Adopting Low-cost Alternative for Energy Saving
Case Study

Solar Passive Design Building, Transport Corporation of India Ltd (TCIL), Gurgaon

General Information:

Client: Transport Corporation of India Ltd (TCIL)
City: Gurgaon
Climate: Composite
Operational schedule – 6 days and 12 hours
Area of the building: 3058m² (out of which 2607 m² - conditioned area, 451 m² - Non- conditioned area)

Green Building Design Features:

Building Design


Orientation: NE, SW
This helps in receiving less radiation which results in lesser heat gains and reduced the overall air-conditioning requirement and hence saves energy. Proper orientation also helps in receiving natural light and ventilation

Building Height

Minimum height above the ground level to limit exposure to external conditions. Recessed windows to reduce external solar heat gains.

Water Body

Fountain to flow over extensive surfaces to maximize evaporation. Water evaporation has a cooling effect in the surroundings.

Building Envelope


Insulation helps retain cool in summer and heat in winter, and acts as sound proof. This can create a major impact on indoor thermal comfort of the building.

Compact floor plan with external walls


Single glaze recessed windows

  • Single glazed unit helps in integrating optimum daylight
  • Recessed windows and optimum WWR (Window Wall Ratio) which is less than ECBC standard (40%) helps in reducing external solar heat gain

(SC – 0.52, U-value of Glass – 5.7 W/m2K)


35 mm thickness insulation with reflective glazed tile paving

U-value = 1.01 W/m2K

The glazed tile reflects heat off the surface because of the high solar reflectivity and infrared emittance which prevents heat gain and thus helps in reducing the cooling load from the building envelope.

Building Lighting

Day light integration

Window area minimized to 14% of the external wall area, small peep windows at seating height and large windows at ceiling level

Small windows at the seating areas can reduce thermal discomfort.
The reduced percentage of window area to wall area helps in reducing the external heat gain into the building.

Lighting system

9% (18.10 KW of indoor lighting) of the total connected load for the building.
Luminaires used – down lighter recessed type CFLs, electronic ballasts used mostly.
LPD – 5.9 W/m2

  • The percentage of the lighting load to the total load shows that there is very less percentage of artificial lighting used in the building
  • The electronic ballasts save approx 20-30% in energy consumption over the standard ballasts.
  • The LPD (5.9 W/m2) is less than the max allowed LPD of ECBC (10.8 W/m2) which is very good.
HVAC system Design
  • Central plant with 2 vapour chillers
  • Total cooling capacity is 125 TR
  • Co-efficient of performance – 4.21
  • operating Sqmt/TR-39
Energy Efficiency controls

No energy efficient controls

Energy Performance of the Building

Lighting Energy Performance of the Building

  • Annual consumption (lighting) – 69232 kWh
  • Total built space – 3058
  • Lighting performance index – 23 kWh/sqmt/annum

Space Conditioning Energy Performance of the Building

  • Annual consumption (A/C) – 376102 kWh
  • HVAC performance index – 144 kWh/sqmt/annum
  • Operating cooling demand – 39 sqt/TR

Annual energy consumption due to lighting & air conditioning (kWh): 445335

Energy Performance Index of the building (KWh/sq.mts of built up area/annum): 147


Comparison of various parameters for solar passive building (TCIL) with conventional case

Parameters Solar passive Case (Existing Building) features Conventional Case (Building features)
Building orientation Building orientation : Longer facades of the building facing 45 deg to the North

Building orientation: Longer facades of the building facing East-West
Windows, Walls and Roof are not shaded Windows, Walls and Roof are not shaded
Building Envelope

Insulation on roof with air gap for walls
U value for Wall -1.67W/m2/K
U Value for Roof- 1.01 W/m2/K

No insulation on wall and roof.
U value for Wall-1.98 W/m2K
U Value for Roof: 1.76 W/m2K

Window glazing : U value of glass - 6.17 W/m2/K
and Shading coefficient- 0.52
WWR : 11%

U- Value of Glass – 6.17W/m2K and Shading coefficient – 0.61
WWR – 11%

Building Lighting Power density Lighting power density is 6.3 W/m2
Lighting power density 20 W/m2
Controls Occupancy sensors No controls or sensors
Building Chiller 2 * 62.5 TR Water cooled vapor absorption chiller
PTAC units having EER of 8.4 and Fan power as 0.000134 bhp/cfm
Energy performance Index (KWh/m2/yr) 147 170

Energy Saving Potential

The conventional case defined above was selected to run different energy saving options and to finally quantify the energy saving potential which can be realized in composite climate by incorporating the low design strategies, ECBC envelope, and the best case (incorporating both low energy strategies and ECBC measures)

Impact of ECBC, Low energy strategies, and ECBC + low energy strategies on conventional case for TCIL building, Composite climate

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


Parameter comparison Existing case Conventional   case Low energy strategy ECBC case ECBC+Low energy   strategy
Electrical load 18% less than the conventional case Base case 25% less than the conventional case 41% less than the conventional case 50% less than the conventional case
Coil Load 18% less than the conventional case Base case 24% less than the conventional case 46% less than the conventional case 57% less than the conventional case
EPI 14% less than the conventional case Base case 33% less than the conventional case 17% less than the conventional vase 35% less than the conventional case

Copyright 2012. All rights reserved by HPCB Privacy Policy