Measured temperature reductions and energy savings from a cool tile roof on a central California home

To assess cool-roof benefits, the temperatures, heat flows, and energy uses in two similar single-family, single-story homes built side by side in Fresno, California were measured for a year.  The “cool” house had a reflective cool concrete tile roof (initial albedo 0.51) with above-sheathing ventilation, and nearly twice the thermal capacitance of the standard dark asphalt shingle roof (initial albedo 0.07) on the “standard” house.

Cool-roof energy savings in the cooling and heating seasons were computed two ways.  Method A divides by HVAC efficiency the difference (standard − cool) in ceiling + duct heat gain.  Method B measures the difference in HVAC energy use, corrected for differences in plug and window heat gains.

Based on the more conservative Method B, annual cooling (compressor + fan), heating fuel, and heating fan site energy savings per unit ceiling area were 2.82 kWh/m2 (26%), 1.13 kWh/m2 (4%), and 0.0294 kWh/m2 (3%), respectively.  Annual space conditioning (heating + cooling) source energy savings were 10.7 kWh/m2 (15%); annual energy cost savings were $0.886/m2 (20%).  Annual conditioning CO2, NOx, and SO2 emission reductions were 1.63 kg/m2 (15%), 0.621 g/m2 (10%), and 0.0462 g/m2 (22%).  Peak-hour cooling power demand reduction was 0.88 W/m2 (37%).

Suggested citation or credit:

Energy and Buildings, Volume 80, September 2014, Pages 57–71

Additional credits:

David Faulkner
Lawrence Berkeley National Laboratory, Berkeley, CA, United States

Douglas P. Sullivan
Lawrence Berkeley National Laboratory, Berkeley, CA, United States

Ronnen Levinson
Lawrence Berkeley National Laboratory, Berkeley, CA, United States

Source: Elsevier

Publication Date: September 2014

Find it at:

See more: