About ECO-NIWAS 2021

1. Introduction

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.

  1. Annex A: Annualized embodied energy
    Annex B: Better construction practices
    Annex C: Retrofitting of residential buildings
    Annex D: Improved air cooling
    Annex E: Smart Home

Scope

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 –

  1. 2.2.1 Residential buildings built on a plot area5 of ≥ 500 m2
  2. 2.2.2 Residential part of Mixed land-use building projects6, built on a plot area of ≥ 500 m2.

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:

  1. 2.9.1 Any policy notified as taking precedence over this Code, or any other rules on safety, security, health, or environment by Central, State, or Local Government.
  2. 2.9.2 BEE’s Standards and Labelling for appliances and Star Rating Program for buildings, or any reference standard prescribed by the Code, provided both or either are more stringent than the requirements of this Code.

CODE COMPLIANCE

3.1 Compliance Approaches

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

  1. a) Prescriptive approach as mentioned in Chapter 5
  2. b) Points based system approach as mentioned in Chapter 6

3.1.2 Table 1 below gives the minimum ENS score required to be obtained as per eligible project category:

Table 1 Minimum ENS Score Requirement
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

    1. If a part of the mixed-use building classification (residential or commercial) is less than 10% of the total above grade floor area, the mixed-use building part shall show compliance based on the building sub-classification having higher percentage of above grade floor area.
    2. If a part of the mixed-use building has different classification (residential or commercial) and one or more sub-classification is more than 10% of the total above grade floor area, the compliance requirements for each sub-classification, Code Compliance Code Compliance 3 Bureau of Energy Efficiency 6 Eco Niwas Samhita 2021 having area more than 10% of above grade floor area of a mixed-use building, shall be determined by the requirements for the respective building classification.
    3. Basement and common area services, designed for a particular building use or documented with respective buildings for compliance with authority having jurisdiction, needs to show compliance with the clauses for the respective building requirement.
    1. Compliance for site marked for affordable housing, as per the applicable bye law, shall be shown separately.
    2. The overall point to be achieved for ENS building for site marked for affordable housing is 70.
    3. If the site area with low rise buildings in the overall project is more than or equal to 20% of the total site area, the site marked for low rise building, as per the applicable bye law, shall be shown separately to other residential building type. The overall point to be achieved for ENS building for the site marked for this low-rise building is 47.
    4. If the site area with low rise buildings in the overall project is less than 20% of the total site area, the site marked for low rise building, as per the applicable bye laws, shall be shown together with other residential building category. The overall point to be achieved for ENS Compliance for the overall site is 100. In such projects:
      1. Mandatory points – compliance to be shown only for the components which are provided in the project and is necessary as per the applicable building bye law.
      2. Additional points –
        1. to claim the additional points of any component in building services and indoor area services mentioned in section 6.5 and 6.6, except for requirements for basement lighting, project needs to install the component for minimum 80% of the total above grade area (AGA) or for component designed for 80% of total AGA.
        2. to claim the additional points for requirements of basement lighting mentioned in section 6.5, ENS building to show compliance for total basement area designed in the project and as per applicable building by-law.
        3. to claim the additional points of any component in building envelope mentioned in section 6.4, project needs to install the component as mention in section of the component for overall project.

3.1.7 Prescriptive Method

  1. In order to demonstrate compliance with the code through the Prescriptive Method, the ENS building shall meet mandatory requirements specified under chapter 4 and all prescriptive requirements as per chapter 5, for compliance purpose.

