Buzzword: Cool Roof

What it means. Never heard of a "cool roof"? Abandon your visions of an overhyped hipster-filled rooftop bar or eatery in an edgy, funky neighborhood. A cool roof, simply put, is a roof designed to reflect sunlight. Since the roof stays cooler, less heat is transferred to the building below, resulting in a cooler building and energy and money savings.

Why the buzz? U.S. Secretary of Energy Steven Chu recently made headlines when he was in London to attend a symposium on climate change. He said that painting all roofs white or light colors could help significantly reduce the amount of energy used to cool buildings.

But this idea is about not only the color of a roof but also its solar reflectance (SR) and thermal emittance (TE), which are rated on a scale of 0 to 1, with 1 being the most reflective or emissive. The Cool Roof Rating Council trade group says it rates products based on their initial values and after three years of weather exposure. The cool-roof concept is to use reflective coatings or materials. So a cool roof could be made of clay or concrete tiles or other materials suitable for a climate along with coatings in a range of colors that are designed to reflect the rays of the sun. The photo shows a home with MCA clay roof tiles in Riverside, California.

Cool roofs lower the surface temperature of a roof by up to 100*F, according to the California Energy Commission, which estimates that cool roofs can trim cooling costs by 20 percent on average in California. The CRRC estimates the average energy savings are 7 to 15 percent of cooling costs.

But the U.S. Department of Energy says that reflective roofs don't work in all situations, and the biggest benefits are reaped in hot, sunny climates where air conditioning is used frequently. Homes in shady spots or those with well-insulated attics might not see significant benefits. Cool roofs can also increase heating costs in the winter. To figure out how much energy you'll save, use the DOE's cool-roof calculator.

If you are considering a cool roof, find out whether the materials qualify for a federal tax credit and request a manufacturer's certification statement. You could receive a 30 percent tax credit (up to $1,500) for the material costs if the roof is installed this year or next. Also look online for rebates from utility companies.—Kimberly Janeway | e-mail | Twitter | Forums | Facebook

Essential information: Check out our June 2009 report on roofing and July 2009 report on air conditioning (available to subscribers), stay cool without sky-high energy bills, and read about ceiling fans.

Comments

[Kim Price]

I had a new roof installed on my home about 2 years ago and thought about the effects on heating and cooling when choosing a color.

I thought black would look best, but because heat bothers me way more than cold, I was concerned about the added heat having a black roof generate.

However, as I live in Oregon and not only spend way more to heat my house than I do to cool it, but I heat for 6 months and only cool during 4 months and certainly not every day.

Because of that, it seemed to me that a "hot" roof would be a better choice. I went with black and have been very happy with it.

[Bob]

"I was concerned about the added heat having a black roof generate. However, as I live in Oregon and not only spend way more to heat my house than I do to cool it, but I heat for 6 months and only cool during 4 months and certainly not every day. Because of that, it seemed to me that a "hot" roof would be a better choice. I went with black and have been very happy with it."

Apparently you didn't read the article:
"But the U.S. Department of Energy says that reflective roofs don't work in all situations, and the biggest benefits are reaped in HOT, SUNNY CLIMATES climates where air conditioning is used FREQUENTLY. Homes in shady spots or those with well-insulated attics might not see significant benefits. Cool roofs can also increase heating costs in the winter."

The article is referring to those who live in the South and Southwest, not people in forested parts of Oregon! Incidentally, many people with modest homes using flat or semi-flat roofs in the Southwest HAVE USED WHITE REFLECTIVE ROOF COATINGS FOR DECADES. Apparently Steven Chu, who lives in Palo Alto (40-70 degrees F year round), only recently found out about the subject.

[Jenni]

My fiance and I are looking into putting on a new roof on our first home together. It is a 1925 Spanish Mission in South Florida. The cool roof seems ideal. It is a flat roof with tar and stone. I read reviews and I would think that a white reflective roof would be the best bet. How would I get a price point? Any positie comments would help. Thanks all.