Video: LEED Platinum Habitat for Humanity House in Westford, Mass.
BY DANIEL MORRISON
THE MOST AFFORDABLE LEED PLATINUM IN THE USA?
We often hear that green building is only for the wealthy. Building Science Corporation, the architecture and engineering firm that designed this Habitat for Humanity house, begs to differ. They think that the people who need the highest-performance homes are the ones who can only bear the lowest operating costs: energy, water, and maintenance bills. It does not help to get first-time affordable-home buyers into houses they cannot afford to KEEP. Affordability is as much about operating costs as it is about first costs.
Affordable houses need to be affordable tomorrow, too
To be truly affordable, a house needs to be built thinking about the economics of 20, 50, or 100 years out. With an R-20 foundation, R-40 walls, and an R-60 roof, Building Science Corporation has put their dollars to highest use in this home by keeping the design straightforward and simple and by paying as much attention to insulation details as to details about moisture management.
What makes a house green?
"At Building Science Corporation, we think that what makes a house green is a house that provides long-term durability, long-term energy efficiency, and provides a healthy indoor environment," says company president Betsy Pettit, FAIA. The house featured here is on track to attain a LEED Platinum rating without using renewable energy features such as photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. panels or wind generation, "hopefully making this the most affordable LEED Platinum house in the country," says Pettit. Building Science Corporation achieves such high-energy performance—without adding renewable energy—by using a carefully detailed thermal envelope. And that's where the aforementioned R-20, R-40, and R-60 come in. These values are significantly higher than what you'll find in a normal New England house, and about 50% higher than the International Energy Conservation Code specifies.
Connecting the parts is as important as thick insulation
Four inches of polyisocyanurate on the exterior walls and roof and 2 inches in the basement get the R-values up, but it's the connections between foundation, floor, walls, and roof that keep the heat in.
With tight construction and a thermal envelope that follows the exterior shell of the home, ductwork will be placed inside the conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. , which will let the HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. system work more efficiently.
The Building Science Corporation approach to high-performance building is to employ systems-thinking from the minute pencil hits paper right through to windows being flashed and siding installed.
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