calculates the building energy for 59 Indian cities for five different cases: 1) fully air-conditioned, 2) with evaporative pre cooling, 3) evaporative cooling, 4) with comfort cooling and 5) with night ventilation with five different thermal comfort models. These cases are run for two building versions: 1) Business as Usual and 2) Energy Conservation Building Code compliant , and the study resulted in two realistic versions of Balance Point Temperatures for these cases. In total these add up to 2900 simulation which the Python tool completes within 1 hour. The results are shown in an excel dashboard.

The results indicate the cooling energy reduction possible due to the three passive design strategies. The CDD-based results are compared with EnergyPlus results. The Normalised Mean Biased Error is 4.6% while the Root Mean Squared Error value is 15%.

Presented at: Building Simulation conference held at Rome – Sep 2019

Impact of Building Energy Code at City Level Energy Consumption – A Study in the Context of Ahmedabad, India (2019)

Rajan Rawal, Kartikay Sharma, Himani Pandya
Abstract: This paper demonstrates the impact of Energy Conservation Building Code (ECBC), India implementation in the city of Ahmedabad India. The study uses available administrative and property tax data from the local government in conjunction with building energy simulation to estimate the benefits of various energy conservation measures (ECM) proposed in the ECBC. The study compares ECM between two versions of the code titled ECBC 2007 and ECBC 2017. It also investigates the impact of three stringencies defined in ECBC 2017. The paper establishes the energy saving impact due to only envelop measures, due to Envelope & HVAC measures combined and due to the deployment of all ECM mandated in the ECBC. To envisage the impact of ECM at the city level the paper estimates growth in floor space up to the year 2047 and then attempts to envisage energy saving potential. Selection of 2047 is based on its significance since India will celebrate the 100th year of its independence. The paper also attempts to estimate future saving potential in event of code implementation. The paper correlates the amount of floor space of various types of buildings in the city with total energy saving potential due to the partial deployment of code only for certain types of buildings. It also estimates savings due to partial compliance of code for certain building types based on ease of implementation i.e. it estimates 6% savings if all large office buildings in the city meet only envelop requirement of ECBC 2017 but 27% savings in the event of enforcement of all ECM of ECBC 2017. The paper helps to understand the impact of various building types and impact of various ECM at the building level and at the city level. The paper provides valuable guidance to policymakers for code implementation and enforcement of code based on various stringencies and/or based on the implementation and enforcement scope of the code.

Presented at: Building Simulation conference held at Rome – Sep 2019

Strategic framework for Net Zero Energy Campus in India: A case of CEPT University Campus (2016)

Amiya Behera, Yash Shukla, Rajan Rawal
Absract: To achieve indoor environmental comfort conditions and to facilitate economic activities, building occupants use electric energy. In conventional scenario electric grid provides electricity to buildings. This study attempts to evaluate feasibility of CEPT University campus – an academic, research and development facility located in hot and dry climate zone in India, to become net zero energy campus. A pilot case has been taken as a preliminary study of the research work. Study starts with detailed monitoring of indoor environmental comfort parameters such as temperature, humidity, energy used for various functions such as HVAC, lighting and plug loads, of a newly established net zero energy building located at Anand, Gujrat. While studying this, concurrent energy generation from roof top solar PV was also studied. In second stage campus was divided into number of electrical zones and individual or group of buildings according to electrical loads and locations, were monitored for its energy use. This exercise provides energy consumption profile. CEPT University campus being an academic, research and development, it has varied operation schedule across the year. Campus also hosts indoor spaces with high diversity of use, such as design studios, seminar rooms, library, administration, workshops and ancillary activities. Hence it is important to conduct year round monitoring to capture yearly electricity usage profile, Solar roof top PV generation and indoor environmental conditions. Synthesis of collected data was analysed. Considering availability of areas for solar roof top PV installation, final observations were made to suggest feasibility of net zero energy campus of CEPT university. Study was taken further to develop framework of renewable energy generation installations, economic analysis and technical potential.

Presented at: 15th International Conference on Sustainable Energy Technologies (SET 2016)

Residential buildings in India: Energy use projections and savings potentials (2015)

Yash Shukla, Rajan Rawal, Sophie Shnapp
Abstract: As energy consumption from residential buildings is predicted to rise by more than eight times by 2050, it is of vital importance for India to develop energy-efficiency strategies focused on the residential sector to limit the current trend of unsustainable escalating energy demand. This study investigates impeded growth in energy consumption in the Indian residential sector and documents energy saving potentials that can be achieved with the focused policy and market efforts. The study specifically focuses on assessing the role of building envelopes in relation to comfort air conditioning systems and appliances in order to ensure energy efficient dwellings for urban and rural residential sectors.

The study conducted a survey of 800 households, in four-climate zones of India, to map current equipment penetration rate and electricity consumption patterns. Key information including residential unit area, monthly energy consumption, connected load, number of appliances & their power rating, as well as operational patterns, has been gathered in a survey. Building energy modeling (using EnergyPlus) was then deployed to quantify comfort benefits and energy savings potentials of better performing building envelopes.

The trends observed during survey and building energy modeling analysis, along with the information from past studies, have been used to derive residential electric energy projections till 2050. The projections in the study have been segregated by three end use segments (air conditioning, envelope, and equipment) for urban and rural residential sectors. Projection scenarios show that the electricity consumption will rise by more than eight times under the business-as-usual scenario. With the focused policy and market efforts, the electricity rise in residential sectors can be restricted to five times, four times, and three times that of current energy use under modest, aggressive, and very aggressive scenarios.

Presented at: ECEEE 2015 Summer Study on energy efficiency
Conference proceedings are available on
: http://proceedings.eceee.org/visabstrakt.php?event=5&doc=6-020-15

Approach to Building Energy Codes implementation in India (2015)

Rajan Rawal, Prasad Vaidya, Sanyogita Manu
Abstract: Various works carried out by Centre for Advanced Research in Building Science and Energy (CARBSE) at CEPT University, Ahmedabad, has been discussed in this paper. The objective of this project was also to develop a framework for Third Party Assessor (TPA) model to facilitate ECBC compliance and enforcement. The proposed Third Party Assessor framework can resolve the issues of capacity and expertise to enforce ECBC at the local government level. However, coordinating with different government agencies and other relevant stakeholders to incorporate the TPA framework would be a challenging and time-consuming initiative. A tiered approach to ECBC compliance has been proposed wherein, Tier 1 includes those requirements of ECBC that are easy for market adoption, have a high energy savings potential, and are enforceable through the current building permit process, while tiers 2 and 3 include additional measures of ECBC that are more difficult to implement or enforce, given the current practices, and have a lower potential for energy conservation.

Presented at: International Conference on Energy Efficiency in Buildings (ICEEB), December 17-18, New Delhi, 2015.
Conference proceedings are available on: http://www.undp.org/content/dam/india/docs/ICEEB%202015_Compendium.pdf

ECOnirman & third party assessors: innovative approaches to energy code compliance and enforcement in India (2013)

Rajan Rawal, Vinay Ghatti, Sanyogita Manu, Smita Chandiwala, Prasad Vaidya
Abstract: Compliance with Energy Conservation Building Code (ECBC) of India can save up to 1.7 billion kWh annually. ECBC enforcement poses significant challenges to local governments who are responsible for enforcement given India’s 12th Five Year Plan’s compliance goals. This paper summarizes two important initiatives taken up in India for making implementation and enforcement easier, leap-frogging the challenges that have been experienced in other countries.

In the first initiative, the United States Agency for International Development supported the development of the ECOnirman Whole Building Performance Tool, an online code compliance energy simulation tool. It assists developers and building designers in demonstrating performance-based compliance. It shows great promise for the future in India: it enables building developers to meet code by installing only those measures that improve their building's energy performance; it promotes innovation in design and technologies; it enables a large user-base to do energy simulations and results in true capacity building; and the database of inputs and results enables policy analysis. Tying the metered energy use of the buildings to the ECOnirman database will result in a robust dataset that will be a powerful policy tool for future programs, rating and labelling of buildings.

The other code compliance initiative is a nationwide Third Party Assessor (TPA) framework for compliance checking of ECBC. Urban Local Bodies (ULB) that enforce building and development rules and bye-laws, face technical and manpower related challenges when enforcing ECBC. This paper discusses the background research, the stakeholder engagement, and the institutional framework proposed for allowing a TPA model to be used across India.

This paper provides recommendations and next steps for ECBC compliance through future development of ECOnirman and implementation of the TPA framework.

Presented at: eceee 2013 Summer Study, France.
Conference proceedings are available on: http://proceedings.eceee.org/visabstrakt.php?event=3&doc=5A-518-13

BS2013 – Deployment of energy simulation for design of voluntary window labeling program in India (2013)

Rajan Rawal, Srijan Didwania, Yash Shukla, Sanyogita Manu, Purvi Panchal
Abstract: India has experienced an average economic growth of 10% since 1991 leading to the establishment of new commercial buildings. Amongst other initiatives, Indian government enacted the Energy Conservation Act in 2001 (EC Act 2001), predominantly for commercial buildings. Government of India is relying on mandatory building energy code and voluntary standards and labeling (S&L) program to foster energy efficiency in commercial buildings. Learning from S&L home appliances program the government has initiated the formation of building component labelling programs for windows, walls and roof. This paper is part of a research that aims to map the state of current affairs in Indian fenestration industry and fenestration labelling programs from across the world. The research involves evaluation of thermal and optical performance of windows available in Indian market and compares them against those prescribed in the energy code. Further it suggests mechanisms for the formation, implementation and administration of window labelling program in India. This paper also focuses on estimation of energy saving potential of high performance window systems, their payback period by using a combination of window simulation program such as WINDOW-THERM-Optics and whole building energy simulation program such as EnergyPlus.

Presented at: 13th International IBPSA Conference - BS2013, At Chambery, France
Conference proceedings are available on: http://www.ibpsa.org/proceedings/BS2013/p_1469.pdf

Energy Code Enforcement for Beginners: A Tiered Approach to Energy Code in India (2012)

Rajan Rawal, Prasad Vaidya, Vinay Ghatti
Abstract: In the next 18 years, India will add 67% of the floor space projected for 2030, or about 2.3 billion square meters. Buildings consume 33% of total energy in India and this is growing at 8% per annum. For a large scale market change, the Bureau of Energy Efficiency developed the Energy Conservation Building Code (ECBC). Through mandatory ECBC compliance, India can achieve an annual energy saving of 1.7 billion kWh. The rate of compliance with ECBC is forecasted at 10% until 2013, 35% in 2015 and 65% by 2017. To achieve this, ECBC must be adopted by the states and barriers to enforcement by local governments must be overcome.

Shakti Sustainable Energy Foundation funded a study to develop a tiered approach to compliance, with evaluation of individual ECBC measures for energy savings, incremental cost, and ease of enforcement. The findings were peer reviewed and the measures were then bundled in to tiers. Lower tiers include ECBC measures that are easy for market adoption, and are enforceable through the current building permit process. This will help build capacity over time and allow developers to get experience with building energy efficiency. It will help enforce ECBC and build capacity at same time without reducing stringency of the code. This approach can be enforced more effectively given the current construction and real estate practices.

