1.1 India’s aim is to reduce the emissions intensity of its gross domestic product (GDP) by 33 to 35 percent by 2030 from 2005 level. Any effort to achieve this target is contingent upon the increase in efficiency of energy use across all sectors, especially in the building sector. The building sector in India consumes over 30% of the total electricity consumed in the country annually and is second only to the industrial sector.
1.2 As per Energy Statistics 2020 released by Ministry of Statistics and Programme Implementation (MoSPI), total energy demand by various sectors for FY 2018–19 is about 569.5 Mtoe1, out of which residential (domestic) sector consumes about 52.04 Mtoe, which is 9.1% of total primary energy consumption.
1.3 Energy codes for new buildings are an importantThe total electricity demand for FY 2018–19 is about 1158 Billion Units (BU)2. Domestic sector consumes about 280 Billion Units which is about 24.2% of total electricity consumption. The energy demand in the domestic sector has been on the rise since the late 2000s, with increasing demand for appliance ownership, especially of fans and televisions in urban and rural areas, and an increase in refrigerators and air conditioners in urban areas. Electricity consumption increased from 146 BU in 2009- 10 to 280 BU in 2018-19 with CAGR of 6.74%.
1.4 It is estimated that, domestic sector will consume about 769 TWh3 of electricity and 98.6 Million toe 4of energy in 2031. Out of the total electricity consumed in the building sector, about 70% is consumed in the residential buildings.
1.5 According to India Cooling Action Plan, approximately 8% of the current households have room air conditioners. This is anticipated to rise to 21% and 40% in 2027- 28 and 2037-38 respectively. The demand for air-conditioning will continue its exponential growth with improvement in household incomes and will become the dominant contributor of GHG emissions nation-wide owing to increased electricity consumption. This situation calls for an immediate energy conservation action plan.
1.6 Energy Conservation Building Code – ResiEnergy codes for new buildings are an important regulatory measure for ushering energy efficiency in the building sector. Eco Niwas Samhita 2018 (Part-I: Building Envelope) was launched in 2018 to set minimum building envelope performance requirements to limit heat gains (for cooling dominated climates) and to limit heat loss (for heating dominated climates), as well as for ensuring adequate natural ventilation and daylighting potential.
1.7 TThe Eco Niwas Samhita 2021 (Code Compliance and Part-II: Electro- Mechanical and Renewable Energy Systems) is a code specifying code compliance approaches and minimum energy performance requirements for building services, indoor electrical end-use and renewable energy system.
1.8 The code also provides following five appendices which are recommendatory in nature
and envisaged to be added in future revision of the code.
2.1 The purpose of Eco Niwas Samhita 2021 (Code Compliance and Part-II: Electro- Mechanical and Renewable Energy Systems) (hereinafter referred to as ‘ENS-C&2’ ) is for code compliance and to provide the minimum requirement(s) for building services, electro-mechanical and renewable energy systems for new residential buildings
2.2 The code applies to –
2.3 The code is also applicable for all additions made to existing residential buildings where the existing building exceeds the threshold defined in section 2.2 of the ENS-C&2. For this purpose, the addition together with the existing residential building is required to show compliance with ENS-C&2 with the authority having jurisdiction
2.4 The code is also applicable for all alterations made to existing residential buildings where the existing building exceeds the threshold defined in section 2.2 of the ENS-C&2 and the alteration, part of the building or its system, is been done for an area more than 1000 square feet. For this purpose, the part of the building or its systems that are being altered is required to show compliance with ENS-C&2 with the authority having jurisdiction.
2.5 The code sets minimum requirement for all building envelope parameters as mentioned in Eco Niwas Samhita 2018 (Part I: Building Envelope).
2.6The ENS-C&2 sets minimum requirements for electro-mechanical systems used in building services (i.e. common area and exterior lighting, elevators, pumps, basement ventilation, transformers, power distribution losses, power factor correction, electrical vehicle supply equipment etc.) and indoor electrical end-use (i.e. indoor lighting, comfort systems, service hot water etc.).
2.7 The ENS-C&2 sets minimum requirements for renewable energy systems (Solar hot water requirements and Solar Photovoltaic) integration.
2.8 If a building project has more than one building block in multiple orientations, then compliance must be sought by showing that building block meet the performance requirements in each of the four-cardinal orientation (north, south, east, west). However, for identical building blocks with the same orientation, the compliance must be shown for one building block.
2.9 TThe following codes, programs, and policies will take precedence over the code in case of
conflict:
3.1.1 In order to demonstrate compliance with the code, the building shall comply with all of the mandatory requirements stated in Chapter 4 along with either of the two approaches
3.1.2 Table 1 below gives the minimum ENS score required to be obtained as per eligible project category:
Project Category | Minimum ENS Score |
---|---|
Low rise buildings | 47 |
Affordable Housing | 70 |
High rise buildings | 100 |
3.1.3 Low Rise Buildings: A building equal or below 4 stories, and/or a building up to 15 meters in height (without stilt) and up to 17.5 meters (including stilt).
3.1.4 Affordable Housing Projects: Affordable houses are Dwelling Units (DUs) with Carpet Area less than 60 sqm. It also includes Economically Weaker Section (EWS) category and Lower Income Group (LIG) category (LIG-A: 28-40 sq. m. and LIG-B 41-60 Sq.m.). For details, refer chapter 7.
3.1.5 High Rise Buildings: A building above 4 stories, and/or a building exceeding 15 meters or more in height (without stilt) and 17.5 meters (including stilt).
