JOHN D. WAGNER: Cool Roofs Save Energy
New study shows: Grow your sales by sharing the science and value of today’s cool roofing products.
BY: JOHN D. WAGNER
It’s a common fact that black roofs get hotter than white roofs, and air flowing under a roof will cool it and frustrate heat transfer to the structure. The benefits of cooler roofs have long been known, but a new study of flat roofs quantifies the savings, while comparing flat white roofs to black roofs and to so-called living green roofs.
Let’s start with some basic stats taken from residential roof science: A roof with black shingles reflects about 5% of the sun’s heat, and a roof with gray shingles reflects back about 20% of the sun’s heat. White shingles reflect around 25%. That 20% differential between a black roof and white roof is nothing to sneeze at. Black roofs get as much as 90 degrees hotter than white roofs, which drives up the cooling load, meaning that the house consumes more power to run the AC. EPA figures show that $40 billion is spent each year in the U.S. to cool buildings, around 15% of all the electricity, lots of which is generated by coal. So savings from white roofs or roofs that are shingled with EPA-rated cool-roof shingles can have meaningful benefits.
But now, a new report focused on commercial roofs by the Lawrence Berkeley National Laboratory says white roofs are indeed the optimal choice. And if someone were considering a living roof, where vegetation absorbs water and cools the roof, note that the report says that white roofs are “three times more effective than living green roofs at cooling the globe.”
The report is focused on flat roofs, which are typically EPDM, a synthetic rubber made of ethylene and propylene. The authors looked at 22 commercial flat roof projects and found that white roofs provide a 50-year net savings of $2.40/square feet relative to black roofs, but that living green roofs have a net cost of $6.60/square feet. “Despite lasting at least twice as long as white or black roofs, green roofs cannot compensate for their installation cost premium,” the report found.
Although the study focused on commercial structures, the central point is clear: White roofs save energy and lower roof maintenance.
The thing is, no one wants white shingles on their home, unless they’re building a vacation home in Florida, and even then the glare will blind you.
The free market to rescue.