ECBC – Residential Building Energy Code



Growing demand for Energy and the implication in generating more energy to meet the demand of the consumers, towards the climate and environment is cause of great concern around the globe. Major countries around the world have taken up series of initiatives voluntarily to reduce the energy demand and conserve energy through sustainable approach. India’s Intended Nationally Determined Contributions (INDC’s) aim to reduce the emission intensity of its gross domestic product (GDP) by 33 to 35% by 2030, from 2005 level. It is a very ambitious target for India, considering that we just achieved complete electrification of all villages. But, the timing cannot be more perfect. India is at the cusp of modernization of its infrastructure and a guideline in which these developments should have will determine the energy demand for the future. Any effort to achieve this target is contingent upon the increase in efficiency of energy use across all sectors, especially in the building sector. As per Energy Statistics 2018 report, 30% of yearly electricity consumption in India is through building sector. While Industrial Sector still remains at the top of energy consumption table, it won't take long for building sector to become the largest emitter of greenhouse gases (GHGs).

It would be surprising for many to note that 75% of energy consumption in building sector is from residential buildings, and it’s been increasing rapidly in the recent years. 

There various factors that play important role in driving this consumption. Although access to electricity has increased recently, but it is the intensity of usage that drives the consumption. Air conditioners which are largely decentralized in the residential units are one of the major contributors towards the spike in consumption. And rising global temperature due to climate change, is forcing more and more people to use air conditioning to use frequently to achieve thermal comfort in their homes. It is only a matter of time, before residential sector becomes the dominant contributor of GHG emissions in India. 

India being in cooling-dominated climates zone, where ambient temperatures are high during the major part of the year and mechanical cooling is required for thermal comfort, heat gain index is not given much importance in residential building design. Hence, there is a large variation in the current practices in building design and sensible cooling demand. 

ECO Niwas Samhita 2018, is an Energy Conservation Building Code for Residential Buildings (ECBC-R), launched by Ministry of Power in 13 December 2018. The aim of the code is to benefit the occupants and the environment by promoting energy efficiency in design and construction of homes, apartments and townships. The code is prepared after extensive consultation with all stakeholders, consisting of architects & experts including building material suppliers and developers. Bureau of Energy Efficiency (BEE), which is statutory body under Minister of Power, whose objective is to implement policy and programmes in energy efficiency and conservation. 

It is to be noted that there are lot of awareness programmes across India, which spreads information on energy usage and how to reduce it through simple steps. But the adoption rate is very low. For instance, BEE advice consumers to turn on their AC degree by 24 degree Celsius, through various digital and offline campaigns. But, still many consumers, go for the lowest temperature settings in AC, which is both unhealthy and consume twice as more electricity than running it an optimum level. Energy Codes are regulatory measures for ushering energy efficiency in the building. Codes like this are particularly relevant for countries like India, where more than 70% of infrastructure need for the country is yet to be built. ECBC code for commercial sector has already been implemented in many buildings across India and it is providing excellent savings to the developers and occupants in long run. Many states have mandated ECBC code in commercial sector, which provides guidelines to make the buildings more energy efficient and sustainable for the future.

Eco Niwas Samhita, or ECBC-R, main objective how to make this code as simple as possible, to increase widespread adoption throughout the country. So, for the first stage of ECBC-R, the envelope aspect of the building is considered and it is envisaged new parts will be added to address other aspects, such as energy efficiency of equipments for building operation, renewables etc. Building envelope has the highest impact on thermal comfort, and consequently on the energy use in residential buildings. The envelope is also a permanent component of the building with the longest life cycle. Through ECBC-R, the design and construction of new residential building stock being built currently and in near future, thus significantly curtailing the anticipated energy demand for comfort cooling. 

