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NRC Highlights, 2009-06-01
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Building better houses under the Midnight Sun
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ARCHIVED – Building better houses under the Midnight Sun
June 01, 2009— Ottawa, Ontario
Making houses inside the Arctic Circle more durable and energy-efficient holds challenges — some less obvious than others. Southern Canadians know that winters there are cold and deep. Fewer may understand the roles that a short but intense summer's heat and
accelerated ultraviolet damage play under the 24-hour-a-day "midnight sun" made famous by poet Robert W. Service.
Less poetic, but just as important, are a brief construction season, housing shortages, a scarcity of qualified construction tradespeople and extremely costly shipping for materials. All of these factors complicate the job of building high performance houses up north.
On-site consultation and data gathering in communities such as Arviat Nu helped NRC-IRC researchers define highly energy-efficient construction methods for building envelopes in the Arctic.
Yet a growing population "North of 60" needs more homes — homes that are affordable and energy-efficient. And research into very innovative, energy-efficient and durable buildings can help local people address these issues, says Madeleine Rousseau of the NRC Institute for Research in Construction (NRC-IRC) in Ottawa.
Supported by Natural Resources Canada, the Canada Mortgage and Housing Corporation, the Panel for Energy Research and Development and NRC, Rousseau's research team has focused for four years on the heat, air and moisture performance of Canadian Arctic housing.
Along the way, the team has published literature reviews of building envelopes in Canada and other Nordic countries, and of climatic severity at many Nordic locations. It has also done field surveys in the Yukon and Northwest Territories carrying out energy audits and
measurements of temperatures and relative humidity levels inside homes.
Rousseau says she expected at first that high occupancy and low air exchange rates would cause fairly humid indoor air. In fact, the Arctic homes she surveyed leaked a lot of cold air, which often made indoor air quite dry and interior surfaces very cold. This often caused frost build up and related water damage on the inside face of the walls.
By consulting with housing communities in Whitehorse, Yellowknife and Arviat, the NRC team got a strong sense of what drives decisions regarding which technologies are typically used on new housing projects. This helped the team choose which types of wall assemblies to lab-test.
The researchers found that northern conditions drove conscious trade-offs. Builders opted for "keep-it-simple" construction methods that can be implemented on-site with limited training and that allow the construction crews to close-in the envelope quickly. High shipping costs also discourage elaborate building methods such as double wall systems, which require extra materials, even though they might be more energy-efficient over the service life of the houses. Builders tended to use typical two-by-six wood frame walls, close them on the outside, then insulate from the inside to give a high R-value and ensure the airtightness of the envelope.
Based on these findings, the team returned to Ottawa with five promising new wall
assemblies to test in the NRC-IRC Envelope Environmental Exposure Facility (EEEF). EEEF is a large climate chamber, where sections of full-scale test walls can be exposed on one side to outdoor weather of -40° C with strong winds, and on the other to normal indoor
temperatures, humidity and pressures — to understand their performance.
Computer modelling based on the tests will allow researchers to try out further "what if" scenarios by plugging different indoor and outdoor climate changes into the model. Although the NRC research focused at first on Nordic communities' extreme conditions, interest in very high energy-efficiency building methods is increasing elsewhere, says Rousseau.
"The work that we initially thought would be of most benefit in the North — going for very high performance and a lot of insulation — is now gaining interest in the South, because of high energy costs, concern for environmental sustainability and climate change mitigation," she says. "The findings of this study may well have a broader potential impact on the building community."
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