Adopting Low-cost Alternative for Energy Saving
Case Study

General Information:

Client: Himachal Pradesh State Government Secretariat
City: Shimla
Climate: Cold
Operational schedule – 7 hours, 6 working days in a week

Green Building Design Features:

Building Design

  • Longer Facades: NE-SW
  • NE façade gets a certain amount of daylight and solar heat due early in the mornings.
  • SW facade has more optimum amount of daylight and solar heat in winter months

Building Envelope


Walls of air-conditioned zones in all blocks – 230mm brick with 12.5mm plaster


150mm concrete slab with cement tile

  • 6 mm clear single glazed windows
  • Clear glass helps in receiving required amount of solar heat gain in early mornings and winter months which is required in cold climate of Shimla
  • SC – 0.87, U-value of Glass – 5.8 W/m2K, WWR – 50%

Building Lighting

Lighting system
  • Lighting system accounts for 29.7% (indoor: 95kW)
  • Luminaries used: mostly open type luminaires in office spaces, CFLs with electronic ballasts in corridors
    and florescent lamps in storages, electrical and mechanical rooms
  • LPD – 7.72W/m2
  • The LPD (7.72W/m2) is less than the max allowed LPD of ECBC (10.8W/m2), which is very good
  • The electronic ballasts saves approx 20-30% in energy consumption over the standard ballasts
  • Good natural light available in office spaces
HVAC System Design
  • Central heating plant with capacity of 1470kW
  • Block1: 630kW, Block2: 840kW
  • COP: 1 (rated)
Energy performance of the building

Lighting Energy Performance of the Building

  • Annual Consumption (lighting) – 356044 KWh
  • Lighting Performance Index – 28 KWh/Sqmt/annum

Space Conditioning Energy Performance of the Building

  • Annual Consumption (A/C) – 518208 KWh
  • HVAC Performance Index – 41 KWh/Sqmt/annum

Annual energy consumption due to lighting & air conditioning (kWh): 437,126

Energy Performance Index of the building (annual energy consumption in lighting and AC system/ total built up area):70 kWh/m2/yr

Comparison of various parameters for solar passive design strategies(ARMSDALE) with conventional case

Parameters Solar passive Case (Existing Building) features Conventional Case (Building features)
Building orientation Building longer facades are facing SW-NE

Building Longer East-west orientation
No roof and wall shading No roof and wall shading
Building Envelope

No insulation on wall and roof.
U value for Wall -1.92 W/m2/K
U Value for Roof-2.74W/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

Single Glazed windows (U value of glass - 5.8 W/m2/K and Shading coefficient - 0.87)
WWR – 50%

Single Glazed windows (U value of glass - 4.3 W/m2/K and Shading coefficient - 0.89)
WWR – 28%
Building Lighting Power density Lighting power density is 7.72 W/m2
Lighting power density 12.4 W/m2
Building Chiller 2 centrally heating plants each capacities of 630kW and 840kW 2 boilers of 600 kg/hr
Energy performance Index (KWh/m2/yr) 70 237
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