Rajan Rawal

CEPT University | CEPT · Center for Advanced Research in Building Science and Energy (CARBSE)

Far from being a panacea, air-conditioning is shown to create social, environmental and economic problems. Alternatives to air-conditioning are identified as a key means of reducing energy demand and carbon emissions, improving resilience to heat, and providing a healthy indoor environment. These alternatives are more than a technological issue and...

This study quantifies the gap between net-zero energy and net-zero carbon through a life cycle assessment (LCA) of a net-zero energy building (NZEB) in Ahmedabad, Gujarat, India. The annual net-zero energy evaluations of a building do not account for the greenhouse gas (GHG) emissions released before the building operation phases. Nor does it accou...

Rapidly developing economies of countries in hot climates face the risk of a significant increase in CO2 emissions. This study developed strategies for low energy cooling and ventilation for Indian residences (LECaVIR). Ventilation and cooling techniques were developed and tested for India’s four climatic zones. The analysis shows that natural vent...

Indian residences are vulnerable to heat-driven discomfort amid the mounting prevalence of weather extremes, residential design and construction practices, and densifying urbanscapes. Therefore, it is vital to understand the thermal comfort characteristics of nationwide residences. This study proposes an adaptive thermal comfort model based on year...

Traditional buildings since many centuries have used lime as a binder and finishing material. However, in contemporary construction practices, lime mortar and lime plaster have been replaced by cement mortar and cement plaster. Lime is a sustainable and self-healing material whose strength increases with time. In addition to its pleasing appearance...

In warm and hot climates, ceiling fans and/or air conditioners (ACs) are used to maintain thermal comfort. Ceiling fans provide air movement near the skin, which enhances the evaporation of sweat, reduces heat stress, and enhances thermal comfort. This is also called the cooling effect. However, AC usage behaviour and the effects of elevated air sp...

On average, India has more than 3000 Cooling Degree Days (CDD). The multifamily public housing being constructed under India’s Prime Minister Awas Yojana (PMAY) scheme 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 s...

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 in-doors to the occupants. This stud...

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....

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 lim...

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 advis...

RACs are increasingly being adopted as a standard method of active cooling with the modernisation of small and medium-sized commercial and residential spaces in India. However, current standards and labels only provide a partial evaluation of RAC performance. This study targets three aspects of RAC performance in energy, comfort and environmental i...

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 relations...

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 establi...

Urban building energy models (UBEM) are driving sustainable design and operations of cities by combining urban datasets with energy simulations. UBEMs are developed from a range of inputs on the spatial and semantic details of the buildings, and the systems affecting their energy performance. Large geographical scales with finer spatio-temporal det...

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. H...

Efficient service delivery in the Municipal Solid Waste Management sector by default implies regular waste removal from the habitation to a treatment or disposal facility. In the 21st century, such service delivery in large cities demands on the deployment of motorised vehicles for the transport of waste. However, the ULBs in India remain oblivious...

The Central Business District (CBD) of Ahmedabad in India, planned to be developed by 2040, will have increased floor space, three times of what it is in 2020. This will double the cooling energy demand if contemporary practices are followed. This research aims to develop building envelop retrofit strategies which minimize the lifecycle cost and th...

The advancement in the field of Urban Building Energy Modelling (UBEM) is assisting urban planners and managers to design and operate cities to meet environmental emission targets. The usefulness of the UBEM depends upon the quality and level of details (LoD) of the inputs to the model. The inadequacy and quality of relevant input data pose challen...

Traditional building design education in the disciplines of building services, civil engineering, mechanical engineering, etc. focusses on quantifiable factors, i.e. factors which can be subject of calculation, simulation and dimensioning. Since non-quantifiable factors are not part of calculation or simulation models, there is a tendency that they...

In recent times, the building sector has experienced a proliferation of air-conditioned spaces leading to higher operational energy consumption. Reduction in operational energy for buildings is seen as one of the effective measures to limit long-term climate change. Air-conditioned buildings are conventionally designed and operated to maintain homo...

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 withing a recessed space. The heat rejected from these outdoor units (ODU) leads to increase in air temperature of the recessed space. This causes inefficient working of...

Database of the thermophysical properties of forty-two samples of solid masonry building units and nine non-homogeneous walling technologies from various Indian states/climatic zones.

Personalized Comfort Systems (PCS) have been seen as an effective alternative to provide thermal comfort along with reducing energy consumption. This paper contains the methodology and results of a study conducted in a laboratory environment that aims to evaluate Thermally Activated Furniture (TAF) panels. These panels mounted in front and on the s...

The objective of this study is to assess low-carbon and cost-effective solutions for achieving deep cuts in space cooling requirement and associated cooling electricity demand from India’s urban residential sector during 2020–2050.

