Raising a Green Roof

Retrofitting an existing roof and boosting insulation can reduce one family's cooling costs.

Homeowner and carpenter Jeff Wilson is doing a Deep Energy Retrofit (DER) of his 70-year-old home with the ultimate goal of cutting his energy bill to zero.

That meant retrofitting the existing roof and boosting insulation to reduce the family's cooling costs by up to 17 percent. Plus, by applying new spray-foam insulation, radiant sheathing and eco-smart roofing on top of the existing surface, Jeff didn't fill any dumpsters in the process.

Jeff needed a bigger, more energy efficient roof to connect with a new addition. I-joists (beams made of engineered wood) were nailed into the existing roof to raise the roof angle of the entire back of the house to create a flatter surface to support solar panels.

The "higher" roof created by the I-joists also would allow for a 13-foot ceiling on the addition's second level.

Jeff used Louisiana Pacific engineered lumber, which has a 50-year warranty and is made from small-diameter, fast-regenerating trees. It's much better than using wood from a large tree, plus its bonding elements contain no formaldehyde.

This is a view of the front of the house, showing 2x4s installed as purlins and rafters. Spray-It-Green insulation will fill in the gaps, creating an air-tight surface on which to lay sheathing and roofing material.

Jeff shoots Spray-It Green foam insulation in between beams. He applies about 2 1/2 inches to the front roof and 3 1/2 inches to the back roof, which will support a solar panel system and be roofed with a different material.

Next comes a layer of sheathing. Rather than standard sheathing, Jeff opted for an eco-upgrade: TechShield radiant barrier sheathing from Louisiana Pacific. A shiny, aluminum underlayer on the sheathing faces the house, preventing heat from penetrating into the attic.

In this photo, you can also see the back part of the roof, which was raised with I-joists.

Jeff's team installs radiant sheathing in the same manner traditional oriented strand board (OSB) sheathing is applied: on top of rafters and underneath roofing material.

"That simple layer of aluminum laminated on the underside of the sheathing can reduce attic temperatures by up to 30 degrees and save us up to 17 percent on air conditioning costs," Jeff says.

The steep-sloped roof at the front of the Cape Cod home was shingled with Eco-Star, a recycled rubber product that resembles slate. Its gray color keeps the roof cooler than black asphalt-fiberglass shingles.

The green Eco-Star roofing material has a 50-year warranty and will last up to 75 years. "I'll never have to replace this roof," Jeff says, pleased with his investment. The material costs about three times more than asphalt shingles.

Jeff estimates the energy rating, or R-value, of his front roof is about R-40, and the back roof is near R-50.

Eco-Star roofing is applied in an offset pattern to add character to the front of the home, in keeping with its Cape Cod style. The special treatment cost a few hundred dollars more in labor, but the payoff is an aesthetically appealing surface. "We wanted to make as much of a statement as we could," Jeff says.

The rear dormer roof was covered with Weather Bond Weld-Free TPO, a heavy-duty rubber roof that's thin, stretchy and will work hard to keep heat away from the solar panels Jeff plans to install on them.

"Photovoltaic panels operate best at a moderate temperature, so if the roof heats up to more than 100 degrees, the solar panels lose their efficiency," Jeff explains. "The white shingles will give us a much lower surface temperature, even on a really hot day." And aesthetically speaking, the white rubber roofing is not visible from the curb.

In this photo, you can see the two different energy efficient roofing materials used on the Wilson home: the gray Eco-Star product in the front and the white Weather Bond product in the back. While the products may look mismatched, this doesn't matter since passers-by won't notice the back roof.

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