3.1.6Compliance for Mixed Mode Buildings
3.1.7 Prescriptive Method
3.1.8 Point System Method
Section | Components | Minimum points | Additional points | Maximum points |
---|---|---|---|---|
6.4 | Building Envelope Building Envelope |
47 | 40 | 87 |
6.5 | Building Services | |||
Common area and exterior lighting | 3 | 6 | 9 | |
Elevators | 13 | 9 | 22 | |
Pumps | 6 | 8 | 14 | |
Electrical System | 1 | 5 | 6 | |
6.6 | Indoor Electrical End-Use | |||
Indoor Lighting | 12 | 12 | ||
Comfort Systems | 50 | |||
ENS Score | 70 | 130 | 200 |
Section | Components | Minimum points | Additional points | Maximum points |
---|---|---|---|---|
6.7 | Renewable Energy Systems | |||
Solar Hot Water Systems | 10 | 10 | ||
Solar Photo Voltaic | 10 | 10 | ||
Additional ENS Score | 20 | 20 |
3.2.1 Construction drawings and specifications shall show all pertinent data and features of the building, equipment, and systems in sufficient detail to permit the authority having jurisdiction to verify that the building complies with the requirements of this code.
3.2.2 Details shall include, but are not limited to:
3.3.1 The compliance with the code can be demonstrated using the software/toolkit that has been approved by the BEE or authority having jurisdiction.
4.1.1 All requirements for building envelope under mandatory section as mentioned in Chapter 4 of ENS Part I.
4.2.1 All 3 phase shall maintain the power factor of 0.97 at the point of connection
4.3.1 Residential buildings exceeding the threshold defined under section 2.2 of this code shall monitor the electrical energy use for each of the following separately:
4.3.2 The electrical energy use shall be recorded at an interval of minimum of every 15 minutes and reported at least hourly, daily, monthly and annually. The monitoring equipment should be capable of transmitting the data to the digital control system/ energy monitoring information system. The digital control system shall be capable of maintaining all data collected for a minimum of 36 months.
4.3.3The metering shall display current (in each phase and the neutral), voltage (between phases and between each phase and neutral), and total harmonic distortion (THD) as a percentage of total current in case of transformers
4.4.1 If an Electric Vehicle Charging Infrastructure is installed in the premise, it shall be as per revised guidelines issued by Ministry of Power for Charging Infrastructure for Electric Vehicles on 1st October 2019, or any subsequent amendments.
4.5.1 The power cabling shall be sized so that the distribution losses shall not exceed 3% of the total power usage in the ENS building. Record of design calculation for the losses shall be maintained. Load calculation shall be calculated up to the panel level.
4.5.2Voltage drop for feeders shall not exceed 2% at design load. Voltage drop for branch circuit shall not exceed 3% at design load.
5.1.1 All requirements for building envelope uincluding Openable Window-to-Floor area ratio, Visible Light Transmittance, as mentioned in chapter 4 of ENS Part I.
5.1.2 The Residential Envelope Transmittance Value (RETV) for the building envelope (except roof) for four climate zones, namely, Composite Climate, Hot-Dry Climate, Warm-Humid Climate, and Temperate Climate, shall comply with the maximum RETV of 12 W/m2. Thermal transmittance of building envelope for cold climate shall comply with the maximum U value of 1.3 W/m2·K.
5.1.3 Thermal transmittance of roof shall comply with the maximum Uroof value of 1.2 W/m2·K.
5.2.1 The Lighting power density (LPD) and Luminous efficacy (LE) of permanently installed lighting fixtures in common area of the ENS compliant building shall meet the requirements of either maximum LPD or minimum luminous efficacy given in Table 4.
Common Areas | Maximum LPD (W/m2) | Minimum luminous efficacy (lm/W) |
---|---|---|
Corridor lighting & Stilt Parking | 3.0 | All the permanently installed lighting fixtures shall use lamps with an efficacy of at least 105 lumens per Watt |
Basement Lighting | 1.0 | All the permanently installed lighting fixtures shall use lamps with an efficacy of at least 105 lumens per Watt |
5.2.2 When the exterior lighting load is more than 100 W, the permanently installed lighting fixtures shall use lamps with an efficacy of at least 105 lumens per Watt or meet the maximum LPD requirements given in Table 5.
Exterior Lighting Areas | Maximum LPD (W/m2) |
---|---|
CDriveways and parking (open/ external) | 1.6 |
Pedestrian walkways | 2.0 |
Stairways | 10.0 |
Landscaping | 0.5 |
Outdoor sales area | 9.0 |
5.2.3 Lamps for all exterior applications apart from emergency lighting shall be controlled by photo sensor or astronomical time switch that is capable of automatically turning off the exterior lighting when daylight is available, or the lighting is not required.
5.3.1 The Elevators installed in the ENS compliant building shall meet the following requirements:
5.4.1 Either hydro-pneumatic pumps having minimum mechanical efficiency of 70% or BEE 5 star rated Pumps shall be installed in the ENS building.
5.5.1Power transformers of the proper ratings and design must be selected to satisfy the minimum acceptable efficiency at 50% and full load rating. The permissible loss shall not exceed the values listed in Table 6 for dry type transformers and BEE 5-star rating in Table 7 for oil type transformers.