This paper summarizes the analysis and presents the policy case for the Tiered approach.

Presented at: ACEEE Summer Study on Energy Efficiency in Buildings, USA, 2012
Conference proceedings are available on: http://aceee.org/files/proceedings/2012/data/papers/0193-000113.pdf

Thermal performance of vegetation on urban microclimate (2011)

Jalpa Gandhi, Rajan Rawal
Abstract: Urbanization has direct impact on the spatial structure of the city, which in turn results in the dramatic change of the overall immediate environment. High-rise, high density built areas provides multiple surfaces for the reflection of direct and indirect solar radiation as well as absorption & storage of the anthropogenic heat. It is often seen that this heat gets re-radiated & trapped due to neighborhood buildings causing changes in surface & ambient air temperature. To mitigate such effect various approaches were studied and experimented in the past. Out of which impact of vegetation is considered to be one of the most potent measure to mitigate negative impact of urban form on high surface and air temperature. This is proved through number of research studies and on-site measurements. This study is an approach to understand the role of urban environment on urban area micro-climate with reference to vegetation in the city of Gandhinagar, India. An urban area of Central Business District is configured according to the rules of ground coverage, floor space index (FSI) and site setback as mentioned and laid out in building byelaws of city. For the purpose of this study a three dimensional numerical computer model ENVI-met V3.4, that analyzes micro scale thermal interaction with urban environment is used. Input of environmental data is extracted from Ahmedabad IWEC weather file. Simulations are done for typical summer day. Parametric variations are made to get prediction of surface and air temperature in different built and un-built conditions. Different scenarios are designed besides the model condition where studies are done on basis of different surface materials, changing density of vegetation & changing the type of vegetation. The results are evaluated on the basis of ambient air temperature & Surface temperature. Findings show that on an average 2°C drop in ambient air temperature is achieved in urban area of Gandhinagar’s microclimate with the addition of trees. Vegetation is seen more valuable during harsh afternoon hours, due to its shading and evapo-transpiration properties. This suggests that shading streets with trees is advisable, which results in achieving reduction of minimum 0.5°C & maximum 1.5°C average air temperature across the year. The cooling effect of trees is also seen in the surrounding areas. Strategic plantation of trees and selection of surface material is found as very important aspects to lower adverse effect of urbanization.

Presented at: 5th International Conference on Energy Research and Development. Kuwait.2012

An Initial Parametric Evaluation of the Impact of the Energy Conservation Building Code of India on Commercial Building Sector (2011)

Sanyogita Manu, Justin Wong, Rajan Rawal
Abstract: The Energy Conservation Building Code (ECBC) was launched in India in May 2007 under the Energy Conservation Act, 2001. It offers two compliance approaches - Prescriptive and Whole Building Performance (WBP). According to the EC Act, compliance with the ECBC has to be expressed in terms of Energy Performance Index (EPI) which is the annual energy consumption per square meter of floor area, and is only possible via the WPB compliance approach. However, as the Prescriptive compliance approach is relatively easy to implement and enforce, it may be assumed that once ECBC is made mandatory at local level, the Prescriptive approach will be a more widely used compliance path over WBP owing to ease of integration with the existing building regulations. This paper aims to link ECBC Prescriptive requirements to the EPI performance metric in order to bridge the gap that exists between EC Act and ECBC Prescriptive compliance method.

The simulation results help in understanding the relative impact of ECBC Prescriptive requirements and prioritizing the Energy Conservation Measures (ECMs). The results are extrapolated to understand the long-­term impact of the code on national energy savings. The paper also provides an insight into the sensitivity of the various ECMs in different climatic zones.

Presented at: International Building Performance Simulation Association -An IBPSA-AIRAH conference, November 2011, Sydney.
Conference proceedings are available on:

Integration of solar photovoltaics: to suffice interior lighting energy consumption of office buildings in ahmedabad – An approach towards zero lighting energy consumption (2011)

Ashima Charnalia, Jyotirmay Mathur and Rajan Rawal
Abstract: The study focuses on ways to minimize interior lighting energy consumption (ILEC) in daytime use office buildings and proposes use of solar photovoltaic’s (SPVs) to suffice the remaining lighting energy requirement. The objective of the study is to attain interior lighting energy autonomy through Solar Photovoltaic’s. The study in whole focuses on low interior lighting energy consuming building designs whose interior lighting electricity loads are almost entirely met by grid connected roof top SPV systems. Energy Conservation Building Code (ECBC-2007-India) compliant hypothetical building models representative of office buildings in the hot-dry climate of Ahmedabad were modeled in Design Builder on Energy Plus platform. Fifty-four scenarios in all were examined for three-floor plate areas (500, 750 & 1000 m2). The scenarios were derived by keeping the carpet area constant of all the floor plates and varying building aspect ratios, orientation (1:1, 1:2 & 2:1), window wall ratio (40% & 60%) and applying external daylighting devices such as louvers and light shelves. From these scenarios, one building case for all the three different floor plates with the least ILEC was proceeded to integrate rooftop-grid SPV system (24KW SPV system for 500 m2, 36KW SPV system for 750 m2 and 48KW SPV system for 1000 m2 ) to arrive at potential energy generation figures. The study analyzed the two aspects – Energy and Economics, of the attempt. For first Energy analysis, the study analyzed annually to hourly interaction between the building’s ILEC and SPV energy generation. On annual basis, the study was able to illustrate a potential scenario to serve ILEC of 3.8 floors for 500 m2 floor plate, 3.4 floors for 750 m2 floor plate and 3.2 floors for 1000 m2 floor plate of the same building by the same roof top SPV system designed as per floor plate areas. These results were also due to interaction of energy imports and export with the utility grid but the system annually made no net demands on the utility grid to serve ILEC. This meant that ILEC of more than three floors of a building for all three-floor plate areas were demonstrated to be net zero by integration of SPV roof top system.

The results of three floor plates also demonstrated that with every increase of 250 m2 floor plate area, there is a percentage increase of 56.8% in annual ILEC, with percentage increase of 50% in annual roof top energy generation, with percentage increase of 62.5% in annual energy imports from the grid, with percentage increase of 46.5% in annual energy exports to the grid. This implies that with increasing the floor plate area as the core area increases, there is a percentage decrease of 32.8% in annual net surplus energy on site.The second analysis Economics part, the study projected the life period energy summary to obtain life period cost summary of the installed SPV systems, which demonstrated that rooftop SPV system is still very high capital incentive investment with payback period of 22-24 years, without considering any government subsidiaries. Overall, the study demonstrates a sustainable approach towards interior lighting energy use in the building sector by utilizing renewable solar energy source.

Presented at: International Building Performance Simulation Association -An IBPSA-AIRAH conference, November 2011, Sydney.
Conference proceedings are available on: http://www.ibpsa.org/proceedings/BS2011/P_1628.pdf

Potential Savings in lighting energy due to advancement in Indian Standard time: An Enquiry in context OF COMMERCIAL office spaces in India. (2011)

Padmini Rajaram, Rajan Rawal
Abstract: Indian Standard Time (IST) is calculated with reference to 82.5° E longitude and the difference of +0530 hours from Greenwich Mean Time (GMT). The permanent advancement of IST was proposed in the previous study from +0530 to +0600 hours with reference to 90° E longitude and is estimated to 16% of savings in peak load electricity demand by analyzing all the power consuming sectors such as industrial, agricultural and commercial sectors of India(Ahuja.et al,2006). The present study aims at quantifying the savings in lighting energy consumption for office buildings, due to the permanent advancement of Indian standard time from +0530 to +0600 hours (GMT).The study initiates by walk through energy audit to evaluate lighting load details and occupancy details for two cities; Ahmedabad in the west and Kolkata in the east of India, which are 64 minutes distant from each other. The audited data is used as input parameters for reference models that are modeled using design builder with energy plus platform to determine annual energy consumption for lighting in office buildings. The time advancement in this study is analyzed by evaluating shift in occupancy schedules for offices. Hence parametric combinations of occupancy schedules of 1000 -1900 hours versus 0930-1830 hrs, and 0930-1830 versus 0900-1800 hrs are examined for varying floor plate sizes of 100m², 400m², 800m² and 1200m², with varying aspect ratios, window wall ratio and lighting controls. Further one reference model is simulated to evaluate the savings in lighting energy consumption for all the major cities in India. Results from the simulated models show an average of 6.27% savings in the annual lighting energy consumption for office buildings in all major cities, due to the advancement of time or shift in occupancy schedule, given that linear lighting controls are applied for all the above models. It is also observed that office buildings in eastern India benefits 2% more than the west.

Presented at: International Building Performance Simulation Association -An IBPSA-AIRAH conference, November 2011, Sydney.
Conference proceedings are available on: http://www.ibpsa.org/proceedings/BS2011/P_1544.pdf

Architectural Curriculum Enhancement for Promoting Sustainable Built Environment in India (2010)

Sanyogita Manu, Anurag Bajpai, Satish Kumar, Rajan Rawal
Abstract: The world today is grappling with the challenge of balancing development through responsible use of natural resources. The challenge only becomes more pronounced for developing economies like India, where improving the quality of life of the masses needs to be mindful of already starved natural resources. To this effect, the advent of clean energy economy is an imminent solution since it has the potential to respond to the challenges and deliver the projected growth in a sustainable way.

To ensure that India is well prepared to transition to a clean energy economy, it needs to review its economic growth indicators in a holistic fashion. Workforce development is perhaps one of the most critical indicators for economic growth. It not only depends on the number of employed workers but also on the skills that they apply and how these skills evolve with the changing context. Education, a strong building block of workforce development, has an important role to play vis-à-vis its application at various levels in the development of a professional and can play a key role in imparting appropriate and contemporary knowledge through continuous curriculum enhancement to cater to the changing professional requirements, offering refresher courses, professional certification programs, vocational training, and other continuous learning programs. Technical education curriculum that supports the foundation of a profession and the ability to enhance it not only provides the required change for today but also establishes a process of evolution that would be able to respond to any subsequent changes in the future. This paper evaluates the potential of curriculum enhancement in the design and construction industry targeting building design professionals. It will discuss a plan proposed by the USAID supported ECO-III project with the support of Bureau of Energy Efficiency, Ministry of Power (India) that reviews the existing structure of the architectural curriculum in India, identifies methods for enhancement and outlines activities that can help in integrating sustainable design practices with the existing educational framework in partnership with the Council of Architecture.

Presented at: ACEEE Summer Study on Energy Efficiency in Buildings, USA, 2010.
Conference proceedings are available on: http://aceee.org/files/proceedings/2010/data/papers/2243.pdf

Hygrothermal performance of lime and cement plaster. (2021)

Nikita Khatri, Rashmin Damle, Rajan Rawal
Abstract: Hygrothermal behavior in materials can impact the energy consumption and thermal comfort of the building space. Commonly, cement plaster is used for plastering surfaces of a building space instead of the traditionally employed lime plaster. With this context, the objective of this study was to evaluate the hygrothermal performance of cement and lime plastered surfaces. To understand the behavior of these materials, two test cells of 1m3 volume having similar construction were developed in Jodhpur, India. The performance of these two plasters was evaluated by carrying out both experimentation and simulation. The test cells were monitored for surface temperature, moisture content, indoor air temperature, relative humidity (RH) and globe temperature. It was observed that the indoor temperature of the lime plastered cell was lesser by 3.1-5.2℃ as compared to the cement plastered test cell. The variation of indoor RH in the lime plastered cell was in the range of 23-60% while the same for the cement plastered cell was 20-65%. Hygrothermal simulations carried out with the Effective Moisture Penetration Depth (EMPD) algorithm showed that the measured and predicted indoor air temperature and RH were in good agreement with a relative difference of 2-4%. In view of the above, the application of lime plaster can be employed as a sustainable measure for energy-efficient buildings.

Keywords: Hygrothermal performance, bioclimatic architecture, lime plaster, India Model for Adaptive Comfort, Effective Moisture Penetration Depth model

Presented at: Comfort At The Extremes, CATE’21, Muscat, Sultanate of Oman, October 2021

Impact of AC Outdoor Unit Placement on Energy Efficiency (2020)

Krishna Patel, Rajan Rawal
Abstract: Growing urbanisation in India has led to the increasing development of high-rise buildings. To maintain the building aesthetics, the outdoor air conditioner (AC) units are stacked within a recessed space. The heat rejected from these outdoor units (ODU) leads to an increase in air temperature of the recessed space. This causes inefficient working of AC units. The paper reports the difference in results when on-site measurement data were compared to CFD simulation results. The on-site measurements were taken for six storeys of an eleven-storey building. The different turbulence models were studied, and it was concluded that the NK turbulence model had the least percentage difference of 8.89% when compared to the site data. Further, NK model was used to study the placement of ODUs in recessed spaces having varying depth and width. When the horizontal distance between the ODUs increased by 1m, maximum condenser on-coil temperatures were reduced by 6°C. The studies concluded that, even by allocating lesser area to the recessed space, but by optimizing the depth and width of the space, the temperature increase of the microclimate can be avoided and AC efficiency can be maintained.

Presented at: Build-Sim Nordic 2020 conference, Oslo, Norway, October,2020

Thermally Activated Furniture: Learnings from Thermal Mannequin and Human Subjects. (2020)

Rajan Rawal, Vishnu Vardhan, Yash Shukla, Arjun Desai
Abstract: This study investigates the effectiveness of Thermally Activated Furniture (TAF) in controlled indoor office environment set up conditions. The TAF included radiantly cooled low‐height vertical partitions placed on the front and to the side of a workstation. The study presents the results of two experiments: the first was conducted using a heated thermal mannequin and the second with help of human subjects. Both experiments were conducted in sequence, using the same experimental facility, referred as the Thermal Comfort Chamber (TCC). The Overall and Local Skin Temperature as well as Heat Flux of the thermal mannequin have been presented. The 22 human subjects were surveyed for their Thermal Acceptance, Sensation, Comfort, and Preference. 16 combinations of TCC Air Temperature and TAF Surface Temperature were investigated for the thermal mannequin and 10 combinations for the human subjects. The Mannequin PMV was compared with the Human AMV. The Cooling Thermal Power of the setup was calculated for all the cases of the Thermal Mannequin study. The results from the two experiments were found to be mutually consistent and indicative of the fact that the TAF operation was effective in providing comfort at indoor air temperatures of up to 28°C.

Keywords: PCS; Radiant Cooling; Thermal Mannequin; Human Subjects.


Assessing the Benefits of Changeover Control Algorithms in Mixed-mode Residential Buildings in India through co-simulation (2020)

Saranya Anbarasu, Yash Shukla, Rajan Rawal, Deepta Mishra
Abstract: Rapid urbanization, rising per capita income and a warming climate are significantly increasing the burden on the electricity grid throughout India (Rawal and Shukla, 2014). The combined use of natural ventilation (NV) and mechanical cooling (MC) systems is a potential solution to provide cooling and thermal comfort to building occupants. Mixed-mode (MM) buildings use NV and MC to provide a comfortable environment for the occupants. Past studies have established that many Indian residences operate in temporal and spatial MM. Existing algorithms used in MM buildings to changeover between NV and MC modes are unsophisticated often leading to inefficient operation. In most cases, the changeover algorithm determines operation mode based on a predefined temperature or based on the occupancy schedule. This paper assesses the benefits of sophisticated changeover control algorithms in a MM residential building. The paper first develops two control algorithms, with varying degrees of complexity, suitable for mixed-mode residential buildings. Further, the benefits of the developed control algorithms are assessed for four climate zones of India using the dynamic thermal simulation model. This paper uses the Functional Mock-up Interface (FMI) to couple Modelica and EnergyPlus as well as to exchange data for co-simulation. The results demonstrate that there is a positive comfort benefit with 76% to 98%lesser uncomfortable hours and 6% to 24% energy savings for the developed algorithms compared to the reference in the 4 climates zones.

Presented at: ENERGISE INDIA 2020, At Hyderabad, India

Hygrothermal Performance of a Building across Different Climates of India (2019)

Rashmin Damle, Rajan Rawal
Abstract: Literature review suggests that building energy consumption is dependent on climatic conditions and hygrothermal characteristics of building materials. This paper summarises the impact of hygrothermal characteristics of building materials on energy consumption in context of five climate zones of India. Numerical simulations of a test building were conducted with and without consideration of moisture transfer through/at walls. EnergyPlus (2016) software was employed for hygrothermal analysis. Moisture absorption at the inner wall surfaces reduces indoor relative humidity. This reduces the heating energy requirement by around 20% for temperate, composite and cold climates. The cooling energy requirement increases in all climate zones but the relative increase is less than 2%.

Presented at: Building Simulation conference held at Rome – Sep 2019

Assessing the Impact of Direct Evaporative Control Algorithms in Mixed-mode Building (2019)

Charalampos Angelopoulos, Malcolm J Cook, Yash Shukla, Efi Spentzou, Rajan Rawal, Luciano Caruggi-De-Fari, Dennis Loveday, Sanyogita Manu, Deepta Mishra, Jayamin Patel
Abstract: Direct evaporative cooling (DEC) is one of the most commonly used cooling systems in many parts of the world with mainly hot and dry climatic conditions. Various simulation-based studies have been conducted to explore the potential of direct evaporative cooling in buildings. However, current dynamic thermal simulation tools use a simplified on/off control approach and do not allow modelling of situations where advanced algorithms are used in controlling DEC units. This paper couples EnergyPlus with Dymola® to simulate and assess the benefits of sophisticated control strategies for DEC units in mixed-mode buildings. This is a novel simulation approach for investigating control of DEC units in buildings that provides great flexibility for investigating future advanced control algorithms. The simulated results suggested that using the proposed sophisticated control algorithms for DEC units it is possible to achieve energy savings up to 35% compared to the base-case scenario and achieve up to 92% comfort hours for Ahmedabad, India. Similar results were predicted for Gatwick, UK.

Presented at: Building Simulation conference held at Rome – Sep 2019

Impact of Thermally Activated Furniture System on Thermal Comfort (2019)

Rajan Rawal, Vishal Garg, Satish Kumar, Bhargav Adhyaru
Abstract: Air-conditioned buildings are conventionally designed and operated to maintain homogeneous thermal conditions. Maintaining the occupied and unoccupied zones at the same thermal conditions leads to higher energy consumption. More importantly, homogeneous thermal conditions do not address the need for individual thermal comfort preferences. A personal comfort system (PCS) allows the occupants to create desired localized thermal conditions around workstations in the office environment. Using computational fluid dynamic (CFD) and multi-node thermo regulation models, this paper evaluates the feasibility of a PCS with a radiantly cooled partition panel system to achieve thermal comfort. All input parameters for the model were derived from real life measurements, including thermal characteristics of the room, work desk with radiantly cooled partition, and HVAC systems. A combination of scSTREAM™ and scTETRA™ was used to model the room and the human body (Cradle MSC Software, 2017). The simulation model had a mannequin in a seated position having summer clothing values and office activity metabolic rate. Combinations of three ambient room air temperatures and five panel surface temperatures were investigated to estimate the impact of radiant panels on overall thermal comfort and various body parts of the mannequin. The body parts like the thighs, chest, back, and pelvis showed a low thermal variation in the range of 0.9-1.2°C. The parts such as the head, neck, shoulders, arms, and legs showed a thermal variation in the range of 1.6-2.7°C, while the body parts farthest from the warm torso - the feet, experienced the highest variation in the range of 4.4-4.5°C. It was observed that the back side of the body was distinctly warmer than the front side of the body throughout the studied cases due to the action of front placed radiant panels. It also indicates that at a given room air temperature with an increase in the difference between surface and air temperature, from 0°C to 8°C, all the body parts experience a reduction in the body part surface temperature.

Presented at: Building Simulation conference held at Rome – Sep 2019

Performance Evaluation of Indirect-Direct Evaporative Cooling System In Hot & Dry Climate (2019)

Shoumik Desai, Rajan Rawal
Abstract: The commercial and residential sector demands high cooling requirement, which is mostly achieved by using conventional cooling systems like split ACs, chillers or VRF. These systems currently produce 100 MT of CO2 per annum and hence contribute significantly to carbon emissions. To mitigate such environmental impacts, using low energy cooling systems like an indirectdirect evaporative cooling system (IDEC) is an energy efficient alternative as it uses energy only for pumping water and blowing air. This study evaluates the cooling performance of IDECs. The wet bulb effectiveness (WBE %) was calculated from the hourly measured values of air temperature (Ta °C) and relative humidity (RH %). These parameters were measured at inlet and supply air. Energy consumption of the IDEC, air blower fan, and water pump were monitored every hour. Thermal comfort surveys were conducted to establish a relation between the effectiveness of IDECs, the cooling energy consumption and degree of occupants’ comfort. ∆Ta of 5- 6 °C and saturation deficit of as 30-35% was observed. During August-October WBE varied from 55-83% with an energy consumption range of 29-30 kWh. Whereas, for November-December, WBE varied from 41-67% with energy consumption range of 23-28 kWh.