To keep the code simple and easy to implement among the residential sector, the code require only simple calculations based on inputs from architectural drawings of the buildings. The code does not require any advance simulations and can be used by architects and engineers at ease to enhance their envelope design. BEE also provides tools for calculations to check whether envelope meets the criteria, in their website to make it easier to do compliance check. The intent of the code is to set minimum performance standards for building envelope to limit heat gains ( for cooling dominated climates ) and limite heat loss ( for heating dominated climates ) through it. 

ECBC - Residential 

In ECBC-R, Residential building includes buildings in which sleep accomodation is provided for normal residential purposes with or without cooking or dining or both facilities. Individual homes, which have total sleep accomodation not more than 20 persons, and apartment houses which include building structure in which living quarters are provided for three or more families, living independently of each other and with independent cooking facilities. 

The following building structure are excluded from residential building segmentation in the code :

  1. Lodging and rooming houses : which have separate sleeping accommodation on transient or permanent basis, such as inns, clubs, motels and guest houses.
  2. Dormitories : which has group sleeping accommodation, with closely associated rooms under join occupancy and single management. 
  3. Hotels : either single building or group of buildings under single management, in which sleep accomodation is provided. 

Aspects of ECBC - R :

Though Building Envelope is the main aspect of Phase 1 of ECBC-R code, but there are mandatory or minimum requirements on various other areas within the building to ensure that energy efficiency and thermal comfort factor are being considered during design and construction.

Fresh Air Compliance :

Ventilation being important aspect of thermal comfort, ECBC-R recommends the openable window-to-floor area  (WFR op) ratio to be operable area to the carpet area of dwelling units. Openable area includes all windows, ventilators which has opening direct to the external air, and also open balcony such as verandah, corridor or shaft. Interestingly doors opening into corridors are not considered. This ratio suggested is the minimum compliance requirement by ECBC-R, which helps in fresh air ventilation of the project, improvement in thermal comfort and reduction in cooling energy. 

Daylight Compliance :

Adequate daylight into frequently used parts of the house, will decrease the frequency of artificial lighting requirement. Being in tropical climatic zone, we receive abundant of daylight throughout the year and making effective use of this, will ensure energy efficiency in our day to day activities. Visible Light Transmittance (VLT) is the ratio of total transmitted light to the total incident light. It is measure of the transmitted light in the visible portion of the spectrum through a material.

ECBC-R recommends specification of glass used in non - opaque building envelope  shall comply with requirements below

Roof Performance Compliance :

Roof act as the layer between the indoor and external climate and plays an essential role in the overall performance of the building. Reducing the heat gain or losses from the roof, will help in improving the thermal comfort in the indoor environment and thereby reducing the energy required for cooling or heating through mechanical ventilation. Thermal performance of the roof is categorized by Thermal transmittance and the maximum value of thermal transmittance will be 1.2 W/m2.K


Residential Envelope Performance :

Apart from roof, which absorbs most of the heat, the envelope of the building gains significant amount of heat, through the walls, floor, windows etc. 

Residential envelope heat transmittance (RETV) is the net gain rate (over the cooling period) through the building envelope (excluding roof) of the dwelling units divided by the area of the building envelope (excluding roof) of the dwelling units. Heat conduction through opaque and non opaque building envelope components such as wall, opaque panels in doors, windows, ventilators, and solar radiation. Minimum RETV for building envelope in Hot-Dry Climate zone of 15 W/m2.

The code requires various inputs from the architectural design drawings of residential buildings and requires to do simple calculations to meet the required compliance value to be compliance for ECBC-R certification. 

Implementation and Challenges : 

ECBC ( Commercial ), which was launched in 2007 by BEE, to streamline the guideline norms in construction of real estate space, which had unprecedented growth rate throughout urban India. The problem with ECBC code under EC ACT 2001, is that till date it remains voluntary code with no mandates in most of the states in India. ECBC-R also has the same challenges, that it might take years, before they become mandatory in most of states. 

