How To Design A Living Roof That Saves Energy

A bright, spacious house in Maine showcases eco-friendly architecture at its luscious best.

                          

                 For a private home he designed in Bremen, Maine, architect Chris Briley created a green roof that covers the entirety of the long slope topping the structure. “That’s the thing that jumps out at everybody,” chuckles Briley, of the Maine firm Briburn. “When I first proposed it, I asked, ‘How do you guys feel about vegetated roofs?’”

The homeowners—book resellers seeking a waterside residence—turned out to be entirely amenable to the idea of a roof that is not only visually distinctive but also keeps the house cool in the summer and reduces stormwater runoff, protecting the nearby pond. “Everyone asks, ‘Do you have to go up there and mow it?’” Briley continues. “Of course you don’t because it’s alpine sedums, not grass, and it’s planted on engineered soils, which are high in nutrients and minerals but drain very quickly.” During installation, the plants were hoisted atop the roof on pallets. The lush carpet of sedums, a hardy flora that Briley likens to “cold-climate cactuses,” is ideal for conditions on the roof.

The roof may be the talking point, but the entire house is a veritable case study in sustainable design. In fact, the client originally found Briley after he wrote an article about what it really means to be green. Taking a stand against superficial greenwashing, Briley has long believed that sustainable design is about “making fantastic, durable spaces that will stand the test of time, not just from a construction standpoint but also from a livability standpoint.”

To that end, the homeowner approached Briley with the open-ended brief to design “a house that looks like it belongs here,” on the location of a wooded, 58-acre site next to Maine’s Pemaquid Pond.

Given only a loose constraint of materials (the couple wanted wood, glass and stone), Briley enjoyed free rein to design an airy, generously lit space, achieving a timber-frame effect with post-and-beam construction. A well-appointed kitchen anchors the first floor—notable details include the floating all-glass cupboard and the curved countertop of the center island—while the master bedroom and study overlook the double-height living room. Douglas fir, used for the structural elements, appears throughout the interior, including in the floor-to-ceiling bookshelves at the heart of the space.

Briley acknowledges that building materials have come a long way since the completion of the house in 2010, when sustainable materials were much harder to come by. From the solid-wood doors to the custom cabinetry (made from formaldehyde-free plywood), he notes that the low-VOC adhesives and paints were cutting-edge at the time but are now relatively standard.

Meanwhile, the house is clad with thermally modified poplar, a tropical hardwood harvested in the Northeast: “It’s cooked in an oxygen-free environment, so it can’t ignite, which steams out all of the nutrients, making it really unattractive to both pests and bacteria that cause mold and mildew,” says Briley.

But back to the living roof. Briley designed it so it lets in the winter sun but cuts off the steeper angle of the summer sun. That helps to moderate the temperature within the house, preventing direct sunlight from heating the home in the warmer months. The detached garage is planted with alpine sedums and topped with a 90-tube solar-collector array, which easily provides all of the domestic hot water and upwards of 50 percent of the space heating to offset the boiler. Now that’s a roof worth talking about.