Presented at: COMFORT AT THE EXTREMES 2019, At Dubai

A new methodological approach for estimating energy savings due to air movement in mixed mode buildings (2017)

Francesco Babich, Malcolm Cook, Dennis Loveday, Yash Shukla, Rajan Rawal
Abstract: In recent years, there has been a proliferation of air-conditioning in both residential and commercial buildings in India. Mixed mode buildings are buildings in which a combination of air-conditioning and natural ventilation is used to provide comfortable indoor environments. These buildings are likely to be less energy consuming than fully air-conditioned buildings, and further energy savings can be achieved by using air movement to increase the cooling set-point temperature without jeopardizing occupants’ thermal comfort. The aim of this research was to develop and test on a typical Indian apartment a methodology to quantify these energy savings using dynamic thermal simulations. The core of this method is the definition of the cooling set-point, which varies monthly according to the ASHRAE 55-2013 adaptive model. The results show that the annual energy demand for space cooling can be reduced by as much as up to 70 percent by using air motion devices. Moreover, the indoor thermal conditions during the occupied periods predicted by the model are closer to the values measured in field studies in India.

Presented at: Building Simulation Applications 2017, 3rd IBPSA at Bolzano (Italy)

Influence of phase change material on thermal comfort conditions inside buildings in hot and dry climate of India (2016)

Yash Shukla, Rajan Rawal, Nidhi Agrawal, Kaushik Biswas
Abstract: Phase change materials (PCMs) are known for storing thermal energy by the virtue of their inherent latent enthalpies. Careful introduction of PCMs as thermal mass along with external insulation is likely to increase thermal comfort hours in naturally ventilated buildings and reduce cooling energy consumption in air conditioned buildings. Form stabilized phase change materials integrated with building envelope promises to offer ease of construction without encroaching on valuable floor space occupied by building structure. This study evaluates influence of PCMs on thermal performance of buildings in hot and dry climate of India. In first phase, study relied on whole building energy performance simulation to determine potential benefits of phase change materials and to identify suitable thermal characteristics of PCMs. Based on simulation results, two PCM compositions were developed by manufacturer and characterized in the laboratory. Based on measured characteristics, one composition was selected to develop ceiling tile prototype for deployment in experimental setup. In second phase, PCM ceiling tiles were installed in externally insulated naturally ventilated room measuring 3.3 meter by 3.3 meter by 3.3 meter. Fully instrumented room capable of measuring various indoor and outdoor environmental conditions provided insights into PCM effectiveness. Study quantifies benefits of PCM on thermal comfort conditions inside naturally ventilated buildings using simulations and experimental setup. Study also provides guidance to determine most appropriate melting and freezing point of PCM, which helps in manufacturing. A collaborative approach between R&D institute and PCM manufacture provide valuable results leading to understanding of PCM performance in India.

Keywords: Phase Change Building Materials; High Performance Building; Buildings; Thermal Comfort

Presented at: CLIMA 2016

Analytical study on trade-offs between electric light and daylight to achieve energy efficiency (2015)

Saranya S Nair, Rajan Rawal, Agam Shah
Abstract: To provide daylight within a building is an important strategy to improve indoor environmental quality and reduce dependence on electric lighting. Reduction in energy used for electric lighting can be achieved by installing energy efficient lighting system or by increasing presence of daylight. Penetration of daylight can also bring solar radiation and associated heat component inside the building which increase the cooling demand in air-conditioned buildings. Optimum window area, glazing properties and nature of shading devices will help negotiate between availability of daylight and heat ingress due to solar radiation. This study investigates the impact of climate conditions, glazing systems, Window-to-Wall Ratio (WWR), and orientation on energy demand of building. This study is based in context of climates of Ahmedabad, Bengaluru and Chennai. This study was conducted using COMFEN – a tool based on EnergyPlus simulation engine. A case was developed based on business as usual office floor space. Study analyzes spatial pattern of daylight and energy consumption simultaneously.

Keywords: Daylight, Office building, Glazing systems, Window-to-Wall Ratio (WWR), Orientation, Energy Performance Index, Annual Energy Savings, Average Annual Daylight Availability, Spatial Daylight Availability.

Presented at: 7th National Conference on Advances in Energy Conversion Technologies (AECT) at Manipal Institute of Technology, Manipal.

Impact of movable external shading systems on daylight availability of office building in hot and dry climate of India (2015)

Chinmay Patel, Rajan Rawal, Agam Shah
Abstract: As our fast interdepended global world enters the depth of the 21st century, everyone’s immediate attention is to mitigate climate change by various means. One of the proven methods to address climate mitigation is to reduce energy consumption in buildings. The war with global energy crisis is getting intense every second we breathe. Over all buildings account for approximately 40% of global energy consumption (1), most of which is used in making buildings comfortable. Heating Ventilating and Air-conditioning systems (HVAC) and electric lighting does take significan portion of total operational energy consumption. Various materials have influenced architectural aesthetics in recenttimes. Glass is one of them. Uses of glass in fenestration without any shading strategy have adversly affected energy consumption of building. In the current architectural scenario in the country it can be observed that commercial buildings are largely becoming energy intensive in nature, which means that a lot of energy is used in cooling, lighting and running the equipment In this context(2). This study focuses on shading strategy and a solution which meets current requiremeht of architectural aesthestics, possibility of scaling them up and its cost effectiveness. By adding a dynamic shaidng skin over the building’s envelop static skin can lead to drastic reduction in energy loads and increasing thermal and visual comfort at the same time. Keeping materials, finishing and geometry into consideration the design possilities are immense and can indulge the deisgner in varied possibilities. Study provides insight into visual and energy performance of shading devices. The study relies on field measurements and numerical calculations to understand its effectiveness.

Keywords: Daylighting, dynamic shading device, louvers, office building, hot and dry, India,

Presented at: 31st International PLEA Conference. Bologna, Italy. 2015

Daylight Performance Evaluation of Laser cut panel in Office buildings – a case of Indian cities (2015)

Hema Mulchandani, Rajan Rawal, Agam Shah, Charlie Curcija
Abstract: Daylight in office buildings can significantly contribute in lighting energy savings. In addition, daylight improves the occupant’s working environment, performance, health and well-being. Large floor plates for offices accommodates open plan layout, which help to meet contemporary functions of offices. In such cases dependence on electric light increase, leading to higher lighting energy consumption. Limited technologies are available to increase penetration of daylight into the large floor plates. Laser Cut Panels (LCP) is one of the promising technologies, helping reduce electric lighting consumption by illuminating larger floor plates with daylight. This study investigates performance of LCP in three locations in India. Study starts with to develop Bi-directional scattering distribution function (BSDF) to be used within simulation program that assesses the solar and optical performance of LCP. Study relies on combination simulation program such as EnergyPlus for daylight analysis, Ecotect for LCP geometry, Radiance genBSDF for generating BSDF data and visualizations.

A business as usual case of a typical office floor plate was considered as reference model. Three variations in LCP geometry and design, three variations in window to wall ratio, combination of LCP on four orientation of window was investigated. Results generated from simulation run are then analyzed in terms of electric light energy savings and spatial distribution of daylight for different variables.

Keywords: Daylight Performance, Laser cut panel, Bi-directional scattering distribution function
Presented at: 14th Conference of International Building Performance Simulation Association, Hyderabad, India, Dec. 7-9, 2015
Conference proceedings are available on: http://www.ibpsa.org/proceedings/BS2015/p2948.pdf

Assessment of Air Velocity Preferences and Satisfaction for Naturally Ventilated Office Buildings in India (2014)

Sanyogita Manu, Rajan Rawal, Yash Shukla
Abstract: Free-running buildings (i.e. naturally ventilated buildings with no mechanical systems for heating or cooling) have the potential to be much more energy efficient than air-conditioned buildings. This paper is based on approximately 3200 instantaneous thermal comfort and 1500 long term background survey datasets from a large scale field study conducted in free-running Indian office buildings. Responses to air movement satisfaction and air movement preference questions, together with concurrent measurements of indoor environmental parameters of air and globe temperature, relative humidity and air velocity are used for this study. The paper gives an insight into the operation of ceiling fans and windows, and the range of air velocity experienced by office workers in free-running office buildings. It gives the relationship between measured indoor air velocity, concurrent air and globe temperature and relative humidity. Instantaneous responses are correlated with the on-site observations on window and ceiling fan operation, as well as indoor environmental measurements. The assessment of preferred air velocity from ceiling fans and operable windows as an adaptive measure in this paper contributes to the development of better designed free-running office buildings in India.

Presented at: 30th International PLEA Conference, December 2014, Ahmedabad
Conference proceedings are available on: http://www.plea2014.in/wp-content/uploads/2014/12/Paper_7C_2720_PR.pdf
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Relevance of radiant cooling in Indian context (2014)

Srijan Kumar Didwania, Rajan Rawal, Yash Shukla, N. K. Bansal
Abstract: The benefits of radiant space cooling system over conventional Variable Air Volume (VAV) space cooling system with reference to economics, system operation, installed capacity, energy consumption and human thermal comfort has been studied. This study was carried out for commercial office buildings in four climate zones of India. EnergyPlus energy simulation program was used for this study. The study incorporates the Life Cycle Cost analysis (LCCA) approach to demonstrate the benefits of radiant system over the conventional VAV system. LCC provides a better long term cost assessment of a project alternative over its complete life cycle, including initial capital costs, maintenance costs, operating costs and cost or benefit of eventual disposal, than other economic methods that focus only on first costs or operating costs in the short run. With acute peak load deficit and load shedding prevalent in many parts of India, this paper also demonstrates the effect of radiant cooling on operative temperature along with thermal comfort during the grid power outage period. This principle could find a place in the office buildings of India where cooling system is either shut down or switched to diesel-generator-power during unavailability of power from the grid.

Presented at: International ASHRAE Conference for Hot Climate, At Doha, Qatar
Conference proceedings are available on: http://www.techstreet.com/standards/relevance-of-radiant-space-cooling-in-indian-context?product_id=1876442

Plug Load Consumption in Typical Commercial Offices in India (2014)

Mithi Dave, Rajan Rawal
Abstract: The increasing penetration and diversity of plug loads and their ubiquitous nature in work environments in India means that they are potentially significant consumers of electricity. End-use energy efficiency measures in buildings have largely ignored plug loads which might be attributed to a dearth of India-specific studies which quantify plug-load energy consumption and their usage characteristics through end-use measurements. Field studies in 30 typical offices covering a total floor space of 8000 m2 and 1160 plug loads were carried out to find plug load consumption characteristics. The study shows plug loads as significant consumers of electricity and reveals wide gaps in design and actual on-site provision for these loads that need to be addressed. The study also quantifies the contribution of standby power from major plug loads found in offices.

