Adopting Low-cost Alternative for Energy Saving
Case Study

General Information:

City: Bangalore
Climate: Temperate
Operational schedule – Day use, 5 working days in a week
Area of the building: 13635 m² (out of which 13010 m² - conditioned area, 625 m² - non-conditioned area)

Function: Office space

Existing Building Design Features

Building Envelope


230mm brick wall with 30mm
plaster on exterior side and 20mm on interior side


The U-value is higher than that of ECBC recommended (0.409 W/m2K).
This results in high external solar heat gains and increased cooling loads


6mm clear single glazed window in the thermally unbroken aluminium frames

(SC – 0.69, U- Value of Glass – 5.7W/m2K) WWR – 60%

Clear single glazed window and WWR which is more than that of ECBC recommended (40%) increases the external solar heat gain and the cooling loads

Building Lighting

Lighting system

  • 14 % of the total connected load (150 kW during daytime)
  • 36W OSRAM high lumen slim tube lights in the office space, 150W HPSV lamps
  • Copper chokes are used
  • The LPD for different towers of the building:
    • Tower I – 15.06W/m2
    • Tower II – 17.21W/m2
    • Tower III – 21.41W/m2
    • Tower IV – 10.76W/m2
  • Most of the LPD values are higher than the ECBC recommended (11.8W/m2) for office space which has high energy consuming potential
  • Lighting energy consumption – 19.9%
HVAC system Design
  • Central AC plant with 3 air cooled screw chillers, 2 of 300TR and 1 of 240TR
  • The COP of the chillers is 3.07 (rated) / ECBC recommended is 3.05
  • Rated Sqft/TR – 167
Energy Performance of the Building

Lighting Energy Performance of the Building

  • Annual Consumption (lighting) – 20%
  • Lighting Performance Index – 61 KWh/Sqmt/annum

Space Conditioning Energy Performance of the Building

  • Annual Consumption (A/C) – 80% of the total
  • HVAC Performance Index – 259 KWh/Sqmt/annum

Annual energy consumption due to lighting & air conditioning (kWh): 4208963

Energy Performance Index of the building (KWh/sq.mts of built up area/annum): 309

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