High Performance Commercial Buildings in India: Adopting Low-cost Alternative Passive Strategies for Energy Saving

Case Study

General Information:

Client: ITC Green centre
City: Gurgaon
Climate: Composite
Operational schedule – 10 hours, 5 working days in a week
Area of the building: 15,799m² (out of which 9294 m² - conditioned area, 6505 m² - non-conditioned area)

Green Building Design Features:

Building Design

Orientation

‘L’ shape design with main entrance towards north
Longer axes along NE and NW directions
By ‘L’ shape configuration, the width of the floor Plate is reduced for the same amount of floor plate area thereby allowing natural light to penetrate deep into the interior spaces.
It ensures that part of the façade is always shaded

Walls
Walls of air-conditioned zones in all blocks – 230mm AAC block with 70mm stone cladding and 12.5 mm plaster inside

Roof 120mm RCC roof with 76mm ISO board on interior side

Windows

Double glazing window (6-12-6)
Glass on north orientation has a lighter light transmission
The glazing for the building has been designed to maximize the effect of natural light, largely eliminating the need for artificial light during day time.
The high performance window glass, while allowing light inside, does not allow heat and also keeps office cool from inside during the day decreasing the load on HVAC systems
Higher light Transmission Glass on North orientation for better day light integration
Optimum WWR which is less than ECBC standard (40%) helps in reducing external solar heat gain

Building Lighting

Lighting system

Luminaires used – mostly CFLs and T5 lamps in mirror optic fixtures, 36W fluorescent lamps and magnetic ballasts are used in storages, electrical and mechanical rooms
LPD – 7.2W/m2
The LPD (7.2W/m2) is less than the max allowed LPD of ECBC (10.8W/m2) which is very good
According to Energy Star, CFLs provide the same amount of light as an ordinary bulb using 75% less energy
T5 lights have higher efficiency and system miniaturization with daylight life about 18000 hours as compared to 8000 hours of standard fluorescent lamps
Good natural light available in office spaces

Daylight Controls

Switch off daylight sensors with Philips make (model no. LRI 1430/00 ENEC)
Daylight controls switch off lights when daylight is sufficient, reducing the energy consumption of the building

HVAC System Design

Central AC system with 3 screw chillers of 815 TR capacity
COP of the ITC Green Centre: 6.1
ECBC recommended: 5.4
Rated Sq.mt/TR: 18

Energy performance of the building

Lighting Energy Performance of the Building

Annual Consumption (lighting) – 121301 KWh
Lighting Performance Index – 13 KWh/Sqmt/annum

Space Conditioning Energy Performance of the Building

Annual Consumption (A/C) – 596829 KWh
HVAC Performance Index – 64 KWh/Sqmt/annum

Annual energy consumption due to lighting & air conditioning (kWh): 871535

Overall Energy Performance Index due to lighting & air conditioning (kWh/m2): 55

Energy Saving Potential

Comparison of various parameters for ECBC compliant Composite case (ITC Green centre, Gurgaon) with conventional case

Parameters	ECBC compliant case (Existing Building) features	Conventional case
Building design	Building longer axes along NE-NW directions	Building orientation: longer facades facing East-West
Building design	Windows are shaded while roof is not shaded	No roof and wall shading
Building Envelope	No insulation on wall and roof U value for Wall - 0.687 W/m2/K U Value for Roof - 0.335 W/m2/K	No insulation on wall and roof U value for Wall - 2.7 W/m2/K U Value for Roof - 2.68 W/m2/K
Building Envelope	Double Glazed windows (U value of glass -1.81 W/m2/K and Shading coefficient - 0.26) WWR – 33%	Single Glazed windows (U value of glass -6.97 W/m2/K and Shading coefficient - 0.79) WWR – 48%
Building Lighting Power density	Lighting power density is 7.2 W/m2	Lighting power density 26.5 W/m2
Controls	Daylight controls	No controls or sensors
Building Chiller	3 water cooled screw chillers with COP of 6.1 (rated)	5 water cooled reciprocating chillers with COP of 4.01 (rated)
Energy performance Index (KWh/m2/yr)	55	261

Impact of Low energy strategies

The conventional case was run by incorporating low energy solar passive design strategies on the annual electricity consumption (kWh), electric load (kW) and cooling demand (TR) of the building.

Parameter comparison	Conventional case	Existing case (Low energy strategies)
Electrical load	Base case	12% less than the conventional case
Cooling Load	Base case	16% less than the conventional case
EPI	Base case	22% less than the conventional case

Impact of ECBC Recommended Energy Conservation Measures:

The conventional case was run by incorporating ECBC envelope on the annual electricity consumption (kWh), electric load (kW) and cooling demand (TR) of the building.

Parameter comparison	Conventional case	ECBC compliant case
Electrical load	Base case	60% less than the conventional case
Cooling Load	Base case	55% less than the conventional case
EPI	Base case	55% less than the conventional case

Overall Impact of ECBC and low energy strategies:

The conventional case was run by incorporating both the low energy solar passive design strategies and ECBC envelope on the annual electricity consumption (kWh), electric load (kW) and cooling demand (TR) of the building.

Parameter comparison	Conventional case	ECBC + Low Energy Case
Electrical load	Base case	64% less than the conventional case
Cooling Load	Base case	1% less than the conventional case
EPI	Base case	63% less than the conventional case

Impact of ECBC, Low energy strategies, and ECBC+low energy strategies on conventional case for ITC building, Gurgaon

The above graph shows the variation in the Electrical load (kW), Coil load (TR) and EPI (energy performance index) for all the cases.

The below table gives the comparison of the impact of ECBC, Low energy strategies, and ECBC + low energy strategies on conventional case for ITC Green centre building for a composite climate.

Parameter comparison	Existing case	Conventional case	Low energy strategy	ECBC case	ECBC+Low energy strategy
Electrical load	59% less than the conventional case	Base case	12% less than the conventional case	60% less than the conventional case	64 % less than the conventional case
Coil Load	60% less than the conventional case	Base case	16% less than the conventional case	55% less than the conventional case	62% less than the conventional case
EPI	52% less than the conventional case	Base case	22% less than the conventional case	54% less than the conventional vase	63% less than the conventional case

ECBC Complaint Building, ITC Green Centre, Gurgaon