Keywords: plug loads, measurements, end-use, offices, standby power

Presented at:'4th Master’s Conference - PEOPLE and BUILDINGS' at Sir John Cass Faculty of Art, Architecture and Design, London Metropolitan University, UK
Conference proceedings are available on: http://nceub.org.uk/mc2014/proceedings/MC2014_proceedings_People_and_Buildings_2014.pdf

Analysis of Daylighting Devices for Office Buildings of New Delhi, India (2009)

Neha Singhal, Tanmay Tathagat, Rajan Rawal
Abstract: Deep plans have become a common practice in multi-storey buildings’ designing and large open plans have become the preferred choice in order to have flexibility of the space and economic benefits. However, the deep core areas of these buildings cannot be naturally illuminated by side windows, and therefore, such areas depend entirely on electricity for illumination. The work done n the present study is an attempt to find out the benefits of using daylight device technologies to enhance natural illumination of deep plan office buildings. The focus of this study is to determine appropriate passive daylight device for office buildings in the city of New Delhi, India, and helps to understand the barriers that prevent harnessing in the daylight to its maximum potential. This study takes into account the prevailing building typologies in the commercial sector. Four hypothetical models have been derived subsequently by analyzing the existing office buildings typologies of the city. After developing the hypothetical models, various windows to wall ratios have been applied to understand the availability of daylight in these models. The study addresses to three daylighting devices which are available in the international market – light shelves, Anidolic light ducts, Light tubes. The integration of selected devices with the hypothetical models has been considered for more than one scenario, which studies and examines its appropriateness for daylight usage. This entire exercise has been carried out using validated simulation program. The formulation of the simulation exercise has been established on the available weather data. Experiments have been carried out under sunny sky conditions and CIE overcast sky. The exercise also evaluates the cost effectiveness of the integration of daylight device within existing buildings to increase daylight availability and thereby reduced energy loads because of artificial lighting systems. Hence it tries to assess the cost effectiveness of application of such devices. The study demonstrates the technical & economic viability of passive daylight devices in the context of New Delhi, India.

Presented at: International Building Performance Simulation Association (IBPSA) at Glasgow – 2009.
Conference proceedings are available on: http://www.ibpsa.org/proceedings/BS2009/BS09_1685_1692.pdf

Occupant interaction with external shading system in residential buildings of Ahmedabad (2021)

Snowy Christophel S, Minu Agarwal, Rajan Rawal
Abstract: As per the United Nations International Strategy for Disaster Reduction (UNISDR) during the last two decades heat waves accounted for 5.6% of the all the disaster related global fatalities. Several cities have established heat wave management task forces that warn and prepare people for upcoming heat waves by various mitigation strategies and advisories. With rising average temperature, occupant controlled passive design measures such as external movable shades can serve as resilience measures to improve indoor thermal environmentunder extreme heat. However, their effectiveness in doing so is highly dependent on timely deployment by the building occupants. This study focusses on understanding the occupant behaviour in operating external movable bamboo roller shades installed in balcony projections of residential buildings in Ahmedabad, India (hot and dry climate zone). The study was carried out during February and March of 2021 at four mid-rise residential buildings. The position of shades for each façade were recorded daily to examine the activity levels of the occupants. 65% occupants were found to be non-users, that is, they did not operate the shades during the entire observation period. Among the occupants that did choose to operate the shades (14% active and 21% passive users), outdoor temperature, sun exposure duration and solar radiation incident on the façade were found to have significant effect on the occlusion rates. The high percentage of non-users, while based on observations under moderate weather conditions raises questions whether passive design measures could be used reliably by occupants to improve indoor conditions under adverse weather conditions in an effective manner. At the same time users’behaviour in terms of occlusion rates (degree of shade closure) was found to be affected by weather and sun exposure related variables.

Keywords: Occupant interaction, External movable shades, User proportion category, Passive resilience

Presented at: Comfort At The Extremes, CATE’21, Muscat, Sultanate of Oman, October 2021

Evaluating the energy-saving potential through occupant interaction with the external fenestration (2021)

Amanda Cassiana Santiago and Rajan Rawal
Abstract: Occupant's interaction with the external fenestration has a large impact on the indoor environment and energy consumption of buildings. The rapid increase in India’s residential cooling demand requires a better understanding of mixed-mode operations in residential buildings. This study attempts to understand occupant behaviour for window operation.
This study has been divided into three stages. Stage I- a survey was conducted with 150 occupants to identify the non-thermal drivers that prevented the opening of windows during a favourable outdoor environment. The first part of stage II consists of a field mapping study in which ten residences were monitored for five days. The parameters monitored were humidity, temperature, CO2, window operation and window status. The second part of stage II was the experimental stage to determine the window status by finding the air change rate through the tracer gas experiment. In this experiment, the CO2 decay curves were analysed with various opening percentages; the curves were cross-referenced with the occupant-generated CO2 data to define the window status. Stage III- is Computer simulation, which assisted in identifying the ideal period for which windows could be operated. The possible energy saving was established by analysing the comfort hours. The data collected on-site was used in modelling and simulation. The window operation schedule was fed into the simulation model and simulated for two cases. The study concluded that in 90% of observed residences the window operations were under the influence of non-thermal drivers. This resulted in a 20% reduction in thermal comfort hours which in turn increases the energy costs by 30%.

Keywords: occupant interaction, fenestration, energy saving

Presented at: Comfort At The Extremes, CATE’21, Muscat, Sultanate of Oman, October 2021

Guidelines to bridge the gap between adaptive thermal comfort theory and building design and operation practice (2020)

Runa T. Hellwig, Despoina Teli, Marcel Schweiker, Joon-Ho Choi, M.C. Jeffrey Lee, Rodrigo Mora, Rajan Rawal, Zhaojun Wang, Farah Atrash
Abstract: Adaptive thermal comfort guidelines have been developed within the work of Annex 69: “Strategy and practice of adaptive thermal comfort in low energy buildings”. The guidelines have been established based on a framework for adopting adaptive thermal comfort principles in building design and operation developed by the authors. The guidelines target building practitioners, addressing the critical interrelated role building planners, building operators and occupants play. A successful adaptive thermal comfort design, in which design for human thermal adaptation is foreseen, planned, and carefully embedded in the design and operation intent, is based on broad knowledge and understanding of the multiple quantifiable and non-quantifiable factors influencing human perception, as well as human building interaction. Adaptive building design follows a user-centric integrated design approach and therefore it is critical to consider the occupants’ and the operators’ role in buildings already in the design phase. This paper focuses on three main challenges identified earlier and how these are addressed in the guidelines, i.e. i) updating prevailing knowledge about human thermophysiology and adaptation, ii) developing a procedure for design of adaptive opportunities, and iii) providing guidance for operational planning and operation of adaptive buildings. The challenge for future research remains to assess the magnitude of how specific design decisions affect particular adaptive mechanisms.

Keywords: Adaptive thermal comfort, Personal control, Building energy efficiency, Climate context, Integrated Design, Occupant, Stakeholder


Applying adaptive principles: Developing guidance for planning practice (2019)

Runa T. Hellwig, Despoina Teli, Marcel Schweiker, Joon-Ho Choi, M.C. Jeffrey Lee, Rodrigo Mora, Rajan Rawal, Zhaojun Wang, Farah Atrash
Abstract: One of the major challenges of building industry today is to provide indoor spaces allowing the occupants to make themselves comfortable while achieving low energy consumption. Considering the observed increasing temperatures and a more extreme climate, this becomes even more urgent and difficult to accomplish. It is therefore necessary to rely on approaches than contribute to sustainable building design, such as the adaptive approach to thermal comfort which postulates that people are not passive recipients of their environment but adapt behaviourally, physiologically and psychologically. The concept of adaptive thermal comfort was formulated many decades ago and has been validated in numerous field studies. Temperature thresholds based on adaptive models have been included in international and national standards. However, the overall understanding of how to translate the adaptive principles into design practice and concepts for operating buildings is still limited. Subtask B of IEA Annex 69 addresses this gap: "Strategy and practice of adaptive thermal comfort in low energy buildings". The subtask aims to develop guidelines for low energy buildings that include the principle of adaptive comfort. This paper discusses the challenges and gaps identified in using the principles of adaptive thermal comfort in building design and operation and outlines the contents of the imminent guideline.

Presented at: CATE 2019 – Comfort at the Extremes: Energy, Economy and Climate, At Heriot Watt University, Dubai

Thermal Comfort and Energy Use of Affordable Housing in Ahmedabad, India (2019)

Garima Kamra, Sanyogita Manu, Rajan Rawal, Tithi Soladhara
Abstract: Housing for all – 2022’, a large-scale housing initiative was launched in 2015 by the Indian government for providing quality affordable housing to the lower economic segment by the year 2022. Occupant thermal comfort is one of the significant aspects of liveability and applies to affordable housing as well. These houses have low energy consumption as of now, however as incomes and comfort expectations increase, energy use and related costs in this segment are expected to surge. So far, comfort field studies in affordable houses in India remains a subject largely neglected. This paper reports findings of the thermal comfort conditions and energy use of 20 houses in three affordable housing developments located in Ahmedabad, India during winter season (November-February). The analysis discusses results from data collected using three methods - Long-term monitoring of household energy use and indoor environment parameters of temperature and relative humidity, instantaneous measurements of thermal comfort conditions and right-here-right-now thermal comfort surveys. It is observed that average daily energy use ranges from 0.5 - 6.75 kWh and is dependent on appliance ownership and occupant behaviour and is base load driven in these houses. 66% of the occupants reported being comfortable in their thermal environment during the survey period. The conclusions from this study will be of meaning to various stakeholders in the affordable housing segment.

Presented at: CATE 2019 – Comfort at the Extremes: Energy, Economy and Climate, At Heriot Watt University, Dubai

Energy & Thermal Comfort Performance Evaluation of Net Zero Energy Building in Hot Dry Climate-A case study (2019)

Rajan Rawal, Yash Shukla, Sanyogita Manu, Himani Pandya, Agam Shah, Amiya Ranjan, Vishnu Vardhan
Abstract: The paper presents the case study of a Net-Zero Energy Building (NZEB) located within the CEPT University campus, Ahmedabad. It starts with a narration on design and construction and provides an overview of the building envelope characteristics and operational strategies. Custom design and operation of the building management system (BMS) in order to synchronize the electrical consumption and generation using solar PV is described. The paper analyses the energy consumption and generation in NZEB during 24 months of operation (Jan-2017 to Dec-2018). Hourly end use energy consumption and generation data were analyzed to understand the performance of the envelope and electro-mechanical systems. Along with energy consumption analysis, the paper also includes the study of occupant comfort. The occupant comfort data was correlated with the hourly outdoor weather data collected using an automated weather station installed at the NZEB. This paper is an attempt to share the learnings in regard to the design, construction, operation, and maintenance of the NZEB in India.

Presented at: CATE 2019 – Comfort at the Extremes: Energy, Economy and Climate, At Heriot Watt University, Dubai

Evaluation of Ventilation Metrics for Naturally Ventilated Spaces From Flow Patterns Generated in a Water Table Apparatus (2019)

Pooja Mundhe, Rashmin Damle, Prasad Vaidya
Abstract: Wind driven ventilation in buildings is an effective way of diluting the indoor air for maintaining thermal comfort and acceptable indoor air quality. Visualization of wind induced flow patterns in a building with a water table apparatus is a relatively easier method producing instantaneous results. This work focusses on quantifying the flow patterns obtained from the water table experiments in terms of ventilation metrics like percentage of dead spots, absolute ventilation efficiency, and air changes per hour. These metrics will aid in making design decisions in terms of appropriately orienting the building, sizing, and placing of openings in the building.