3.1.8 Point System Method

  1. In order to demonstrate compliance with the code through the Point System Method, the ENS building shall meet all applicable mandatory requirements specified in chapter 4 and obtain a minimum ENS Score as per section 6.1 in chapter 6, for this purpose:
    • All Low-rise residential buildings must obtain minimum 47 points from ‘Building Envelope’ under section 6.4.
    • All Affordable housing scheme must obtain minimum 70 points from ‘Building Envelope’, and ‘Building Services’ under section 6.4 and 6.5 respectively.
    • All High-rise residential buildings must obtain minimum 100 points from ‘Building Envelope’ and ‘Building Services’, ‘Indoor Electric End-Use’ and ‘Renewable Energy Systems’ under section 6.4, 6.5, 6.6 and 6.7, respectively.
    • The Table 2 below gives the component wise distribution of points for each building component to achieve minimum ENS Score.
    Table 2 Component wise Distribution of ENS Score
    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
  2. The code also provides additional 20 points for renewable energy as mentioned in Table 3 which can be availed after fulfilling the minimum points criteria as per Table 3.
    Table 3 Score for Renewable Energy System Components
    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. In order to demonstrate compliance with the code using Point System Method, the ENS building must obtain the applicable minimum points as specified under section Code Compliance Bureau of Energy Efficiency 8 Eco Niwas Samhita 2021 6.1 and get remaining points by:
    1. meeting the requirements labelled as ‘additional points’ of building envelope under section 6.4; and/or
    2. meeting the requirements labelled as ‘additional’ of ‘Building Services’ & Indoor Electric End-Use under section 6.5 & 6.6; and/or
    3. meeting the requirements labelled as ‘additional’ of ‘Renewable Energy Systems’ under section 6.7.
  4. The mandatory points or additional points shall be assigned as per the least energy efficient specification of all the products installed under a category in the building, unless the trade off or weighted average is allowed for the particular category.
  5. In a mixed mode building category, energy efficiency measure applied in the common services and installed at a overall site level shall meet the most stringent specification requirement among the mentioned requirements in different categories of building to claim the mandatory and additional points.
  6. To claim the points under the Renewable Energy Systems section, the renewable energy system can be installed collectively at the site level or installed collectively at one or more roofs as per the total renewable energy installation requirement.

3.2 Documentation

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:

  1. Building envelope: opaque construction materials and their thermal properties including thermal conductivity, specific heat, density along with thickness; fenestration U-factors, solar heat gain coefficients (SHGC), visible light transmittance (VLT); overhangs and side fins and operable window area;
  2. Building services: Common area lighting (lamp efficacy for lamps and their controls); pump efficiencies; elevator technologies and their controls; transformer losses; power distribution losses; power factor correction devices; basement ventilation controls; efficiency of charging infrastructure and electric check metering and monitoring system;
  3. Indoor electrical end-use: Indoor lighting (type, number, and wattage of lamps and ballasts; automatic lighting shutoff, occupancy sensors, and other lighting controls); ceiling fans star labelling; service hot water type and their efficiency; airconditioners (system and equipment types, sizes, efficiencies, and controls);
  4. Renewable energy systems: system peak generation capacity, solar water heating system; technical specifications, renewable energy zone area.

3.3 Compliance Tool

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.

Mandatory Requirements

4.1 Building Envelope

4.1.1 All requirements for building envelope under mandatory section as mentioned in Chapter 4 of ENS Part I.

4.2 Power Factor Correction

4.2.1 All 3 phase shall maintain the power factor of 0.97 at the point of connection

4.3 Energy Monitoring

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:

  1. Total electrical energy
  2. Electricity consumption of following applicable end-use:
    1. Common area lighting (Outdoor lighting, corridor lighting, basement lighting)
    2. Elevators
    3. Water pumps
    4. Basement car parking ventilation system
    5. Electricity generated from power back-up
    6. Electricity generated through renewable energy systems
    7. Lift pressurization system

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 Electric Vehicle Charging System

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 Electrical Systems

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.

Prescriptive Requirements

5.1 Building Envelope

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 Common Area and Exterior Lighting

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.

Table 4 Common Area Lighting Requirements
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.

Table 5 Outdoor Lighting Requirement
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 Elevators, if applicable

5.3.1 The Elevators installed in the ENS compliant building shall meet the following requirements:

  1. Install high efficacy lamps for lift car lighting having minimum luminous efficacy of 85 lm/W
  2. Install automatic switch-off controls for lighting and fan inside the lift car when are not occupied
  3. Install minimum class IE 4 high efficiency motors
  4. Installing the variable voltage and variable frequency drives
  5. Installing regenerative drives.
  6. Group automatic operation of two or more elevators coordinated by supervisory control

5.4 Pumps, if applicable

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 Electrical Systems, if applicable

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.

Table 6 Permissible Limit for Dry 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.
Table 7 Permissible Limit for Oil Type Transformers
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.

Point System Method

6.1 The Table 8 below gives the component wise distribution of points for each building component to achieve minimum ENS Score.

Table 8 Component wise Distribution of ENS Score
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

6.2 The code also provides additional 20 points for renewable energy as mentioned in Table 9 which can be availed after fulfilling the minimum points criteria as per section 6.7

Table 9 Score for Renewable Energy System Components
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

6.3 In order to demonstrate compliance with the code using Point System Method, the ENS building must obtain the applicable minimum points as specified under section Code Compliance Bureau of Energy Efficiency 8 Eco Niwas Samhita 2021 6.1 and get remaining points by:

  1. meeting the requirements labelled as ‘additional points’ of building envelope under section 6.4; and/or
  2. meeting the requirements labelled as ‘additional’ of ‘Building Services’ & Indoor Electric End-Use under section 6.5 & 6.6; and/or
  3. meeting the requirements labelled as ‘additional’ of ‘Renewable Energy Systems’ under section 6.7.

6.4 Building Envelope (Maximum 87 Points)

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

Table 10 Points for Thermal Transmittance of Roof (Uroof)
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.

Table 11 Points for 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
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.

Table 12 Points for Thermal transmittance of building envelope (except roof) for cold climate (U ENVELOPE, COLD )
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 Building Services

6.5.1 Common Area and exterior Lighting

  1. 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 LE given in Table 13.
  2. Table 13 Common Area Lighting Requirements
    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
  3. When the exterior lighting load is more than 100 W, the permanently installed lighting fixtures shall use lamps with an efficacy of at least 85 lumens per Watt or meet the maximum LPD requirements given in Table 14.
  4. Table 14 Outdoor Lighting Requirement
    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. 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. Maximum Score 9 Points Score breakup for the Common Area and exterior Lighting is as mentioned in the Table 15
  6. Table 15 Score breakup for the Common Area and exterior Lighting
    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
    Area/ Zones Points
    Corridor lighting and stilt parking 1
    Basement Lighting 1
    Exterior Lighting Areas 1
    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.
    Area/ Zones Points
    Corridor lighting and stilt parking 2
    Basement Lighting 2
    Exterior Lighting Areas 2
    Up to 6 Points

    6.5.2 Elevators
    Maximum Score 22 Points Score breakup for the elevators is as mentioned in the Table 16

    Table 16 Points for Elevators
    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

    Table 17 Points for Pumps
    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

    Table 18 Points for Electrical System
    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

    6.6 Indoor Electrical End-Use

    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

    Table 19 Points for Indoor Lighting
    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.

    1. Ceiling Fans: Points for ceiling fans will be only applicable and could be achieved if all the bedrooms and hall in all the dwelling units are having ceiling fans and points could be gained, if installed as per Table 20.
    2. Table 20 Points for Ceiling Fans
      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
    3. Air Conditioners: Points for air conditioners will be only applicable and could be achieved if all the bedrooms in all the dwelling units are having air conditioners (either unitary, split, VRF or centralized plant) and points could be gained, if installed as per Table 21. In case, air conditioners installed are of mixed type, in that case calculation of points will be based on following formula:
    Table 21 Points for Air Conditioners
    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 Renewable Energy Systems

    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

    Table 22: Points for Solar Water Heating
    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.

    Table 23 Points for Solar Photo Voltaic
    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

ANNEXURES

Annex A-Embodied Energy

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.

Annex B-Best Construction Practice

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.

Annex C- Retrofitting of Residential Buildings

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.


ANNEXURE D Improved Air Cooling

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:


  1. Air-conditioning systems that can be used at higher set-point temperatures (say, up to 28 °C) in combination with ceiling fans. These require higher cfm of air to be pushed through (rather than the industry standard of 400 cfm per Ton) and a balance between refrigerant temperature, air flow, and set point since currently air-conditioning industry has optimised all systems for 22°C - 24°C. As the set point temperature is increased, the other parameters need to change. This kind of device will be ideal for billconscious lower middle classes even if they can progressively afford air-conditioning capex.
  2. Fiscal incentives or financial instruments to lower capex for improving house thermal performance to ENS code levels so that optimum (not too much) air-conditioning is installed. Unfortunately, at this point, the ENS code has been developed assuming that the cooling system is some form of air-conditioning.
  3. Rapid development and deployment of effective an acceptable intermediate technologies including adiabatic technologies, such as passive hybrid and active evaporative coolers, better natural ventilation, indirect evaporative coolers, or chilled coil indirect evaporative coolers, combined with fiscal incentives or financial instruments to lower capex for improving houses to a level so that sufficient passive cooling is managed and the number of days of usage of cooling or conditioning can be brought down.
  4. Alternative desiccant and evaporative systems for cooling (which are not yet welldeveloped). This may require fundamental research and cannot be expected to be rapidly deployed.
Promotion of all these above alternatives through some cultural or social incentives (such as the BEE star rating system or TV promotions) so that they are not perceived as inferior to “complete” air-conditioning. This requires a major social change in attitude from progress seen as consumption only to progress seen as sufficiency, but is probably the most effective instrument for meeting and even bettering the EPI targets of the ENS code.

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:


  1. The building is too deep to ventilate from the perimeter.
  2. Local air quality is poor, for example if a building is next to a busy road.
  3. Local noise levels mean that windows cannot be opened.
  4. The local urban structure is very dense and shelters the building from the wind.
  5. Privacy or security requirements prevent windows from being opened.
  6. Internal partitions block air paths.
  7. The density of occupation, equipment, lighting and so on creates very high heat loads or high levels of contaminants.
Some of these issues can be avoided or mitigated by careful design, and mixed mode or assisted ventilation might be possible, where natural ventilation is supplemented by mechanical systems. Naturally it is not desirable to go with mechanical ventilation where natural ventilation could achieve the similar results.


Where mechanical ventilation is necessary it can be:


  1. A circulation system such as a ceiling fan, which creates internal air movement, but does not introduce fresh air.
  2. A pressure system, in which fresh outside air is blown into the building by inlet fans, creating a higher internal pressure than the outside air.
  3. A vacuum system, in which stale internal air is extracted from the building by an exhaust fan, creating lower pressure inside the building than the outside air. A balanced system that uses both inlet and extract fans, maintaining the internal air pressure at a similar level to the outside air and so reducing air infiltration and draughts.
  4. A local exhaust system that extracts local sources of heat or contaminants at their source, such as cooker hoods, fume cupboards and so on.

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.


  1. Direct Evaporative cooling (DEC): In this system, commonly used in the form of a ‘desert’ cooler, the outdoor air is brought into direct contact with water, cooling the air by converting sensible heat to latent heat. DEC systems could be divided into: Active DECs which are electrically powered to operate and Passive DECs that are naturally operated systems with zero power consumption. In DEC, the water content of the cooled air increases because air is in contact with the evaporated water. This strategy is useful in dry and hot climates.
  2. Indirect Evaporative Cooling: Indirect evaporative coolers operate by decreasing air sensible heat without changing its humidity, which is a distinct advantage over DEC systems (the final temperature approached can be dew point instead of wet bulb temperatures). In indirect evaporative cooling, evaporation occurs inside a heat exchanger and the absolute humidity of the cooled air remains unchanged. This strategy is even more effective in hot and dry climates that DEC and fairly effective for warm and humid climates, too.

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

  1. Location (Climate)
  2. Air delivery rate
  3. Pump water circulation rate
  4. Fan and Pump efficiencies
Technology Parameter


  1. Direct evaporative cooling
  2. Fan and pump motor types



Controls


Dew point based shut-off controller


The EPI ranges from User inputs in calculating the EPI shall include: Power rating of the fan motor (From nameplate) in watts


Power rating of the pump motor (From nameplate) in watts


If a residence uses DEC or IEC or any of the natural, ENS Score, or mechanical ventilation strategies for cooling and avoids Carnot cycle based air-conditioning altogether, then it is proposed that it should automatically be able to meet the ENS code without undergoing the rigorous process of showing complete EPI calculation processes. This part has not been codified but remains in this appendix as a proposal that may be considered.

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.

ANNEXURE E Smart Home

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:


  1. Energy management (energy efficiency)
  2. Demand response (contribute to regulating energy demand)
  3. Electricity generation, storage and delivery to the grid
  4. Comfort and convenience



The functionality of SHEMS can be broadly categorized in five areas that include monitoring, control, user interface, data sharing and grid connectivity.


In smart home, energy and cost savings is achieved by:


  1. Preventing idle running of energy consuming system
  2. Optimization of adjustable building envelope elements to minimize energy demand
  3. Optimization of operating parameters to match user preference
  4. Shifting the operation of non-essential energy consuming systems to off peak time
  5. Making use of renewable energy generation source, whenever available to meet the energy demand
  6. Optimization of charging and discharging of storage for cost saving
Smart home have significant potential for saving energy, however, the net energy savings depends on a range of factors, which include:


  1. The rationale behind automation (comfort or energy saving)
  2. Level and type of automation used (i.e. occupancy based on/off control or fine tuning of operating parameters based on user preference and weather conditions)
  3. User behaviour (whether the user just looks at energy monitoring information or uses this information to change settings or change behaviour)
  4. Power consumption by monitoring and control devices
  5. Additional power consumption by appliances in standby mode due to inclusion of smart communication features.
Several studies have been undertaken at international level by various public and private agencies, including manufacturer associations, to estimate the energy savings from smart home solutions (product and services). Based on one of them, conducted by the Connected Device Alliance (CDA)23, energy savings potential in a dwelling enabled with smart home devices and services could be in the range of 20-30% of the present household energy use, subject to the factors mentioned above.


As technologies are optimised, developed and linked with the implementation of further energy efficiency opportunities in homes, the energy savings potential may increase. Smart Home requirement can be added to code along with other benchmarks in the ENS code after suitable characterisation, study, analysis of best practices, and benchmarking.