Roof Surface Temperature

A comparison of hourly values given in figures 3 and 4 for cloudy and clear days respectively indicates a greater discrepancy for clear days.

Roof surface temperature.

Measured and calclrlated heat flow for a clolrdy day 3 april follo vi g a day with fairly clolrdy conditioirs. Most of the roughly 2 percent of the earth s land surface covered in urban development suffers from some level of urban heating. Cool roofs can be made of a highly reflective type of paint a sheet covering or highly reflective tiles or shingles. Roof surface degrees fahrenheit on a sunny 90 degree day.

The average temperature difference through the day was about 2 degrees f. 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. 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. Different sources report different temperatures.

If the roof considered in figure 2 had a white instead of black surface i e. On roof summer temperatures for asphalt shingles 10 76 c about 50 f to 170 f research on shingle durability tests asphalt shingles at temperatures typically up to a maximum of about 170 f well below the temperatures that occur during manufacture of the product. An approximate equation for the sol air temperature ts of the outside surface of a given wall or roof is. 138 145 but feels hotter to the touch than a black roof.

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. 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. The maximum sheathing temperatures recorded were 168 f 76 c for black shingled roofs and 147 f 64 c for white shingled roofs. Up to 68 degrees cooler than black roofs.

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. What kills shingles isn t so much the temperature. A 0 4 instead of 0 9 the surface temperature would be 130 f instead of 190 f. Standard or dark roofs can reach temperatures of 150 f or more in the summer sun.

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