Presented at: Building Simulation conference held at Rome – Sep 2019

Design Charts to Assist on the Sizing of Natural Ventilation for Cooling Residential Apartments in India (2019)

Luciano Caruggi de Faria, Malcolm Cook, Dennis Loveday, Charalampos Angelopoulos, Yash Shukla, Rajan Rawal, Sanyogita Manu, Deepta Mishra, Jayamin Patel
Abstract: This paper presents four design charts (DC) to work as a simplified, easy-to-use and cost-effective tool to assist architects and building designers on sizing openings to deliver natural ventilation (NV) for cooling. The DC are derived from analytical techniques for four NV design systems based either on buoyancy-driven or wind-driven flow. The application of the DC is demonstrated to size NV openings for a bedroom in an apartment located in three Indian cities for two opening size scenarios: ‘business as usual’ (A); and ‘necessary size’ (B) to deliver the desired ventilation rates for cooling. The ventilation rates for cooling found with these DC are compared with outputs from computational fluid dynamics simulations. Findings show that for the earlier design stage the derived DC are effective tools. It is also found that the opening sizes used in scenario A do not deliver the desired NV rates for cooling, whilst the openings for scenario B must be sized separately for each city to be effective.

Presented at: Building Simulation conference held at Rome – Sep 2019

Determining the Most Appropriate Form of Urban Building Energy Model for the City of Ahmedabad (2019)

Pamela Jane Fennell, Paul A Ruyssevelt, Rajan Rawal, Veeren Poola
Abstract: A review of existing large-scale building energy models was undertaken, highlighting their prevalence at geographically higher latitudes. The ability of these models to adequately represent cities in the global south is questionable and existing classifications are inadequate to describe the diversity of models that have been developed. As a response, a novel model classification scheme was developed to explore how the various models capture the underlying physical context, and to assess their appropriateness for application to the city of Ahmedabad in western India.

The model classification scheme was used to develop a characteristic map for the new model of Ahmedabad and define priorities for the model’s development.

Presented at: Building Simulation conference held at Rome – Sep 2019

Evaluation of Daylight Performance Using a Calibrated Daylight Model (2019)

Vasudha Sunger, Prasad Vaidya
Abstract: This study uses calibrated simulations to evaluate the daylight performance of the new workshop building at CEPT University, Ahmedabad, India, and to validate Lighstanza as a daylighting simulation tool. The methodology included field measurement and calibrating a daylight model. The calibrated model of the building has an RMSE (Root mean square error) and an NMBE (Normalised mean biased error) of less than 4%. The building was found to be LEED v4 and Energy Conservation Building Code 2017 (ECBC) compliant. The current manual switching response to daylight saves € 1,066 per year. The Daylight Glare Probability analysis showed that the spaces experience glare issues only between 5-6 PM during the summer months.

Presented at: Building Simulation conference held at Rome – Sep 2019

What do the traditional pol houses teach us for contemporary dwellings in India? (2017)

Rajan Rawal, Devarsh Kumar, Sanyogita Manu
Abstarct: Indian real estate is trying to find appropriate solutions to provide thermally comfortable dwellings using passive design strategies. Historically, a big part of architectural teaching has been focused on learning about climate responsive strategies from vernacular buildings. However, such knowledge sharing was based more on observational studies as opposed to long-term scientific field studies with quantitative outcomes. The authors believe rigorous scientific enquiry is required to understand the performance of vernacular dwellings in order to encourage the use of climate responsive strategies. This study looks at the vernacular dwellings, called pol houses, as well as the contemporary dwellings to assess their thermal comfort performance. Indoor environmental conditions in these houses were monitored hourly for a year. Outdoor conditions were also recorded using a weather station simultaneously. Selected dwellings were compared on the basis of area, occupancy and socio-economic background. Thermal performance of these houses was evaluated against two models – the India Model for Adaptive Comfort (IMAC) and the ASHRAE Standard-55 adaptive model.

Keywords: Vernacular dwellings, Contemporary dwellings, Climate responsive design, India Model for Adaptive Thermal Comfort, Ahmedabad
Presented at: PLEA 2017 Edinburgh, Design to Thrive
Conference proceedings are available on: http://nceub.org.uk/PLEA2017/proceedings/PLEA2017_proceedings_volume_I.pdf

Building Bridges or Chasms? Separating energy efficiency education for better integration (2017)

Sanyogita Manu, Prasad Vaidya, Rajan Rawal
Abstarct: India is witnessing a buzz of activity to promote energy efficiency in buildings at national and regional levels. These efforts range from policy measures, international programs, training courses and educational programs, research projects, advocacy programs by various organizations to individual efforts to design, construct and operate energy efficient buildings. Lack of technical knowledge and capacity building has often been cited as one of the most important barriers to achieve real results. Due to the rapid increase in construction, it is imperative that energy efficiency be integrated seamlessly with the current industry practices. With that aim, multiple efforts have been made to integrate sustainable building design education with the existing architectural curriculum – if it has to be integrated in practice, it needs to be integrated in academics. This, however, has not proven to be a successful strategy, primarily because architecture curricula are set and there is an inertia to change what has worked for decades. This paper presents a detailed case study of a post graduate program in Building Energy Performance at one of the premier architecture and design universities in India. In doing so, it establishes the need for a paradigm shift and offers an alternative pathway of a specialized education curriculum and pedagogical approach, by introducing a new credible building professional into the design team who takes responsibility of the energy performance.

Presented at: PLEA 2017 Edinburgh, Design to Thrive
Conference proceedings are available on: http://nceub.org.uk/PLEA2017/proceedings/PLEA2017_proceedings_volume_II.pdf

Performance evaluation of climate responsive buildings in India: Two case studies from hot-dry and composite climate zones (2017)

Sanyogita Manu, Gail Brager, Ann Dennis
Abstract: India has a rich tradition of climate responsive architecture throughout its five distinct climate zones. Designing climate responsive buildings is challenging, requiring an understanding of building physics, as well as the manner in which buildings are designed, constructed and operated in a given cultural context. The process becomes more difficult with the ever-increasing comfort expectations. This paper is based on a study that was initiated in 2013 to evaluate the thermal performance of climate responsive buildings in a quantitative way. Several modern institutional and office buildings in warm-humid, hot-dry, moderate and composite climate zones, where a wide range of passive and hybrid design strategies was deployed were monitored. Two of these case studies are presented in this paper to evaluate the performance of solar chimney with evaporative cooling and cavity walls. In addition to the measured variables, performance was compared using a calculated ‘comfort exceedance’ metric derived from the neutral temperatures calculated from the India Model for Adaptive Comfort (IMAC).

Presented at: PLEA 2017 Edinburgh, Design to Thrive
Conference proceedings are available on: http://nceub.org.uk/PLEA2017/proceedings/PLEA2017_proceedings_volume_III.pdf

Impact of compliance to Annual Solar Exposure requirements as per LEED v4 on Fenestration Design for Indian Context (2017)

Agam Shah
Abstract: Good daylight is an important aspect of building design. Various metrics have been developed to predict annual daylight performance using Climate Based Daylight Modelling (CBDM). However, National Building Code (NBC) and Energy Conservation Building Code (ECBC) of India do not require compliance using CBDM. LEED (Version4 BD+C) requires compliance using Spatial Daylight Autonomy (sDA300/50%) and Annual Sunlight Exposure (ASE1000,250h) based on IES LM-82-12. Up to 3 points can be scored in LEED version4 based on achieved sDA but compliance to ASE, which predicts the potential for visual discomfort due to exposure to direct sunlight, becomes mandatory and hence critical. ASE not only depends on the position of the sun but also on dynamic climatic conditions, which is highly challenging while designing and predicting performance of fenestration during preliminary design stages. The research provides a matrix of Projection Factor (depth) required for external shading for deep plan (9m and 12m) office spaces, four orientations and seven geographical locations in four climate zones of India. This matrix will help architects to make informed decisions at initial design stage before conducting detailed simulation. The research also makes important observations in the way ASE changes for various cases and points out practicalities of design.

Presented at: PLEA 2017 Edinburgh, Design to Thrive

Impact of surface modulation on solar heat gain: A performance evaluation of brick cantilevers/overhangs in brickwork (2017)

Gargi Priyamwada, Rajan Rawal, Rashmin Damle
Abstract: Reducing solar heat gain to achieve thermal comfort and energy efficiency in building is one of the key strategies adopted by architects in cooling dominated climate. Brick trellis and brick masonry wall are some visual expressions explored by architects. This study investigates the impact of surface modulation due to projections in brickwork on total solar heat gain. Brick projecting out from a wall creates shadows on the wall itself. This study attempts to understand the combined and cumulative effect of the heat transfer through conduction, convection, and radiation. A comparative analysis is made between plain brick-wall and brick-walls with projections. The primary objective of this study is to develop an equation to quantify the reduction in heat gain due to surface modulation. To restrict the scope of this study equatorial latitude is chosen as the geographical location and year round solar heat gains is calculated. Preliminary observations from the study suggest that an increase in the surface area has a direct relation with heat gain through conduction. However, the convection helps to reduce surface temperature and the micro-shading pattern created due to brick projections help to reduce the solar gain

Presented at: PLEA 2017 Edinburgh, Design to Thrive
Conference proceedings are available on: http://nceub.org.uk/PLEA2017/proceedings/PLEA2017_proceedings_volume_II.pdf

Passive Design Indices: Quantifying the Potential of Passive Design Strategy in a Climate (2017)

Jaydeep Bhadra, Prasad Vaidya, Saket Saraf
Abstract: The study focuses on developing indices to assess the potential for passive cooling strategies for a climate. Diverse microclimatic conditions are found within broader climatic regions at the scale of a few kilometers. Currently available climate analysis tools do not explore the interrelationships between different climatic parameters. Earlier work showed that it is possible to develop a weather-data-based classification to map the potential of some basic passive design strategies, such as building orientation. This study takes that approach forward to establish weather-data-based indices for advanced passive design strategies such as evaporative cooling, comfort ventilation, radiant cooling, earth cooling, and night ventilation. Weather data variables are identified for each strategy. Adaptive thermal comfort models represent the indoor comfort conditions. TMY weather data of 59 Indian cities and 2 international cities are analyzed to develop the indices. Thermal Autonomy and Discomfort Degree Days are the metrics developed to measure the potential of the passive strategies. These will enable policy makers to develop climate zone maps that highlight the potential for specific low energy solutions in a region.

