A cost-competitive reflective roof membrane reduced the average summertime daily maximum roof-surface temperature of a retail store in Austin, Texas, from 168°F (76°C) to 126°F (52°C). The total air-conditioning energy use was thereby reduced by 11% and peak air-conditioning demand fell by 14%. This 100,000 square foot building is predicted to save about $65,000 over the life of the roof.
The average daily maximum roof-surface temperature for the black roof was 168°F (76°C). For the white roof it was reduced to 126°F (52°C). Similarly, the average maximum plenum temperature was reduced from 101°F (38°C) to 95°F (35°C). The average daily a/c savings were 355 kilowatt-hours (11% of total a/c use, saving about $750/month) and the peak-demand reduction was 35 kilowatts (14% of peak a/c demand, saving about $490/month) in the summer. We estimate that the installation of this cool roof saves over 60 megawatt-hours per year; the total annual energy- and peak-demand savings are estimated at $7,200. The total discounted savings over the expected life of the roof are estimated to be $60,000 to $70,000.
S. Konopacki and H. Akbari. 2001. Measured Energy Savings and Demand Reduction from a Reflective Roof Membrane on a Large Retail Store in Austin. Lawrence Berkeley National Lab
Publication Date: June 2001
Get the file:
- Measured Energy Savings and Demand Reduction from a Reflective Roof Membrane on a Large Retail Store in Austin