A Zero-Energy Community: Part 2
Project Manager Brad Liljequist chronicles the building of the zHome, a ten-unit townhome in Issaquah, Washington—the first multifamily zero-energy community in the United States. Part 2: Building REALLY green... It's easier than you think.
Forty percent. That’s the share of total CO2 emissions each year in the US that comes from energy used in buildings. Building operations—heating, cooling, lighting, and everything else inside the walls—are the single largest generator of carbon dioxide in the country. It’s an easy thing to forget about, sort of like background noise. But it’s there, humming along, 24/7.
One of the core environmental benchmarks of zHome is achieving zero net energy and zero net carbon emissions. We are achieving this with a number of conservation technologies which reduce energy use by about two-thirds of that of a typical townhome. We then offset the remaining third with solar panels mounted on each zHome roof. The extra energy these panels generate during the summer will offset the amount of supplemental energy the units will need during the cold, dark Northwest winters.
Figuring out how to get to zero net energy and zero net carbon emissions at a cost accessible to the mainstream market was not an easy task. A subgroup of our design team wood-sheded for many hours in a series of meetings at the David Vandervort offices. The stars of the show were Tom Marseille, WSP Flack and Kurtz managing principal, energy expert, and Cascadia Green Building Council board member, and Chuck Murray, then of the WSU Energy Program and now with the State of Washington Department of Commerce, where he leads updates to the State Energy Code.
The design that emerged through those hours combined two core conservation strategies that cut our energy use in a one-two punch: thick, highly insulated, very tightly sealed walls (R-38 walls and R-63 ceiling for you techies), and a ground source heat pump system that is three times more energy efficient than the best forced air furnace.
A sprinkling of other things round out the picture, including 100% LED and fluorescent lighting, in-home energy monitors, heat recovery ventilators, super efficient appliances, hydronic in-floor heat distribution, and natural daylighting. And then of course the solar panel production completes the package.