Keywords: Passive design, Indices, Climate, Potential, Low energy cooling.
Presented at: PLEA 2017 Edinburgh, Design to Thrive
Conference proceedings are available on: http://nceub.org.uk/PLEA2017/proceedings/PLEA2017_proceedings_volume_III.pdf

Understanding the Differences of Integrating Building Performance Simulation in The Architectural Education System (2017)

Christina J Hopfe, Veronica Soebarto, Dru Crawley, Rajan Rawal
Abstract: In order to assist tertiary architectural education institutions as well as the architecture profession in developing course material and training packages related to Building Performance Simulation (BPS), we present the outcome of a survey conducted in Australia, India, the US and the UK. The main objective of the survey was to investigate how BPS is taught at a number of different architecture schools at universities in these countries and to point out potential difficulties and barriers. Based on the survey, the paper proposes a number of recommendations and highlights opportunities for future degree schemes that develop module content and learning objectives/ outcome for teaching BPS at architectural tertiary educational institutions.

Presented at: Building Simulation conference BS 2017 (IBPSA) at San Francisco, USA in August 2017
Conference proceedings are available on: https://www.conftool.pro/bs2017/index.php/BS2017_Education_02_2_1319_Hopfe_2017-03-08_04-08_a .pdf?page=downloadPaper&filename=BS2017_Education_02_2_1319_Hopfe_2017 -03-08_04-08_a.pdf&form_id=1319&form_version=final

Calculating the Effect of External Shading on the Solar Heat Gain Coefficient of Windows (2017)

Christian Kohler, Yash Shukla, Rajan Rawal
Abstract: Current prescriptive building codes have limited ways to account for the effect of solar shading, such as overhangs and awnings, on window solar heat gains. We propose two new indicators, the adjusted Solar Heat Gain Coefficient (aSHGC) which accounts for external shading while calculating the SHGC of a window, and a weighted SHGC (SHGCw) which provides a seasonal SHGC weighted by solar intensity. We demonstrate a method to calculate these indices using existing tools combined with additional calculations. The method is demonstrated by calculating the effect of an awning on a clear double glazing in New Delhi.

Presented at: Building Simulation conference BS 2017 (IBPSA) at San Francisco, USA in August 2017
Conference proceedings are available on: https://www.conftool.pro/bs2017/index.php/BS2017_Windows_03_3_1769_Kohler_2017-05-09_11- 59_a.pdf?page=downloadPaper&filename=BS2017_Windows_03_3_1769_Kohler_2017-05-09_11-59_a.pdf&form_id=1769&form_version=final

Codes and Beyond – A View from Around the World (2017)

Dimitri Contoyannis, Lori McElroy, Rajan Rawal, Paul Banniste
Abstract: This panel discussion will look at how practitioners around the world use energy simulation tools to demonstrate code compliance, and to meet other beyond code programs. Participants from four different continents provide a world-view of energy analysis by discussing location-specific processes, tools, metrics, etc.

Presented at: Building Simulation conference BS 2017 (IBPSA) at San Francisco, USA in August 2017

Opportunities and Challenges in Monitoring the Thermal Performance of Passive Buildings in India (2016)

Sanyogita Manu, Rajan Rawal, Gail Brager, Chinmay Patel
Abstract: In the context of climate change, reduction in operational energy of buildings has gained a prominent focus amongst researchers and practitioners. India and the U.S. have both used design strategies to provide comfortable indoor environments with no or marginal reliance on conventional energy sources, but often with significant differences in their approaches and historical context. In particular, certain locations in both countries offer opportunities to design and operate buildings that are naturally ventilated or mixed-mode (combining operable windows and mechanical cooling). Historical or vernacular case studies have provided empirical evidence of climate responsiveness; however the lessons learned have not been deployed in the mainstream. Absence of rigorous performance evaluation might be one of the reasons behind the lack of large scale deployment of such design strategies. This paper documents the challenges and lessons learned from an extensive monitoring study undertaken in India. It forms a part of a larger project that aims at formulating a set of protocols of such field monitoring activity and evaluating the performance of selected passive strategies. Observations were made for each stage of monitoring, from building selection to data quality assurance. We found that many buildings were not necessarily constructed or operated as originally designed vis-à-vis the passive strategies we were studying. In some cases the physical components of passive strategies were not maintained properly. Our experience also emphasizes the importance of having a local champion in the building being monitored. We realized the significance of understanding the trade-offs between the quality and extent of instrumentation as well as the value of allowing flexibility in the monitoring plan to make real-time changes on site.

Presented at: 2016 ACEEE Summer Study on Energy Efficiency in Buildings
Conference proceedings are available on: http://aceee.org/files/proceedings/2016/data/papers/3_578.pdf#page=1&zoom=auto,-13,731

The role of air motion for providing thermal comfort in residential / mixed mode buildings: a multi-partner Global Innovation Initiative (GII) project (2016)

D. Loveday, M. Cook, G. Brager, E. Arens, H. Zhang, R. Rawal, K. Vadodaria, P. Cropper, L. Webb, F. Babich, R. Cobb, R. Ariffin, S. Kaam, V. Foldvary, P. Verma, L. Toledo
Abstract: As the climate changes, global use of air-conditioning will proliferate as solutions are sought for maintaining thermal comfort in buildings. This rises alongside increased purchasing power as economies grow, harbouring the potential to unleash an unprecedented growth in energy demand. Encouraging higher levels of air movement at warmer temperatures to maintain thermal comfort may offset the risk of increased air-conditioning use. Whilst laboratory studies have quantified air motion effects on the human body, it remains unclear as to how best to incorporate higher air motion in the design and operation of residential / mixed mode buildings to offset air-conditioning use. The project reported is developing a better understanding of thermal comfort in residential /mixed mode buildings and is identifying the potential for higher air movement for providing energy-efficient comfort. Co-ordinated field surveys in British and Indian residences of thermal conditions, sensations and air motion practices have been conducted. The data generated will contribute to a worldwide database, and will inform validation of a coupled thermal comfort / airflow model for designing comfortable, energy-efficient indoor environments that exploit higher air motion. This paper describes the overall project, and presents preliminary findings from the British residential field survey.

Keywords: Thermal Comfort, Residential/mixed mode, Field Studies, air motion, database
Presented at: 9th International Windsor Conference, 7th - 10th April 2016, Cumberland Lodge, Windsor Great Park, UK
Conference proceedings are available on: http://nceub.org.uk/W2016/pdfs/proceedings/Proceedings_Windsor_Conference_2016.pdf

Clothing insulation as a behavioural adaptation for thermal comfort in Indian office buildings (2016)

Rajan Rawal, Sanyogita Manu, Yash Shukla, Leena E. Thomas, Richard de Dear
Abstract: Regulating clothing is one of the most obvious behavioural responses to changing thermal conditions. The extent of clothing, in turn, affects thermal sensation and acceptability. A lack of extensive thermal comfort field studies in India has meant that there has been very limited data on clothing related occupant behaviour in Indian offices until now. This paper aims to understand clothing norms and practices in Indian offices using data gathered via an extensive field study of thermal comfort in India. It uses the office occupants’ response to thermal sensation, acceptability and preference questions as experienced “right here, right now” from more than 6000 surveys together with simultaneous measurement of environmental conditions, clothing and metabolic activity. These surveys are administered in five climate zones across three seasons in air-conditioned, naturally ventilated and mixed mode buildings. The paper analyses clothing insulation as a behavioural response to changes in the environment. The variation in clothing insulation with observed indoor and outdoor temperature is analysed for different seasons, building types and cities. The study also examines the extent of behavioural regulation in clothing between the male and female office workers. The results suggest that women tend to wear lower clothing insulation on an average in summer compared to men. In naturally ventilated and mixed mode buildings, variability in clothing insulation was higher compared to air conditioned buildings, emphasizing the role of clothing as an adaptive measure.

Keywords: Clothing, Behavioural adaptation, Thermal comfort, Indian offices, Office users
Presented at: 9th International Windsor Conference, 7th - 10th April 2016, Cumberland Lodge, Windsor Great Park, UK
Conference proceedings are available on: http://www.nceub.org.uk/W2016/pdfs/proceedings/Proceedings_Windsor_Conference_2016.pdf

Occupant feedback in air conditioned and mixed-mode office buildings in India (2016)

Sanyogita Manu, Chinmay Patel, Rajan Rawal, Gail Brager
Abstract: India has a largely cooling dominated climate where space cooling accounts for approximately 31% of the energy consumed by commercial buildings. Deeper market penetration of air conditioning systems, higher income levels driving higher comfort expectations, and growing floor space have led to a steep rise in associated carbon emissions. India needs to adopt an energy efficient regime in which governments, businesses and individuals transform the way buildings are designed, built and operated, while still maintaining high levels of occupant satisfaction.

Two diverse approaches are practiced in India to achieve energy efficiency. The first relies on passive design strategies based on traditional wisdom. The second relies on high-performance HVAC building conditioning systems. Most Indian climate zones offer opportunities to design and operate buildings as naturally ventilated or mixed-mode. But such design practices need to be promoted on the basis of scientific studies related to occupant behavior, comfort and associated energy consumption.

This paper evaluates occupant satisfaction in a mix of consciously-designed air conditioned and mixed-mode buildings based on online surveys, and limited physical measurements. The survey includes questions about thermal comfort, indoor air quality, air movement, acoustics and adaptive controls such as windows and fans. The paper offers an understanding about the perception and behavior of occupants in mixed-mode buildings in various climate zones of India to help identify strategies to promote efficient mixed-mode buildings in both India and other regions.

Keywords: Occupant satisfaction, Post-occupancy evaluation, Mixed-Mode buildings, Thermal comfort, Indian offices
Presented at: 9th International Windsor Conference, 7th - 10th April 2016, Cumberland Lodge, Windsor Great Park, UK
Conference proceedings are available on: http://www.nceub.org.uk/W2016/pdfs/proceedings/Proceedings_Windsor_Conference_2016.pdf

Capturing the views of architects about building performance simulation to be used during design processes (2015)

Veronica Soebarto, Christina J. Hopfe, Dru Crawley, Rajan Rawal
Abstract: In the past 30 years, much effort has been directed to make building performance simulation become inherent in architectural practice. Anecdotal evidence however shows that it still a long way for this goal to be achieved. This paper presents the outcome of a survey conducted in Australia, India, the US and the UK, to investigate difficulties that architects have to overcome in their day-to-day practices and identify the reasons why using building performance simulation, regardless how friendly the tools are, is still not and may never be in the mainstream of their practices. Based on the survey, the paper proposes a number of recommendations to overcome this challenge in line with IBPSA’s vision on bridging the gap between research and practice.

