Blue Hill cottage example of ecological building
April 2, 2009
Contact: Jim Bannon
Village Green Timber Frames of Blue Hill has just finished building a cottage that it says is an example of ecological building. Built almost entirely of wood, stone, earth and straw using traditional techniques, the 1000-square-foot building relies on a passive solar design and abundant insulation to keep heating energy costs at a minimum. “There’s a small wood stove and a direct vent propane heater,” says Jim Bannon, owner of Village Green Timber Frames. “Either one easily heats the building. The wood stove is for day-to-day use, since the radiant heat it offers is so pleasant and we’ll have wood forever if we take care of our forests." The propane heater provides a backup and satisfies bank lending requirements. It also provides frost protection if the homeowner is away in winter for an extended period, though experience has shown that the building almost never drops below 40 degrees even without heat. “I don’t know if the house would ever drop below freezing,” Bannon says. I was working on finishing it in January when temperatures were dropping below zero at night and the lowest it got inside was 38, and I still hadn’t put in the weatherstripping on the doors or upstairs windows.”
Aside from energy efficiency, the major elements of the ecological house are natural, local materials; modest size; and construction meant to last centuries, rather than decades.
The heart of the building is the timber frame. “This is a building technology that has proven itself over a very long time period,” says Bannon, who has been building and restoring timber frames since 2003. “Europe is full of timber buildings that are 500 years old. The structural soundness of these building is unsurpassed by any other type of wooden construction. Of course for a building to last 500 years, people across the generations have to love it and care for it. These buildings have lasted through every change of fashion since the Middle Ages. That tells you something about their enduring appeal. I think people respond naturally to the strength and beauty of the large timbers and visible joinery. Seeing the posts and beams right there in front of you, there’s no doubt that your house is solid.” This longevity is central to building ecologically. “Building is an inherently energy- and resource-intensive undertaking. If a building can last for centuries, instead of needing to be replaced after 75 or 100 years, think of the pressure that takes off our forests and other resources.”
The timber frame walls and roof are built out with a lightweight truss system. The 9-inch walls and 12-inch roof cavity are filled with dense-pack cellulose insulation, made from recycled newsprint. “Here’s one of the keys to our energy efficiency,” says Bannon. “The truss system allows us to get very high insulation values – R-38 for the walls and R-47 for the roof. Since our trusses eliminate almost all thermal breaks, the difference with an R-19 stud-built wall is actually even better than it appears.”
While the insulation keeps the heat in, the earthen floor -- also known as poured adobe -- stores it in its large mass and releases it slowly at night. The floor is a traditional recipe that mixes clay, gravel and straw. Common in other parts of the world, earthen floors have been gaining in appeal in the U.S. over the past decade or two as the natural building movement has gathered momentum. Bannon says it’s the floor that everyone who sees the inside of the building wants to know about. “It looks different than anything they’ve ever seen – dark earth with lots of chopped straw visible. It resembles polished leather more than anything, but the best thing about it is how it feels underfoot. Softer than concrete, stone and tile, it is still hard to the touch, but feels soft when you walk on it. I don’t really understand it myself,” admits the builder. “When you walk on it, somehow if feels like it’s molding itself to your feet.”
Like the floor, the wall finishes are traditional too, mixing clay and lime with fine sand and chopped straw. “The clay and lime are great at moderating interior moisture,” says Bannon. "And the natural plaster has a subtlety and warmth that you just can’t get from sheetrock and paint. In fact, we dropped our original plan to apply a coat of limewash as a finish when we saw the soft creamy white of the dried plaster itself. It needs nothing else." In keeping with the emphasis on local, natural materials, Maine spruce was used for the ceilings and Vermont slate for the mudroom and bathroom floors. “To keep costs down and use all the materials at our disposal, I milled leftover timbers to make the cabinetry and stair rails,” says the builder. “We ended up with almost no waste from the building. There was no dumpster on the site. We took a few bags of trash to the transfer station. The leftover scraps of wood, maybe a quarter cord’s worth, went into the woodstove.
“We’re getting there’” says Bannon of building ecologically. “My vision is to build a house that will last 500 years with almost no maintenance and that will compost back into the land at the end of its useful life. No concrete, no plywood glues, no petroleum products. Just wood, stone, earth and straw. And a pile of nails after the rest is gone. But those can be picked up by some future carpenter with a hammer, a set of house plans, and big dreams,” the builder says with a grin.
Village Green Timber Frames can be reached at 374-5722 during business hours.