Telengana was the first state in the country to make ECBC Commercial code mandatory for all commercial or non residential buildings with plot area of 1000 sq.m or built up area of 2000 sq.m to comply with ECBC code for both design and construction in Greater Hyderabad Region. After many years of being voluntary code, finally developers took the code seriously because of the mandatory laws of the state. Subsequently, Conserve Consultants has did the First ECBC Compliance project in Telangana State and started to encourage our clients in the region to be more aware of the ECBC code and implementation.

From our experiencing in implementing ECBC code for our clients, we often ask why we seem to be oblivious of the imminent rising demand for energy by the building sector and why we need to take urgent corrective step to address this challenge. Buildings have predominantly remained dormant and municipal councils do not have singular governing body to look at the resource consumption footprint of buildings in the state. We all have building bylaws that cover floor area ratio, ground coverage, projects, etc, but no definite bylaws for natural ventilation or daylighting for that matter. No strict reinforcement from any state council to ensure the type of energy efficiency options the building should adopt. Although we know by fact that interventions in design and development, could improve the building performance and reduce the energy consumption close to 50%, there were no checks and balances for the developers, architects or engineers to ensure that these norms are followed. ECBC code will continue to remain elusive and many urban local bodies are clueless on how to implement it. Unless there is integration of functions of urban local bodies such as municipality, utility companies etc and capacity enhancement of people responsible for implementation and monitoring, it shall remain a challenge. 

India needs a robust implementation framework for both ECBC-R and ECBC-C to holistically address the building sector and its growing resource needs. Integration has to happen at policy level as well as on ground level. Immediate attention is required to enact bylaws and expanding its boundary to include energy, water, air quality, material and construction techniques as the new norm for buildings in both residential and commercial sector and make it mandatory in all states.  Unless these codes remain as voluntary practice, implementation of codes will remain a lost opportunity for our country.

Case Study of ECBC-C Implementation : 

Implementation of ECBC takes place at two stages of project development 

  1. Design Stage
  2. Construction Stage

Certifications are awarded at both the stages to ensure and keep track of all the changes that has been promised in the design stage, has been followed in the construction stage. To achieve compliance for the project, we can either approach as 

  1. Prescriptive Method
  2. Whole building performance method

Difference between prescriptive and whole building performance method is, In prescriptive method, all energy aspect of the building is considered as individual components and are measured against the AHU value for minimum performance requirement. In Whole building performance methods, entire building is stimulated to ensure that the energy performance of the building meets the baseline criteria of code. Once the criteria of code are matched, certifications are issued based on the different stage of the project.The certification also contains several stars to indicate the level of adoption of sustainable aspects in the project, where 2 star compliance is mandatory for the project. 

In this project, Aparna IT park, in Hyderabad Region, we did whole building performance approach to ensure that the performance of the building is at its peak capacity. Once we did simulation of the building, we proposed changes in the design to enable the building to meet the ECBC code criteria. 

Original Design :

Block A :

Block B : 

Modified Design : 

Block A :

Block B : 

Technical Aspect of Project : 

Comparison between Modified Design vs the Original Design

The table shows the modifications we proposed for the original design, to make sure that the building meets the best possible performance. Some of the notable changes include, 

  1. Increase insulation in the roof with 50 mm efficient roof insulation materials.
  2. Replace regular glass with DGU glass in the facades and fenestration of the building.
  3. Increase the indoor lighting through simulation and lux requirement.
  4. Modify HVAC Design to ensure that it runs at optimum performance.

Through the guideline process in ECBC code implementation, the client was able to reduce the energy requirement of the building from 6.5 Million kWh/yr to 5.5 Million kWh/yr, resulting in the savings of 15% above ECBC baseline earning TS - 3 Star rating for the building.


Author profile : 

Mr. Vijayakumar S, is one of the few BEE accredited Master Trainers for Energy Conservation Building Code (ECBC). He also have contributed towards developed of ECBC-Residential Code. Vijay was also awarded with “Top 50 Most Talented Sustainability Leaders in India” by World CSR day. He is a partner and heads technical division at Conserve Consultants Pvt Ltd.