Presented at: 14th Conference of International Building Performance Simulation Association (IBPSA), Hyderabad, India, Dec. 7-9, 2015.
Conference proceedings are available on: http://www.ibpsa.org/proceedings/BS2015/p2790.pdf

Divide by net-zero: infinite potential or calculation error? A quasi-academic design and construction project in India (2015)

Rajan Rawal, Prasad Vaidya, Sanyogita Manu, Yash Shukla
Abstract: This paper traces the conceptualization, design development and construction process of a net-zero energy building (NZEB) in a university campus in India. Climate resilient and high performance building design warrants an integrated design process with front-loaded analysis to arrive at an optimized solution through an iterative method. The building discussed in this paper is designed to work as a living-laboratory where the architectural elements and systems components have a degree of flexibility built-in to allow for experimentation with different systems and operation strategies. A team formed under a US-India bilateral project with expert consultants from across the world and local consultants’ experiences in execution proposed a highly optimized yet, context-appropriate solution. An iterative process and exchange of ideas between a master architect, a design, construction and commissioning team that would eventually occupy the building, other consultants, and equipment and material suppliers worked together in the evolution of the building design. The design of the comfort systems and energy monitoring systems for the building form an important demonstration of the collaboration between academia and industry which is not a usual practice in India. The building, in general, serves as an example of the challenges and opportunities that integrated design offers and this paper elaborates on some of the important lessons for all stakeholders – architecture students, professionals, researchers and industry, who are going to play a vital role in the making of high performance buildings in future. The paper highlights the experiences during the design detailing, construction and equipment sourcing, that prove challenging to smaller NZEBs in developing economies.

Keywords: NZEB, High performance buildings, Integrated design process, Developing economies, India
Presented at: 31st International PLEA Conference. Bologna, Italy.2015.

The Triple Bottom Line Benefits of Climate-Responsive Dynamic Façades (2014)

Rajan Rawal, Vivian Loftness, Rohini Srivastava, Devanshi Dadia, Hetal Parekh, Agam Shah
Abstract: To achieve net zero energy, façade designs must move from static dark glass monoliths to dynamic, climate responsive layers for balancing daylighting and shading, natural ventilation and mixed mode conditioning. While 5-15 year energy paybacks are sufficient to prompt some level of increased investment in facades, dynamic facades require the addition of triple bottom line (TBL) calculations that capture the economic, environmental and human benefits of high performance buildings. This paper introduces an approach to TBL justifications of climate-specific high performance building façade solutions, to provide professionals and manufacturers compelling arguments for inspiring building investment that will improve the quality of the indoor environment. Given that lighting and space conditioning are 80% of office energy loads in India, arguments for investing in façades that optimize daylighting and shading, natural ventilation and mixed mode conditioning are critically needed. This paper illustrates the triple bottom line of five climate-responsive façade and related system improvements – high visible transmission/ low solar glass, internal light shelves/inverted blinds, daylight dimming, external overhangs/shades, and operable windows - that demonstrate TBL paybacks of less than two years for new and retrofit construction. This ongoing project is funded by the US Department of Energy and LBNL, and undertaken in collaboration with CEPT, India through the Center for Building Energy Research and Development (CBERD).

Presented at: 30th International PLEA Conference, December 2014, Ahmedabad
Conference proceedings are available on: http://www.plea2014.in/wp-content/uploads/2014/12/Paper_6A_2790_PR.pdf

Occupant Feedback in Energy-Conscious and ‘Business as Usual’ Buildings in India (2014)

Anoop Honnekeri, Gail Brager, Sanyogita Manu, Rajan Rawal
Abstract: Buildings account for 30% of energy consumption in India, and it is estimated that 70% of the projected commercial building stock by 2030 is yet to be built. The recently established five-year US-India Centre for Building Energy Research and Development (CBERD) project aims to address the barriers for adopting low energy consuming strategies in buildings in India, while exploring the lessons that can also be applied to the US context. This paper evaluates the performance of two energy-conscious (EC) and two ‘business as usual’(BAU) buildings in Ahmedabad, India using a combination of physical measurements, and a web-based occupant survey. The survey includes questions about Indoor Environmental Quality (IEQ): thermal comfort, indoor air quality, air movement and acoustics; it also asked questions about adaptive controls such as windows and fans. The EC buildings performed well in many categories compared to the ‘business as usual buildings’. One of the EC designed buildings in particular performed exceptionally well compared to the CBE database which consists of over 600 buildings mainly from the US but also from 9 other countries. In the other three buildings, dissatisfaction prevailed mainly with acoustic quality and office layout due to lack of speech privacy and visual privacy, but this is common across the larger database. More than 70% occupants were satisfied with thermal comfort in all except one of the BAU building and of the occupants who were uncomfortable mostly cited air movements being too low as the reason for discomfort.

Presented at: 30th International PLEA Conference, December 2014, Ahmedabad
Conference proceedings are available on: http://www.plea2014.in/wp-content/uploads/2014/12/Paper_7C_2707_PR.pdf

Evaluating the Performance of Naturally Ventilated Brick and Lime Domes and Vaults in Warm-humid Climate in South India (2014)

Rajan Rawal, Mona Doctor-Pingel
Abstract: India has a rich tradition of passive architectural design practice. There has been, however, little effort to study these design strategies to evaluate their effectiveness. This study analyses the climate responsiveness and thermal performance of domes and vaults in brick masonry. The study compares the performance of hemispherical domes and segmental vaults in a residence-office building for indoor conditions measured on hourly basis for one year. The study gives the necessary quantifiable performance of domes and vaults constructed using low-cost, local materials as an effective energy efficient design strategy that may be easily adopted as a practice.

Presented at: 30th International PLEA Conference, December 2014, Ahmedabad
Conference proceedings are available on: http://www.plea2014.in/wp-content/uploads/2014/12/Paper_5E_2721_PR.pdf

Impact of native evergreen trees on the visual comfort in an office space in Ahmedabad, India (2014)

Ankit Bhalla, Sanyogita Manu
Abstract: This study investigated the impact of native evergreen trees on the daylight availability in office spaces in Ahmedabad, India. An evergreen tree, native to the hot and dry climate of Ahmedabad, was selected and its impact on daylighting in interior spaces is analyzed compared to a no-tree scenario. The distance of the tree from the window was varied to examine parameters such as contrast and brightness at the task plane for the equinox and solstice days. Desktop Radiance 2.0, which is a backward ray tracing daylight simulation software, was used, followed by a calibration study. Uniform and sunny sky conditions based on Ahmedabad climate data were considered. The results indicate that trees can be very effective in achieving visual comfort in conditions of harsh sunshine outdoors. The type of tree is of more importance for visual comfort than the distance between the tree and the window. The evergreen tree performed well to mitigate visual discomfort. Careful selection of the tree type and its positioning on the southern facade reduced illuminance levels but helped improve visual comfort by almost 50%. This study also explains in detail the method used for determination of Leaf Area Index and Leaf Area Density used for calculating the crown density of the tree, which may help future work attempting to study the impact of vegetation on the thermal or visual performance of building envelope.

Presented at: 30th International PLEA Conference, December 2014, Ahmedabad
Conference proceedings are available on: http://www.plea2014.in/wp-content/uploads/2014/12/Paper_1A_2247_PR.pdf

Understanding the trade-offs between thermal comfort and energy consumption in Air Conditioned office spaces in India (2013)

Sanyogita Manu, Yash Shukla, Rajan Rawal
Abstract: This study aims to establish a correlation between thermal comfort and energy consumption for typical office buildings in India. Building envelope characteristics are varied to represent local energy code compliant case. Regression analysis is used to derive the aforementioned correlation using energy consumption and thermal comfort indices from the simulation output. The results from this study will assist designers to understand the energy implications of improving thermal comfort, both in terms of comfort hours as well as PMV. This paper is also aimed at supporting some of the field observations from post-occupancy surveys currently being done in India that indicate a preference of temperatures higher than what conventional practice dictates and make the case for more responsible control of indoor environments.

Presented at: 13th Conference of International Building Performance Simulation Association, Chambéry, France, August 26-28
Conference proceedings are available on: http://www.ibpsa.org/proceedings/BS2013/p_1514.pdf

Effect of Surface Reflectance on Lighting Efficiency in Interiors (2011)

Rohini Singh, Rajan Rawal
Abstract: The paper attempts to analyze the relationship between surface color reflectance and lighting power density for a given set of context. Analysis was based on digital modeling using validated energy simulations tool. The study establishes itself on this premise. The exercise elaborates evaluating the impact of vertical and horizontal planar interior elements’ surface reflectance & examines its impact on LPD. This is done through different scenarios derived from the base case. All derived scenarios were then confirmed to the established standard of visual comfort. The result was collated to develop a chart illustrating the finding.

Presented at: International Building Performance Simulation Association -An IBPSA-AIRAH conference, November 2011, Sydney
Conference proceedings are available on: http://www.ibpsa.org/proceedings/BS2011/P_1725.pdf

Air Conditioning, Comfort and Energy in India’s Commercial Building Sector (2010)

Leena E. Thomas, Richard de Dear, Rajan Rawal, Ashok Lall, PC Thomas
Abstract: Before India’s building sector can fulfil its CO2 abatement potential, it is imperative for new build projects, especially those which provide for commercial and public functions, to eschew the energy-intensive designs that characterized western commercial buildings of the 20th century. In the absence of an adaptive thermal comfort standard specifically for India’s climatic and cultural context, the current trend is simply to design air-conditioned buildings to meet the stringent ASHRAE and ISO “Class A” comfort specifications. This paper proposes a holistic Post Occupancy Evaluation (POE) study of a cross section of Indian office buildings purposively stratified across a range of energy intensities with diverse environmental control systems and design approach in different climatic zones to develop an adaptive thermal comfort standard. By climatically adapting indoor design temperatures, the standard will offer India a low-carbon development pathway for its commercial building sector without compromising overall comfort or productivity.

Key words: climate change mitigation, adaptation, thermal comfort, India
Presented at: NCEUB Conference, Adapting to Change: New Thinking on Comfort Cumberland Lodge, Windsor, UK, 9-11 April 2010. London: Network for Comfort and Energy Use in Buildings
Conference proceedings are available on: https://opus.lib.uts.edu.au/bitstream/10453/16603/1/2010000752.pdf

Impact of Window Design Variants on Lighting and Cooling Loads: Clues for Revisiting Local Building Regulations (2009)

Sanyogita Manu, Rajan Rawal
Abstract: The study is placed within the context of local building regulations in India. Building regulations, for fenestration in general and window openings in particular, are, to a large extent, ambiguous in nature. In the context of India, observations show that the regulations specify window size for the sole purpose of ventilation whereas windows are major role-players in the thermal and daylighting performance of buildings. In this paper, parametric simulation is used to generate data for cooling and lighting loads for typical commercial office spaces in the hot-dry climate of Ahmedabad, India. This data is then analysed using Multiple Regression techniques to express loads as a function of floor area, aspect ratio, window-to-wall ratio and orientation of windows. The equations derived from regression help compare the energy implications of varying window sizes and their orientations. The observations and results stress the need to re-analyse local building regulations as they fail to indicate the maximum allowable limit of window size leading to highly inefficient building design.

Presented at: International Building Performance Simulation Association (IBPSA) held at Glasgow – 2009
Conference proceedings are available on: http://www.ibpsa.org/proceedings/BS2009/BS09_0286_293.pdf

Supported by:

Ministry of New and Renewable Energy Govt. of India, Gujarat Energy Development Agency, U.S. Agency for International Development iNDEXTb (Industrial Extension Bureau) Govt. of Gujarat, Shakti Sustainable Energy Foundation, New Delhi