Roof Surface Temperature

A cool roof under the same conditions could stay more than 50 f cooler and save energy and money by using less air conditioning.

Roof surface temperature.

An approximate equation for the sol air temperature ts of the outside surface of a given wall or roof is. Different sources report different temperatures. 138 145 but feels hotter to the touch than a black roof. Cool roofs can be made of a highly reflective type of paint a sheet covering or highly reflective tiles or shingles.

The average temperature difference through the day was about 2 degrees f. The difference between the maximum temperatures of black and white vertical surfaces is about 50 f degrees compared with 60 f degrees for horizontal surfaces. If the roof considered in figure 2 had a white instead of black surface i e. Standard or dark roofs can reach temperatures of 150 f or more in the summer sun.

A 0 4 instead of 0 9 the surface temperature would be 130 f instead of 190 f. A comparison of hourly values given in figures 3 and 4 for cloudy and clear days respectively indicates a greater discrepancy for clear days. Most of the roughly 2 percent of the earth s land surface covered in urban development suffers from some level of urban heating. Measured and calclrlated heat flow for a clolrdy day 3 april follo vi g a day with fairly clolrdy conditioirs.

Fresh asphalt reflects only 4 percent of sunlight compared to as much as 25 percent for natural grassland and up to 90 percent for a white surface such as fresh snow. Department of energy. This fsec study didn t look at shingle lifetime but i think that adding 9 degrees to a temperature of 150 degrees won t make much difference. What kills shingles isn t so much the temperature.

Overall the plywood sheathing in black shingled roof systems tended to be 10 f to 15 f 5 c to 8 c warmer dur ing the midafternoon of a sunny day than the plywood in comparable white shingled roof systems. Ts to a id is hso a absorption coefficient of outside surface id direct solar radiation on surface. Up to 68 degrees cooler than black roofs. The maximum sheathing temperatures recorded were 168 f 76 c for black shingled roofs and 147 f 64 c for white shingled roofs.

On a hot sunny day the temperature on the surface of a traditional black roof can be more than 50 degrees fahrenheit 10 degrees celsius warmer than the surrounding air temperature source.