Rating kVA | Max. Losses at 50% loading W* | Max. Losses at 100% loading W* | Max. Losses at 50% loading W* | Max. Losses at 100% loading W* |
---|---|---|---|---|
Up to 22 kV class | 33 kV class | |||
100 | 940 | 2400 | 1120 | 2400 |
160 | 1290 | 3300 | 1420 | 3300 |
200 | 1500 | 3800 | 1750 | 4000 |
250 | 1700 | 4320 | 1970 | 4600 |
315 | 2000 | 5040 | 2400 | 5400 |
400 | 2380 | 6040 | 2900 | 6800 |
500 | 2800 | 7250 | 3300 | 7800 |
630 | 3340 | 8820 | 3950 | 9200 |
800 | 3880 | 10240 | 4650 | 114000 |
1000 | 4500 | 12000 | 5300 | 12800 |
1250 | 5190 | 13870 | 6250 | 14500 |
1600 | 6320 | 16800 | 7500 | 18000 |
2000 | 7500 | 20000 | 8880 | 21400 |
2500 | 9250 | 24750 | 10750 | 26500 |
*The values as per Indian Standard/BEE Standard & Labeling notification for dry type transformer corresponding to values in this table will supersede as and when the Indian standards/ BEE Standard & Labeling notification are published. |
Rating kVA | Impedance (%) | BEE 1 Star | BEE 3 Star | BEE 5 Star | |||
---|---|---|---|---|---|---|---|
50% Load | 100% Load | 50% Load | 100% Load | 50% Load | 100% Load | ||
16 | 4.5 | 135 | 440 | 108 | 364 | 87 | 301 |
25 | 4.5 | 190 | 635 | 158 | 541 | 128 | 448 |
63 | 4.5 | 340 | 1140 | 270 | 956 | 219 | 791 |
100 | 4.5 | 475 | 1650 | 392 | 1365 | 317 | 1130 |
160 | 4.5 | 670 | 1950 | 513 | 1547 | 416 | 1281 |
200 | 4.5 | 780 | 2300 | 603 | 1911 | 488 | 1582 |
250 | 4.5 | 980 | 2930 | 864 | 2488 | 761 | 2113 |
315 | 4.5 | 1025 | 3100 | 890 | 2440 | 772 | 1920 |
400 | 4.5 | 1225 | 3450 | 1080 | 3214 | 951 | 2994 |
500 | 4.5 | 1510 | 4300 | 1354 | 3909 | 1215 | 3554 |
630 | 4.5 | 1860 | 5300 | 1637 | 4438 | 1441 | 3717 |
1000 | 5.0 | 2790 | 7700 | 2460 | 6364 | 2170 | 5259 |
1250 | 5.0 | 3300 | 9200 | 3142 | 7670 | 2991 | 6394 |
1600 | 6.25 | 4200 | 11800 | 3753 | 10821 | 3353 | 9924 |
2000 | 6.25 | 5050 | 15000 | 4543 | 13254 | 4088 | 11711 |
2500 | 6.25 | 6150 | 18500 | 5660 | 16554 | 5209 | 14813 |
Total loss values given in above table are applicable for thermal classes E, B and F and have component of load loss at reference temperature according to Clause 17 of IS 1180 i.e., average winding temperature rise as given in Column 2 of Table 8.2 plus 300C. An increase of 7% on total for thermal class H is allowed. Permissible total loss values shall not exceed: * 5% of the maximum total loss values mentioned in IS 1180 for oil type transformers in voltage class above 11 kV but not more than 22 kV * 7.5% of the maximum total loss values mentioned in above IS 1180 for oil type transformers in voltage class above 22 kV and up to and including 33 kV |
5.5.2All measurement of losses shall be carried out by using calibrated digital meters of class 0.5 or better accuracy and certified by the manufacturer. All transformers of capacity of 500 kVA and above would be equipped with additional metering class current transformers (CTs) and potential transformers (PTs) additional to requirements of Utilities so that periodic loss monitoring study may be carried out.
Components | Minimum points | Additional points | Maximum points |
---|---|---|---|
Building Envelope Building Envelope |
47 | 40 | 87 |
Building Services | |||
Common area and exterior lighting | 3 | 6 | 9 |
Elevators | 13 | 9 | 22 |
Pumps | 6 | 8 | 14 |
Electrical System | 1 | 5 | 6 |
Indoor Electrical End-Use | |||
Indoor Lighting | 12 | 12 | |
Comfort Systems | 50 | ||
ENS Score | 70 | 130 | 200 |
Renewable Energy Systems Components | Minimum points | Additional points | Maximum points |
---|---|---|---|
Solar Hot Water Systems | 10 | 10 | |
Solar Photo Voltaic | 10 | 10 | |
Additional ENS Score | 20 | 20 |
6.4.1 Thermal transmittance of roof (Uroof).
Maximum Score 7 Points.
Score breakup for the thermal transmittance of roof is as mentioned in the Table 10
Minimum, if opted: Thermal transmittance of roof shall comply with the maximum Uroof value of 1.2 W/m2·K. | Up to 3 Points | |||
Additional: 1 Point for every reduction of 0.23 W/m2·K in thermal transmittance of roof from the Minimum requirement prescribed under §6.1(a). | Up to 4 Points |
6.4.2 Residential Envelope Transmittance Value (RETV) for building envelope
(except roof) for four climate zones, namely, composite climate, Hot-Dry
climate, Warm-Humid climate, and Temperate climate7
Maximum Score 80 Points
Score breakup for the Residential envelope transmittance value for building envelope
(except roof) is as mentioned in the Table 11. Residential Envelope Transmittance
Value (RETV) for building envelope (except roof) for four climate zones, namely,
composite climate, Hot-Dry climate, Warm-Humid climate, and Temperate climate
shall be calculated as specified in ENS Part I.
The RETV for the building envelope (except roof) for four climate zones, namely, Composite Climate, Hot-Dry Climate, Warm-Humid Climate, and Temperate Climate, shall comply with the maximum RETV of 15 W/m² . | 44 Points | |||
For RETV less than 15 and up to 12 W/m² , score will be calculated by following equation:74 – 2 x (RETV) | Up to 50 Points | |||
For RETV less than 12 and up to 6 W/m² , score will be calculated by following equation: 110 – 5 x (RETV) | Up to 80 Points | |||
Additional: For RETV less than 6 W/m² | 80 Points |
6.4.3 Thermal transmittance of building envelope (except roof) for cold climate
(U ENVELOPE, COLD)8
Maximum Score 80 Points
Score breakup for the Thermal transmittance of building envelope (except roof)
for cold climate (U ENVELOPE, COLD ) is as mentioned in the Table 12. Thermal
transmittance of building envelope (except roof) for cold climate (U ENVELOPE, COLD ) shall be calculated as specified in ENS-I.
For Cold Climate Zone, the thermal transmittance of the building envelope (except roof) for cold climate shall comply with the maximum of 1.8 W/m2·K. | 44 Points | |||
For thermal transmittance of building envelope between 1.8 W/m2·K and 1.32 W/m2·K following equation shall be used: 66.5 - 12.5 x (thermal transmittance of building envelope in W/m2·K) | Up to 50 Points | |||
For thermal transmittance of building envelope between 1.32 W/m2·K and 0.36 W/m2·K following equation shall be used: 91.25 – 31.25 x (thermal transmittance of building envelope in W/m2·K) | Up to 80 Points | |||
For thermal transmittance of building envelope less than 0.36 W/m2·K | 80 Points |
6.5.1 Common Area and exterior Lighting
Common Areas | Maximum LPD (W/m2) | Minimum luminous efficacy (lm/W) |
---|---|---|
Corridor lighting & Stilt Parking | 3.0 | All the permanently installed lighting fixtures shall use lamps with an efficacy of at least 105 lumens per Watt |
Basement Lighting | 1.0 | All the permanently installed lighting fixtures shall use lamps with an efficacy of at least 105 lumens per Watt |
Exterior Lighting Areas | Maximum LPD (W/m2) |
---|---|
CDriveways and parking (open/ external) | 1.6 |
Pedestrian walkways | 2.0 |
Stairways | 10.0 |
Landscaping | 0.5 |
Outdoor sales area | 9.0 |
Minimum:
The Lighting power density (LPD) and Luminous efficacy (LE) of permanently installed lighting fixtures in common area of the ENS building shall meet the requirements of either maximum LPD or minimum luminous efficacy given in Table 13, Table 14 and as mentioned in section 6.5.1 (ii) and 6.5.1 (iii) for all the areas/ zones applicable for the building for which compliance is sought. If a particular area/ zone is not applicable to a building for which compliance is sought, the performance requirement of the respective zone/ area is not required. |
3 Points | |||||||||||
Additional: Installing all the permanently installed lighting fixtures with lamp luminous efficacy of 95 lm/W in areas mentioned below
|
Up to 3 Points | |||||||||||
Additional: Lamps for all exterior applications apart from emergency lighting shall be controlled by photo sensor or astronomical time switch that is capable of automatically turning off the exterior lighting when daylight is available, or the lighting is not required. Installing all the permanently installed lighting fixtures in all corridor lighting, stilt parking, basement lighting and exterior lighting with lamp luminous efficacy of 105 lm/W.
|
Up to 6 Points |
6.5.2 Elevators
Maximum Score 22 Points
Score breakup for the elevators is as mentioned in the Table 16
Minimum: Elevators installed in the ENS building shall meet all the following requirements: i. Install high efficacy lamps for lift car lighting having minimum luminous efficacy of 85 lm/W ii. Install automatic switch-off controls for lighting and fan inside the lift car when are not occupied iii. Install minimum class IE 3 high efficiency motors iv. Group automatic operation of two or more elevators coordinated by supervisory control |
13 Points | |||
Additional: Additional points can be obtained by: i. Installing the variable voltage and variable frequency drives. (4 points) ii. Installing regenerative drives. (3 points) iii. Installing class IE4 motors. (2 points) |
9 Points |
6.5.3 Pumps
Maximum Score 14 Points
Score breakup for the thermal transmittance of roof is as mentioned in the Table 17
Minimum: Either hydro-pneumatic pumps having minimum mechanical efficiency of 60% or BEE 4 star rated Pumps shall be installed in the ENS building. |
6 Points | |||
Additional: Additional points can be obtained by: i.Installation of BEE 5 star rated pumps (5 Points) ii. Installation of hydro-pneumatic system for water pumping having minimum mechanical efficiency of 70% (3 Points) |
8 Points |
6.5.4 Electrical Systems
Maximum Score 6 Points
Score breakup for the electrical system is as mentioned in the Table 18
Minimum: Power transformers of the proper ratings and design must be selected to satisfy the minimum acceptable efficiency at 50% and full load rating. The permissible loss shall not exceed the values listed in Table 8 for dry type transformers and BEE 4-star rating in Table 9 for oil type transformers. |
13 Points | |||
Additional: Additional points can be obtained by providing all oil type transformers with BEE 5 star rating. |
5 Points |
The points mentioned under section 6.6 are not mandatory to show overall compliance
6.6.1 Indoor lighting
Maximum Score 12 Points
Score breakup for the electrical system is as mentioned in the Table 19
Minimum, if opted: All the lighting fixtures shall have lamps with luminous efficacy of minimum 85 lm/W installed in all bedrooms, hall and kitchen. |
4 Points | |||
Additional: Additional points for indoor lighting by installing all lighting fixtures in all bedrooms, hall and kitchen shall have lamps luminous efficacy as per following: 95 lm/w (3 Points) 105 lm/W (8 Points). |
upto 8 Points |
6.6.2 Comfort Systems
Maximum Score 50 Points
Score breakup for the comfort System for ceiling fans and Air Conditioners is as
mentioned in the Table 20 and Table 21. If comfort system is applicable, in such case
minimum marks for ceiling fans and air conditioners will be mandatory.
Minimum, if opted: All ceiling fans installed in all the bedrooms and hall in all the dwelling units shall have a service value as given below: For sweep size <1200 mm: equal or greater than 4 m3/minute·Watt For sweep size >1200 mm: equal or greater than 5 m3/minute·Watt BEE Standards and Labeling requirements for ceiling fans shall take precedence over the current minimum requirement, as and when it is notified as mandatory. |
6 Points | |||
Additional: Additional points for ceiling fans by installing in all the bedrooms and hall in all the dwelling units as per following: the dwelling units as per following: 4 Star 5 Star |
1
Points 3 Points |
Minimum, if opted: Unitary Type: 5 Star Split AC: 3 Star VRF: 3.28 EER Chiller: Minimum ECBC Level values as mentioned in ECBC 2017 |
20 Points | |||
Additional: Split AC: 4 Star VRF: Not Applicable as on date, however, whenever BEE Star labelling for VRF is launched, Star 4 will be applicable Chiller: Minimum ECBC+ Level values as mentioned in ECBC 2017 |
9 Points | |||
Additional: Split AC: 5 Star VRF: Not Applicable as on date, however, whenever BEE Star labelling for VRF is launched, Star 5 will be applicable Chiller: Minimum ECBC+ Level values as mentioned in ECBC 2017 |
21 Points |
6.7.1 Solar Water Heating
Solar water heater shall meet the minimum efficiency level
mentioned in IS 13129 Part (1&2) and for evacuated tube collector the storage tanks
shall meet the IS 16542:2016, tubes shall meet IS 16543:2016 and IS 16544:2016 for
the complete system.
Maximum Score 10 Points
Score breakup for the electrical system is as mentioned in the Table 22
Minimum, if opted: The ENS compliant building shall provide a solar water heating system (SWH) of minimum BEE 3 Star label and is capable of meeting 100% of the annual hot water demand of top 4 floors of the residential building. or 100% of the annual hot water demand of top 4 floors of the residential building is met by the system using heat recovery |
5 Points | |||
Additional: Additional points can be obtained by installing SWH system as per as per following: 100% of the annual hot water demand of top 6 floors of the residential building (2 points) 100% of the annual hot water demand of top 8 floors of the residential building (5 points) |
upto 5 Points |
6.7.2 Solar Photo-Voltaic
Maximum Score 10 Points
Score breakup for the electrical system is as mentioned in the Table 23.
Minimum, if opted: The ENS compliant building shall provide a dedicated Renewable Energy Generation Zone (REGZ) – Equivalent to a minimum of 2 kWh/m2.year of electricity; or Equivalent to at least 20% of roof area. The REGZ shall be free of any obstructions within its boundaries and from shadows cast by objects adjacent to the zone.. |
5 Points | |||
Additional: Additional points can be obtained by installing solar photo voltaic as per following: Equivalent to a minimum of 3 kWh/m2.year of electricity or Equivalent to at least 30% of roof area (2 points) Equivalent to a minimum of 4 kWh/m2.year of electricity or Equivalent to at least 40% of roof area (5 points) |
upto 5 Points |
unconditioned spaces. The U-value for an envelope component indicates its ability to reduce heat transfer through conduction. U-value is expressed as W/m2·K.
Rationale: Embodied energy in construction in India (especially in “formal’ residential buildings of the sort
that are covered by the ENS code) can sometimes be of the order of magnitude of many decades
of operating energy use9 and therefore is very significant to consider when such a code is being
developed.
However, this was true for non-air-conditioned housing stock, and it seems likely that, like in the
developed economies, increasing consumption of operating energy (e.g., for appliances, common
area services, air-conditioning etc.) may cause the embodied energy to become less significant
compared to operating energy. Still this is an important area to include in the code.
Embodied energy is also important because much of it is consumed in the form of primary energy
(coal, oil, fuels) causing direct pollution and carbon emissions.
Embodied energy is the sum of all energy used in the construction process, i.e., in the product,
transport and installation: from the extraction of raw materials, manufacture of materials and
fabrication of products, to their transportation and installation in buildings. It is often measured
in megajoules per square meter. But its units can also be kWh(th) (Thermal Kilowatt hours, with
1kWh(th) being equivalent of 3600 kJ) per sqm of built-up-area, making it more easily comparable
with EPI of the ENS code.
Cement and steel are the major contributors of embodied energy in residential building construction
in India. According to the study conducted by Jadavpur University10, 98% of the embodied energy
is attributed to the embodied energy of the materials used and 2% is the contribution of actual
erection of the building. Unfortunately, embodied energy is often “hidden” in industry for the
manufacture and transport of materials, and the transportation of workers.
Institutes of technological research need to be tasked with creating standards for embodied energy
benchmarks based on average and best practice. If necessary this research needs to attract funds
from the building industry and foundations.
Embodied Energy measured in kWh(th)/sqm and Operating Energy measured in kWh(th)/sqm.year
can be combined. In order to combine the (capital) embodied energy with the operating energy, it
is necessary to merge the two to units equivalent of kWh(th)/sqm.year so that a single number can
represent the energy performance of a project.
In a recent piece of research for Technology Information Forecasting and Assessment Council
of India11, it was found that the best way to translate from kWh(th)/sqm (Embodied Energy) to
9 The Mud Village project, sponsored by HUDCO, entry by Studio Plus, 1987
10 Embodied Energy Analysis of Multi-storied Residential Buildings in Urban India, S Bardhan - WIT Transactions on
Ecology and the Environment, 2011
11 Technology Vision 2035, Technology Information Forecasting and Assessment Council (TIFAC) 2014
Embodied Energy
Annex A-Embodied Energy A
Bureau of Energy Efficiency 29 Eco Niwas Samhita 2021
kWh(th)/sqm.year (equivalent Operating Energy) would be to set up a notional or actual discount/
replacement rate of construction taking its nominal life, say, as:
50 years life leading to a 2% replacement rate of stock for mainstream buildings
20 years life leading to a 5% replacement rate of stock for temporary industrial
materials (steel) buildings.
And so, on
According to a study by HUDCO12, affordable housing uses 4257 MJ/sqm of embodied energy and
so at a rated life of 50 years (or 2% replacement rate), this is equivalent of 85 MJ/sqm.year or 23.6
kWh(th)/sqm.year which is substantial for a building without air-conditioning but low for a building
with various mechanical systems using up substantial operating energy.
This can be codified along with other benchmarks in the ENS code after suitable characterisation,
study, analysis of best practices, and benchmarking.
Energy can be consumed in bad practices that may be observed on building sites. This needs to
be stopped but is currently outside the scope of the ENS code. Typical practices include excessive
requirement of movement of fluids (like mixed concrete) or solids (like steel) on site due to bad
layout, improper sizing of pipes to save initial costs but causing greater pumping power due to
friction losses, an over- or under-reliance on assisted manual labour (which may be seen as a form
of renewable energy), and industry having got used to fuel-based services or energy-on-tap (firm
energy) and so unable to convert to renewable energy such as solar photovoltaic systems (due to
their being infirm, not available on-tap). Often machinery is also often designed so as to have very
high starting surge loads, thereby making it impractical to invest in capital-intensive technologies
(renewable) instead of fuel-based technologies, causing emissions and/or pollution. These areas need
to be improved and then can be codified.
Although according to the study conducted by Jadavpur University14 98% of the embodied energy
is attributed to the embodied energy of the materials used and 2% is the contribution of actual
erection of the building, it is important to look at this seemingly trivial 2% for the main reason
that there can be a lot of energy wasted and emissions and pollution created by bad site practices,
and also because better site practices lead to better buildings and saves cost for the builder, thereby
(ultimately) resulting in more affordable construction.
To achieve this:
Layout planning of sites should be made a course in civil engineering and project
managers need to, by mandate, graduate in at least a one-semester course in this
subject.
Civil engineers need to be able to engage with concepts of renewable energy through
manual labour and solar and wind energy systems and they, along with project
managers, need to, by mandate, graduate in at least a one-semester course in this
subject.
Total energy losses due to waste and friction on site (per unit area of building being
made) need to be analysed, benchmarked, and codified.
All these point to research directions that need to be undertaken (again by Civil
Engineering departments in our Engineering Institutes).
Best industry standards for ratios of running energy: starting surge, need to be
analysed, benchmarked, and codified, so that infirm energy sources such as solar
photovoltaics may be able to be considered to meet the demand of energy on site. It
may be noted that infirm energy sources such as solar photovoltaics could be seen to
be a form of production of energy, and if managed well and with sufficient open area,
with a good rental market created for solar photovoltaics or wind turbines, sites can in
the future become energy-neutral for construction of buildings.
Since research in this area is nascent, it has been kept out of the ENS code for now.
Retrofitting consists of additions and alterations to existing (and, in the context of the ENS code,
residential) building stock and typically this is set into motion by building owners.
For reasons of poor research and difficult practice, this code is currently silent on retrofit provisions
and this appendix is created because given the right conditions this situation may change. This code
does not mention provisions for retrofit cases because of the principle that laws (and codes) should
preferably not be applied retroactively (so we cannot declare a building not meeting standards before
the standard was even made), but in doing so we lose out a large potential of building stock (say over
50% of the residential building stock in 2030 if we read the McKenzie report15 that “nearly 70% of
building stock that will be there in 2030 is yet to be built in India” and geometrically extrapolate it
from 2010 when it was written to 2019 today).
The following market innovations need to be encouraged to cover a large part of India’s existing
residential building stock even when they are not being added to or being altered:
For apartment dwellers, before enforcing this code, there need to be financial (lowinterest
loan) instruments available or created whereby collective retrofitting may take
place through collective action, for example changing of window or wall specifications
through RWA action to comply with provisions of the ENS so that capital cost of
such retrofits may be kept low per month.
For individual house owners, there need to be encouragement of vendors who can
audit and retrofit because until that is done the implementation of ENS code shall be
resisted or “loopholed” by homeowners.
For rental stock, these audit and retrofit companies can undertake audit and retrofit
to meet the ENS code provisions either through RWA or through apartment owners’
associations (this is more difficult but can be eased by easy upgrade costs accompanied
by strict compliance demands).
It would help a lot if the improvements effected by RWAs or contractors can be documented in
a standardized way and the improvements in performance recorded numerically on a plaque or
certificate for the owners to take pride in retrofitting their homes. This can be designed like the BEE
star labels for various appliances.
It is anticipated that since the primary means of enforcing the ENS code is at the time of municipal
approval and completion, this code could be immediately applied (subject to state-by-state
acceptance into law) at the time of application for addition and alterations of buildings.
This would automatically exempt minor addition and alterations (such as raising internal walls,
painting, etc.) For reference, these “minor” retrofits in existing buildings that do not need any
permission according to Delhi Development Authority (DDA), similar to changes in buildings all
over the country, are provided below:
Excerpt from DDA16
1. To convert existing barsati into room provided the wall is made of only 115 mm
thick.
2. Grills and glazing in verandah with proper fixing arrangement.
3. Raising height of front and rear courtyard wall upto 7’ height by putting up jali/
fencing.
4. Providing door in courtyard wherever not provided.
5. Providing sunshades on doors and windows wherever not provided with proper
fixing arrangements.
6. Closing the door.
7. If the bathroom or WC are not having roof, these may be treated as open urinals
and allowed.
8. Raising the wall of balcony/terrace parapet with grill or glazing upto 5’ height.
9. Construction of open staircase (cat ladder) where no staircase has been provided
for approach to the terrace.
10. To put provide additional PVC water tank at ground floor area without disturbing
the common passage.
11. To provide an additional PVC water tank in the scooter/car garage at the surface
level.
12.. To provide loft /shelf in the rooms without chase in the walls.
13. To change the flooring with water proofing treatment.
14. To remove half (41/2) brick wall.
15. To make a ramp at front gate without disturbing the common passage /storm
water drain.
16. To provide sunshades or the outer windows upto 2’wide projection.
17. To provide false ceiling in rooms.
18. To make an opening of maximum size of 2’6” x1’9” for exhaust fan or airconditioner
in existing walls.
19. Fixing of door in back and front courtyard.
20. Converting of window into Almirah subject to availability of light and ventilation
as per building byelaws provided that no structural elements are disturbed and
there is no projection extending beyond the external wall.
21. Shifting of water storage tank/raising of parapet wall upto 5’ height and putting
additional water storage tank. Wherever the existing water storage tank capacity
is less than 500 ltrs in a flat, a 500 ltrs tank can either replace the existing water
storage tank or if possible the additional tank can be added so as to make the
total storage capacity upto 550 ltrs. However, such replacement/provision of
additional tank will be done only on the locations specified for such tanks and
the supporting beams will be required to be strengthened suitably. Parapet wall
around terrace can be increased to a height of 5’.
22. To shift the front glazing, rooms/windows upto existing chajja.
Not implementing retrofit cases for, say, 5 years, it can then be suggested that the ENS code could
be made applicable to all Addition and Alterations cases that come for approval to ULBs. This will
cover at least some 5% of existing building stock (say 10% of 50%) and simultaneously measures (1)
through (3) in the last page need to be actively pursued in the market to make alterations proactively
possible for existing building stock, even when not undertaking additions and alterations.
Generally, alterations in themselves do not require municipal approval. The key changes that require
getting municipal approval is increase of height / FAR / Ground Coverage, all of these are related
to increasing the size of the home.
Studying codes from other countries17, it can be seen that whenever a project comes up for municipal
sanction, the codes require the renovated project to comply with the code provisions. This should be
recommended in India also.
This will leave out only that part of the existing building stock that has a completion certificate
from the ULB and remains unchanged. In time it shall be added to (requiring ULB approval)
or demolished and rebuilt (requiring ULB approval). Therefore, by the later part of this century
definitely the entire residential building stock shall become ENS compliant, even if market forces do
not already make it so.
Residential buildings sector accounts for 24% of the electricity consumption and is the second
largest consumer after industries. Within the building sector, the residential electricity consumption
amounts to 259 TWh. Within this sector, with increasing affluence in the Indian middle class, there is
a tendency (in warm humid, hot dry, composite and even moderate climates which always have some
hot days) to create comfort by installing an air-conditioner or two. Capital costs of air conditioning is
low compared to capital costs of building (today, cheap – and inefficient – air-conditioning can be as
low as 5% of the building cost). EMI-based loans make it easy for even a lower middle-class family
to install split air-conditioners at less than the monthly energy costs of running the same.
Use of air-conditioning therefore is a major hurdle in creating energy efficient residential stock in
India, since it cannot be denied that it creates superior comfort in all sorts of conditions: warm
humid, hot dry, composite, and moderate.
Often the rationale for a lower middle-class family, who realize that the energy bills are not easy to
manage, is that they will use it minimally, only in the night and only in extreme weather, or by setting
the thermostat up to higher temperatures. However, air-conditioning, with its superior performance
in terms of managing humidity, is addictive, and there is a tendency for its use to increase to the limit
of the users’ paying capacity, and even beyond it.
It is worse that in this economic class, the tendency is to procure cheap, lower rated inefficient
equipment, and install it in poorly insulated houses, which uses even more electricity than it could.
This causes residential air-conditioning to become a major barrier in energy efficiency (USAID,
2014)18. This issue is a major guzzler of energy in houses and needs to be mitigated by codification.
However, since the research on this is ongoing, this has not yet been included in the ENS code.
On November 15, 2019, the Rocky Mountain Institute (RMI) in collaboration with the Ministry of
Housing and Urban Affairs (MoHUA) of the Government of India (GoI) announced the results
of a Global Cooling Prize competition, for Incentivizing the development of a residential cooling
solution that will have at least five times less climate impact than standard residential/room air
conditioners (RAC) units in the market today. This technology could prevent up to 100 gigatons
(GT) of CO2-equivalent emissions by 2050, and put the world on a pathway to mitigate up to 0.5˚C
of global warming by 2100, all while enhancing living standards for people in developing countries
around the globe
Therefore, the following are urgently required to be researched and implemented for Indian
residences to become comfortable while remaining energy efficient, at capital costs that are
affordable or can be made affordable by fiscal incentives or financial instruments:
Natural and SENS Score Ventilation
If buildings can achieve comfort by natural or sENS Score ventilation, this would entirely avoid the
use of energy for mechanical cooling, and needs to be highly encouraged.
Natural ventilation fulfils two primary needs: first, it gives fresh air for satisfactory indoor quality;
and, second when the outdoor temperature are comfortable (during night and transition seasons), it
expels heat from inside the structure and facilitates cooling.
Natural ventilation is of course not useful for cooling when the outdoor air is at a temperature
higher than the set-point or desired indoor temperatures. This leads us to another very important
concept of ventilation, sENS Score ventilation, opening the building very much to the outdoor air
whenever the temperature outside is more comfortable than the inside, namely summer nights and
winter days.
The National Building Code 2016 (Part 8; 1; 5. Ventilation) or ASHRAE 62.1–2016 provide
standard ventilation rates for acceptable indoor quality.
To aid cooling a larger volume of airflow is required than the standard ventilation rates.