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 t...

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...

Rajan Rawal introduces listeners to fundamental principles in climate-responsive building design and explains how an evaluation of a building should include energy and thermal performance. By taking various buildings designed by architects in India, he maps how architects have adopted multiple approaches to climate 'responsiveness'. The podcast c...

Thermal comfort research has been traditionally based on cross-sectional studies and spatial aggregation of individual surveys at building level. This research design is susceptible to compositional effects and may lead to error in identifying predictors to thermal comfort indices, in particular in relation to adaptive mechanisms. A relationship be...

With great growth, comes a great need for power. And now, more than any other time in our planet’s history, we need to act swiftly to save our future. As more and more people spend time inside commercial buildings worldwide, as well as in India, the buildings have to maximise their energy efficiency. The best starting point to increase the number o...

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 li...

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...

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...

Conventional heating, ventilation, and air-conditioning (HVAC) systems are designed to condition the entire building volume. In contrast, Personal Comfort Systems (PCS) target conditioning only the occupied zones of the space, while maintaining the remaining volume at a relatively under-conditioned state. PCS offer the occupants the choice of modul...

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 persona...

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 respon...

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 respon...

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 app...

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 refrigera...

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...

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...

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...

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...

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...

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...

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 syste...

The ever-increasing demand for built spaces to cater to the needs of the tropical population compels for the adoption of sustainable building forms and passive design strategies. This research aims at studying the cases of six naturally ventilated occupied buildings constructed in the tropical ‘warm and humid’ climate of Pondicherry and Auroville,...

The buildings are conventionally operated to maintain homogeneous indoor ambient conditions to maintain comfortable thermal and visual environments. However, maintaining these homogeneous conditions throughout the building leads to unnecessary energy consumption, and does not address the varying thermal and visual comfort needs of the individual oc...

India has a rich tradition of climate responsive architecture, incorporating several variations of passive design strategies that have been layered over time with the cultural, social and environmental context of the immediate geographical region. Designing climate responsive buildings is challenging, requiring an understanding of building physics,...

The potential of mixed-mode office buildings with varying design and control parameters is examined by using an uncertainty analysis in the three climate zones of India. The analysis is in terms of cooling energy consumption, thermal comfort conditions, and natural ventilation hours. Furthermore, influential parameters are identified using sensitiv...

India’s cooling energy needs are projected to grow significantly within the next decade, with far reaching environmental and societal impacts. The Government of India (GoI) has elevated addressing India’s cooling challenge as a national priority and is actively engaged in developing a National Cooling Action Plan. A recent study by Alliance for an...

India’s cooling energy needs are projected to grow significantly within the next decade, with far reaching environmental and societal impacts. The Government of India (GoI) has elevated addressing India’s cooling challenge as a national priority and is actively engaged in developing a National Cooling Action Plan. A recent study by Alliance for an...

Providing thermal comfort to building occupants is very important to the health and wellbeing as well as productivity. Hence, it may necessitate the use of air conditioning during hot season. Use of conventional air conditioning systems like split AC to achieving thermal comfort is continuously increasing in India. This also increases the electrici...

The study focuses on residential characterization of ECBC at city/state levels. It tries to use Overall Thermal Transfer Value (OTTV) as performance criteria other than the Energy Performance Index (EPI). As EPI only shows the energy usage index of that building, but it lacks the ability to define which factors in the building are leading to higher...

Energy Conservation Building Code (ECBC) sets minimum standards for the design and construction of buildings. It (ECBC) promotes the energy efficient design or retrofits of the buildings without affecting their functions, comfort, health and productivity. It also serves appropriate regards for economic considerations of the building by lowering the...

This paper puts India’s unprecedented growth of building energy demand, and efforts to curb it, into an international context by adapting the reporting criteria developed for the Global Status Report on Buildings & Construction to the India context. The paper also presents a survey of state and non-state actor climate commitments submitted to the U...

India’s growth of energy demand in the building stock, and efforts to curb it, are placed into an international context by adapting the reporting criteria developed for the Global Alliance on Building & Construction's (GABC) Global Status Report (2017) on buildings and construction. A survey of state and non-state actor climate commitments submitte...

Recognizing the value of open-source research databases in advancing the art and science of HVAC, in 2014 the ASHRAE Global Thermal Comfort Database II project was launched under the leadership of University of California at Berkeley's Center for the Built Environment and The University of Sydney's Indoor Environmental Quality (IEQ) Laboratory. The...

The total electricity consumption from commercial sector was about 9% during 2013–14 in India. Load research survey was carried out to study the usage patterns for all types of electric appliances used in commercial establishments at income, appliance and end-use levels in Gujarat state of India – one of the most progressive states. Penetration lev...

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 eff...

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 to...