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Lowering energy use with a new roof

My black asphalt shingle roof needs to be replaced. I want to install a new roof that will last longer and help keep my home cooler during hot summer afternoons. What type of roof do you recommend?—Sandi J.

That depends on your budget. Asphalt shingles are the least expensive option to buy and install, but they show wear and tear quickly and may need to be replaced sooner than you’d like. Although metal roofing can cost twice as much as a shingle roof, many types have lifetime warranties.

If you use shingles, for the best energy efficiency and effectiveness in reflecting the sun’s heat, choose the lightest color you find attractive. It takes very little color tint before shingles start to absorb and retain heat, so white is the best choice. But, due to the way shingles are installed, there will still be some direct heat transfer to the roof’s sheathing below.

I installed an aluminum simulated shake roof on my own home five years ago. My roof consists of 1 x 2-foot interlocking panels with a special heat-reflecting paint coating. The panels are made of recycled aluminum from soda cans and are formed to look like cedar shakes.

The advantages of metal

Aluminum and steel are the two most common and reasonably priced roofing materials. The advantage to metal roofs has to do with the materials used and how they are installed. Certain metals have low emissivity, a word that describes a material’s ability to release absorbed heat. For an aluminum roof’s low-emissivity properties to be the most effective, choose a style with a contour that provides an air gap over the sub-roof sheathing to prevent any direct heat transfer. My roof looks like cedar shakes, but an aluminum roof shaped to simulate clay tiles can also be very energy efficient.

After my aluminum roof was installed, the bedrooms on the second floor of our home stayed much cooler during summer afternoons.

Other metal roof options include painted steel roofs, which are available in many colors and simulated contours. The steel is treated with many layers of corrosion-resistant coatings, so rust is not a problem. Steel roofs with an aluminum-alloy coating are particularly durable.

Proper roof vents improve efficiency

Whether you choose white shingles or a metal roof with heat-reflecting paint, also consider installing an attic ridge vent. Adequate attic ventilation helps with both summer and winter energy efficiency. When replacing a roof, adding a ridge vent is a minor additional expense. Also check that your existing soffit vents are not blocked by attic insulation.

James Dulley from the August 2015 issue.

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