The rate of ventilation by natural means through windows or other openings depends on,
a) direction and velocity of wind outside and sizes and disposition of openings (wind
action); and
b) convection effects arising from temperature of vapour pressure difference (or both)
between inside and outside the room and the difference of height between the outlet
and inlet openings (stack effect).
One of the parameters to quantify the adequacy of natural ventilation is hourly air change rate
(ACH), which is a proportion of how frequently the air volume inside a room is supplanted by outside air in 60 minutes. The larger the number, the better is the cooling potential through common
ventilation. As a rule, 5 to 20 ACH gives good natural ventilation.
NBC 2016 discusses the design guidelines for natural ventilation in the 5.4.3 of Part 8: Building
Services of the code.
Once the promotion of naturally ventilated buildings can be successfully undertaken, it should be
possible to eliminate the use of air-conditioning or at least drastically reduce its use in all but the
most affluent residences.
Ventilation in residential buildings can be provided by one of the following methods:
a) Natural supply and natural exhaust of air (natural ventilation)
b) Natural supply and mechanical exhaust of air (mechanical ventilation, see below)
c) Mechanical supply and natural exhaust of air (mechanical ventilation, see below)
d) Mechanical supply and mechanical exhaust of air (mechanical ventilation, see below).
Mechanical Ventilation
There are a range of circumstances in which natural ventilation may not be possible or sufficient to
attain thermal comfort:
Kitchen Ventilation
Kitchen is always the hottest space in a flat on account of the huge amount of heat produced due to
cooking. The arrangement of a decent ventilation framework that can proficiently separate hot air from the kitchen before it blends with the encompassing air can help lessen the heat in the kitchen
and adjoining spaces.
For powerful natural ventilation of the kitchen, notwithstanding the window, an extra louvre opening
ought to be given to further aid the movement of air.
If the kitchen is ventilated utilizing a fume hood, the distance of the hood from the gas fire and the
fume flow rate should be appropriately chosen for best ventilation of the kitchen.
Evaporative Cooling
Evaporative cooling is a process that uses the effect of evaporation of water as a natural heat sink.
The amount of sensible heat absorbed depends on the amount of water that can be evaporated.
Currently this is the most promising area of reducing energy for cooling, except that it is largely
ineffective in warm and humid seasons or climates. Sensible heat from the air is absorbed to be used
as latent heat necessary to evaporate water.
EPI for Evaporative Cooler
The efficiency of the evaporative coolers is measured based on the evaporative efficiency which
depends on the outside dry bulb temperature and relative humidity of the airstream.
The EPI shall be estimated for Evaporative Coolers as shown below:
EPI = [Total Wattage of fan(s) + Total wattage of pump(s)]
* Hours of operation/ (1000 * Built-up area)
Rationale for EPI calculation for evaporative cooler
Parameters influencing EPI for evaporative cooler are:
Design Parameters
District Cooling
District cooling systems, which typically require about 15% less capacity than conventional
distributed cooling systems for the same cooling loads due to load diversity and flexibility in capacity
design and installation. District cooling helps in greatly reducing the peak demands and provide new
generation capacity to meet cooling demand. District cooling systems are appropriate for densely
populated urban areas having mixed uses of buildings with high cooling requirement. It provides
enhanced level of reliability and flexibility, as individual building’s cooling demand can increase or
decrease without the need to change the main plant’s capacity.
District cooling indicates central manufacturing and distribution of cooling energy. Chilled water is
generated at main plant and then by means of an underground insulated pipeline is provided to the
buildings to cool down the interior within a neighbourhood/zone. Specifically, designed devices (HX
& pumps, AHUs etc.) in each building utilize this chilled water to decrease the temperature level of
air going through the building’s cooling system.
Thermal Energy Storage
Thermal storage may be used for limiting maximum demand, by controlling peak electricity load
through reduction of chiller capacity, and by taking advantage of high system efficiency during low
ambient conditions. Thermal storage would also help in reducing operating cost by using differential
time-of-the day power tariff, where applicable.
The storage media can be ice or water. Water need stratified storage tanks and is mostly viable with
large storage capacity and has an advantage of plant operation at higher efficiencies but requires
larger storage volumes. In case of central plant, designed with thermal energy storage, its location
shall be decided in consultation with the air conditioning engineer. For roof top installations,
structural provision shall take into account load coming on the building/structure due to the same.
For open area surface installation, horizontal or vertical system options shall be considered and
approach ladders for manholes provided. Buried installation shall take into account loads due to
movement of vehicles above the area.
The concept of smart home is in existence for many decades; however, it has gained further
importance in present scenario due to increase in demand for comfort and convenience (with
growth of disposal income), increased dependence on appliances, increase in per capita electricity
consumption and availability of rooftop solar PV and EV for potential onsite generation and storage
respectively.
Alongside these drivers at consumer end; technology advancement in the form of availability of
high speed computing devices (smart phones) and affordable internet data, reduction in size of
IoT devices / sensors and by shifting sophisticated computing functions to cloud and development
of complex algorithms to control systems as per user requirement and preference (using Artificial
Intelligence) has provided fresh push to demand of smart home product and services.
The need of utility-based demand response program to match the variable consumer demand (due
to use of diverse appliances) with dynamic electricity supply (due to penetration of renewable energy
in grid) is gradually making the smart home solutions a must have product/service in every home, to
make it demand response ready.
To manage the energy use in a home in order to make optimum use of these opportunities and
for minimizing the demand supply gap, there is need of Smart Home Energy Management System
(SHEMS). SHEMS can be defined20 as the combination of a service and devices that are designed
to work together to deliver occupancy-based optimization of energy use. SHEMS21 consist of
hardware and software, which are linked and integrated to, monitor energy usage, provide feedback
on energy consumption, enhance control and provide remote access and automation provisions
over appliances and devices that use energy in the home. SHEMS can deliver a range of services and
benefits to households, which includes: