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

Case Study

General Information:
Client: Hindustan Unilever Limited
City: Bangalore
Climate: Moderate
Operational schedule – 8.30 hours, 5 working days in a week
Area of the building: 10,714m² (out of which 5665 m² - conditioned area, 5049 m² - non-conditioned area)

Green Building Design Features:

Building Design

Orientation

Longer facades: N-S
Large window openings: N-S
Blank walls on E-W (separate layer of outer walls on East)
West shaded by existing buildings
Building orientation has been a significant design consideration
Large window openings on N-S for daylight integration
Separate layer of outer wall on east shades the building on east facades and reduces the solar heat gain

Landscape

Buildings designed around the existing mature trees
Circulation areas designed around these trees
Prevent heating up of building surface and reduces direct solar heat and heat island effect
Circulation areas designed around these trees make these areas naturally daylit and ventilated
Shade the semi-open circulation and meeting areas

Water Bodies

Reception areas as well as research building blocks surrounded by water bodies
Water bodies – major modifiers of micro-climate around the building
Evaporative cooling through water bodies lower the temperature of micro-climate by evaporating water
Helps in maintaining thermally comfortable circulation areas and semi-open spaces

Walls

Separate layers of wall of E-W orientation to shade from high intensity of solar radiation
Walls on west adjacent to existing buildings to prevent solar heat gain and to shade the building

Roof

Windows

Blue-Grey glass 6mm single glaze window with shading provided
Tinted glass with shading on all windows helps in reducing solar heat gain and also the problem of glare

Building Lighting

Day light integration

Sky lights extensively used in common areas, circulation areas with no artificial lights
Labs are also well day lit
Natural day light integration through skylights and atrium spaces helps in reducing annual electricity consumption due to artificial lights

Occupancy sensors

Occupancy sensors in the laboratories
Reduce energy by turning the lights on when someone enters the room and switches when the room is empty

Lighting System

11.65% of the total connected load for the building (connected load of lamps 49.4kW)
Luminaires used – mostly FTLs, CFLs, and Sodium Vapour Lamps
Translucent glass for roof in between I, II, III & IV blocks
LPD – 6.3W/m2
The LPD (6.3W/m2) is less than the max allowed LPD of ECBC (10.8W/m2) which is very good
According to Energy Star, CFLs provides the same amount of light as ordinary bulbs using 75% less energy
Translucent glass to make use of natural lighting and reduce the electricity consumption due to artificial day light during day time

HVAC system design

3 water cooled screw type chillers
Total cooling capacity is 360TR
Chiller COP (rated) – 4.23
Operating Sqmt/TR – 24

Energy performance of the building

Lighting Energy Performance of the Building

Annual Consumption (lighting) – 220103.3 KWh
Lighting Performance Index – 21 KWh/Sqmt/annum

Space Conditioning Energy Performance of the Building

Annual Consumption (A/C) – 593985.9 KWh
HVAC Performance Index – 105 KWh/Sqmt/annum

Annual energy consumption due to lighting & air conditioning (kWh): 814089.2

Overall Energy Performance Index due to lighting & air conditioning (kWh/m2): 76

Energy Saving Potential

Comparison of various parameters for solar passive building (HUL, Bangalore) with conventional case

Parameters	Solar passive Case (Existing Building) features	Conventional Case (Building features)
Building design	Building longer facades are facing North-South.	Building orientation was changed to 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 - 1.32 W/m2/K U Value for Roof - 0.97W/m2/K	No insulation on wall and roof. U value for Wall - 1.92 W/m2/K U Value for Roof - 3.35 W/m2/K
Building Envelope	Single Glazed windows (U value of glass - 5.7 W/m2/K and Shading coefficient - 0.47) WWR - 50%	Single Glazed windows (U value of glass - 5.79 W/m2/K and Shading coefficient - 0.69) WWR – 60%
Building Lighting Power density	Lighting power density is 6.3 W/m2	Lighting power density is 10.76-21.41 W/m2
Controls	Occupancy sensors in the laboratories	No controls or sensors
Building Chiller	3 water cooled screw chillers with COP of 4.23 (rated)	Air cooled screw chillers with COP of 3.08 (rated)
Energy performance Index (KWh/m2/yr)	76	309

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	27% less than the conventional case
Cooling Load	Base case	30% less than the conventional case
EPI	Base case	18% less than the conventional case

Impact of ECBC envelope

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	Existing case ECBC envelope
Electrical load	Base case	12% less than the conventional case
Cooling Load	Base case	10% less than the conventional case
EPI	Base case	9% less than the conventional case

Overall Impact of Low energy solar passive design strategies, ECBC measures and HVAC controls

The conventional case was run by incorporating both the low energy solar passive design strategies, ECBC measures and HVAC controls 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 + ECBC recommended strategies + HVAC controls
Electrical load	Base case	49% less than the conventional case
Cooling Load	Base case	34% less than the conventional case
EPI	Base case	34% less than the conventional case

Solar Passive Design Building, Hindustan Unilever Limited, Bangalore