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Roofs so cool, they gotta wear shades

Portland Tribune

May 15th 2014

For architect Don Sowieja, the present's so bright he has to wear shades. A principal with Portland architecture firm Myhre Group Architects on a recent spring morning Sowieja pulls his shades out as soon as he gets to the roof of the Hollywood Apartments, which he designed.

The 47-unit building at next door to the Hollywood Theater at Sandy Boulevard and Northeast Broadway is typical Portland - mixed use, no parking, rain swales and a stormwater infiltration (dry) well. On a sunny day the roof dazzles like a new Word doc.

"When I started practicing 17 years ago you just did an asphalt roof, and the crazy guys were out there doing this stuff," says Sowieja. "Then within about five years everybody started doing it."

Looking to the sky for relief, contractor Dave Ause adds that 90 per cent of the projects he is now working on have light or cool roofs.

Portland never met a LEED point it didn't like, so it's no surprise that cool roofs are a growing option for architects, developers and construction companies.

Light-color roofs help make buildings cooler and can reduce the impacts of climate change. They reflect back solar radiation, staying relatively cool to the touch. A black topped box acts like a solar oven, which increases the need for air conditioning. Translation: higher electricity bills.

"Green" roofs have a layer of growing medium and hardy plants such as sedum, herbs and grasses. They make good insulation and help slow storm water runoff, but they are expensive and require more maintenance than a sheet of grey plastic, or thermoplastic polyolefin membrane.

Kurt Shickman is executive director of the Global Cool Cities Alliance, a nonprofit which promotes the adoption of white roofs and white pavements globally.

"Cool or white roofs are really taking off in the warmer parts of the world where there reflectivity helps cool buildings that have no air conditioning," Shickman says. "In the U.S. we look at them as a way to reduce the AC load."

He estimates that a flat cool roof can reduce the power demands of AC by up to 20 percent, and a sloped cool roof by 5 to 10 percent on average. Light and dark roofs are now comparable in cost. People generally still prefer visible roofs, that is those on a slope, to look dark rather than light.

Many new commercial buildings are generally getting flat, light-colored roofs, for example Target and Walmart stores. New York, Chicago and Washington, D.C., all have city codes stipulating new cool roofs.

"It's been led by the Green Building Council and LEED," Shickman says. "It's an easy way to get points toward a gold or silver rating. And an architect can easily sell it to a client, because the materials don't cost more."

He notes that the net energy benefits are greater in those cities than in Portland because of the climate.

White is the New Black

Roofs in America are traditionally black because tar and asphalt are black, and they offered the best protection against rain. And matt black absorbs solar radiation like a sponge.

Shickman points out that you can also have a red or a brown roof made of materials that highly reflect the visible and infra red spectrum. "BMW and Mini have been experimenting with cars where the black and red pigments are significantly more reflective than is traditional, so they can downsize the AC units."

The Global Cool Cities Alliance calculates that having cool roofs and pavements in the places where it counts, that is, the world's tropical and temperate climates, could cancel the warming effect of as much CO2 as is put out by 500 coal-fired power plants.

The alliance has all sorts of reasons cool is better. Cool roofs work well around solar panels because less electricity is lost to resistance in a cool wire running from a solar panel than in a hot one. (ReRack, the luggage rack company on at Sandy Boulevard and Northeast 22nd Avenue, has such a roof visible from the street.)

Green roofs benefit because the plants don't dry so readily. It is estimates that roofs make up 25 percent of a city's surface area, and pavement another 40 percent, so there is plenty of scope for reflective roofs and cool roads.

Brian Yauger, chief executive officer of Cool Earth Contracting and Coating in Austin has more than 10 years of roofing and general contracting experience. He has installed roofing for just about every climate variance across the nation.

The Hollywood Apartments building is part of a national wave of white roof construction that is expected to reduce energy use by reflecting light.

"Cool roofs are a huge benefit in warm climates," says Yauger, who is accustomed to 95-degree days in Texas six months of the year.

"On a 95-degree day a black roof can be 170 degrees, it's like having a hot plate on a building. Using our product it only goes up to 105 or 110."

As a contractor, Yauger often uses a reflective epoxy coating, or sprays a polyurethane foam on existing roofs to upgrade them to cool status. It's easier to sell the cool roofs to businesses. Not just small ones, but the owners of strip malls and large building

"It's best for me to talk to the building owner who pays their own electricity bill," he says with a laugh, indicating where the rubber meets the road financially. Code counts too: Austin roofs with more than a 212 pitch (that go up more than two feet in 12) have to be reflective.

Up on the Roof

Looking from the roof of the Hollywood Apartments with an architect's eye, Sowieja adds a dose of reality to the green picture. Even light roofs darken in time. Trader Joe's roof is a mess of puddles and dead leaves. Rite Aid, across Sandy Boulevard, looks like an inefficient building, a single-story box with a black roof (actually a parking lot shared with the Hollywood's residents).

He also point out that cool roofs are standard on the buildings he works on, which are sustainable but which no longer toot their green horn.

Although a building may check all the energy-saving boxes, "Often it's not worth paying the $60,000 it costs to get the LEED certification, when the real point is what gets built, not the label,"Sowieja says, of a process where architects are often under pressure to build the best building for the lowest cost.