Calculator of energy savings (cooling-heating) for low-slope roofs (relative to a "black" roof)

   Input data
   Output data

   Country

   City
   Roof  
       R-value (high=3.5; avg=1.5; low=0.5 )

K·m²/W

   Net savings

€/m² per year
       Solar reflectance, SR (high=80; avg=50; low=10)

%        

   Cooling savings

€/m² per year
       Infrared emission, IE (high=90; avg=60; low=10)

%        

   Heating savings (heating penalty if negative)

€/m² per year
   Energy costs and equipment efficiencies

   Insulation in black roof to yield same annual energy savings:

(visit Europe's Energy portal for help)

    Upgrade from R- to R- K·m²/W 
   Summertime cost of electricity
   (high=0.30; medium=0.15; low=0.08)
 €/KWh   
 		 
   Air conditioner efficiency (cooling COP)
   (high=4; avg=3; low=1.5) 

   Details of comparison

   Energy source for heating (choose one)

Electricity Fuel 

    Heating degree days for location chosen annual °C-day 
   If electricity, wintertime cost 
   (high=0.30; avg=0.15; low=0.08)
 €/KWh    Cooling degree days for location chosen annual °C-day 
   If fuel, cost      
   (Natural gas: high=0.15; avg=0.09; low=0.03)
  (Heating oil: high=0.09; avg=0.07; low=0.05 = € per litre/12.24)
 €/Kwh    Solar load for location chosen annual average KWh/m² per day 
   Heating system efficiency (heating COP)  
   (Furnace or boiler: high=0.8; avg=0.7;low=0.5)
   (Electric heat pump: high=2; avg=1.5)
   (Electric resistance: 1) 

   Cooling load for black roof (SR=5%; IE=90%)

 KWh/m² per year
   Heating load for black roof (SR=5%; IE=90%) KWh/m² per year
     Cooling load for proposed roof KWh/m² per year
   Heating load for proposed roof KWh/m² per year

 

- Developed in the framework of EC's "CoolRoof" project.

- The accuracy of this calculator depends on the supplied data. CLICK HERE to get help in figuring out the best input values.

- The model used for estimating savings is adapted from the paper of Petric et al., "Effect of solar radiation control on energy costs - A radiation control fact sheet for low slope roofs", Proceedings, Performance of the exterior envelopes of whole buildings VIII: Integration of Building envelopes, Atlanta, December 2001, American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc.