Cold Snap Tests High-Performance Homes
At the top of a hill in the Old Port section of Portland, Maine, stands a city landmark: the “Time and Temperature Building.” On the roof of the building is a lighted sign displaying — yes — the time and the temperature, alternating with a sponsor’s message: “Call Joe.”
But you don’t need Joe to tell you it’s cold in Maine. Last week, the sign’s message at dawn, flashing across the waters of the Portland harbor to island communities off shore, has been nothing if not consistent:0°F.
For some New Englanders—and for homeowners in the nation’s breadbasket as well—the winter cold snap has brought discomfort, along with worries about the supply and price of heating fuel. But what about the fortunate few who live in high-performance modern houses? Are those buildings living up to their promise in the face of lingering polar air?
In December, JLC featured four advanced high-performance, super-insulated building designs. This week, we talked with homeowners who are living in some houses built following those designs to find out how the homes are coping with this year’s record cold.
Wood heat only in Vermont
In Ripton, Vermont, homeowner Chris Pike is living in a house constructed by builder Alex Carver and designed by Belfast, Maine, builder Chris Corson. Aside from a few tweaks—a change in the second-story floor plan and a longer shed addition on the north side—the house is a near replica of the home Corson built in Knox, Maine, featured in the May and June, 2012, issues of the Journal of Light Construction (see “An Affordable Passive House — Part 1,” and “An Affordable Passive House Part II“). But Chris Pike’s house has the more advanced details described in the JLC feature from December 2013, “Building Above-Code Walls” (subscription required), including a breathable synthetic exterior membrane in place of the fiberboard sheathing used in the earlier example.
Chris Pike’s house, built by Alex Carver (Northern Timbers Construction), near completion in fall 2013. This winter, says Pike, the house stays comfortable in below-zero weather with one or two firings of the wood stove per day.
Like the Knox house, Corson’s earliest Passive House prototype, the Ripton house is designed to be heated with a single, wall-mounted Mitsubishi Mr. Slim air-source heat pump that draws 1800 watts and is rated to supply 12,000 Btu/hr. But that output is under ideal laboratory conditions, not in below-zero degree weather. As it turns out, however, the Pike family isn’t using the heat pump. “It got turned on once, when the house was commissioned,” says Chris Pike.
Instead, the Pikes are relying on the home’s wood stove, a Morso 3112 rated at 30,000 Btu/hr. They light one or two fires a day. “In the evening, my wife might start a small fire in the wood stove after the kids are in bed, just for us to hang out by,” says Chris Pike. “And by ten or eleven o’clock the fire goes out and we go to bed. And if it’s around 68 degrees when we go to bed, when we get up in the morning, it’s usually around 62 or 64. And if it’s going to be a sunny day, it’s best not to start the wood stove again in the morning, because the sun will heat the house up. Even on these days where it has been 10°F or 5°F outside, the sun brings this place right up to temperature.”
“Today,” said Pike, “it’s sunny and it’s 10°F outside. It’s 72°F in the house right now at one in the afternoon, and the wood stove was out by 9 o’clock this morning. On days like today where it’s bright and sunny, it’s almost overkill to have run the wood stove in the morning.” With January almost over, Pike says, the family has burned a third of a cord of wood this winter. “We’re burning hot fires, and then let them go out,” he says. “I’ve had to empty the ash can maybe twice for this thing, because we just burn so efficiently that there is not a lot of ash left over.”
The coldest weather Pike has seen this winter is 20-below-zero one night. The house took it in stride, he says. “We might run the stove a little more in the evening. We might start it at six instead of eight. But it still goes out—we don’t run it all night long. And when we get up in the morning, it’s still around 62 to 64 degrees.
Bedrooms on the north side of the house run slightly cooler than the sunnier south-facing rooms, Pike notes, but they’re still comfortable. “We leave the doors open, and it evens out,” he says. “I’m walking around in shorts and a T-shirt, because it’s 72 or 73 degrees in here with no heat on.” Bottom line, says Pike: “The house has worked great. I can’t be happier. I can’t say enough about it. It’s doing everything it’s supposed to be doing.”
Read the rest of the article: http://www.jlconline.com/passive-design/cold-snap-tests-high-performance-homes_o.aspx