Winnipeg Free Press - PRINT EDITION
Joist that bale
Energy-efficient straw bale homes, once a fad, are going mainstream
Your next home could be growing in a farm field.
Energy-efficient straw bale houses, once considered a fad, are going mainstream, thanks in no small part to skyrocketing heating costs.
Those that own them swear by them, contractors can't keep up with the demand, and even municipal building permit approvers, cautious by nature, have gotten with the program. Best of all, straw is a readily renewable resource.
Straw is the dry stalks of harvested wheat, barley and other cereal plants. Tightly baled and used for exterior walls, straw is a strong, non-toxic building material with great durability: Straw bale homes and churches built by wood-starved pioneers in Nebraska and the Canadian west over a century ago still stand.
And it's hard to beat straw bales' insulating value, which proponents claim has an R-value of 35 to 50, double to treble that of a conventional wall.
"It's been way cooler all summer inside our house than it's been outside," says Harry Kits, who moved into his new, 2,200-square-foot straw bale home in North Gower, just south of Ottawa, this spring.
Kits and his wife Marianne Heinen opted for straw as an environmentally friendlier way to build. Theirs is a modified straw bale design. Instead of the traditional solid straw walls, their home uses 400 bales placed on edge as infill between 14-inch deep wooden uprights roughly six feet apart.
As with any straw bale construction, Tenax, a plastic mesh, keeps the straw in place and provides a base for the lime cement plaster that covers the interior and exterior.
A breathable, silicate-based paint covers interior and exterior walls, allowing moisture to pass from the house through the straw and ensuring the bales stay dry -- no vapour barrier is necessary in straw bale construction.
The Kits-Heinen family has upped its eco-quotient by installing windows with argon and low-E coatings. A three-foot roof overhang helps shield the exterior walls from rain and keeps the hot summer sun away from the windows.
When the winter sun, lower in the sky, strikes the windows, it will warm the interior concrete floor which also contains the home's radiant heat system.
While many owners of straw-bale homes turn their construction into barn raising-style projects with friends and family supplying the labour, Kits and his wife contracted out most of their work.
They hired Camel's Back Construction (strawhomes.ca) in Madoc, Ont. to help with bale installation and plastering. Ben Polley, owner of Guelph, Ont.-based Harvest Homes, was consultant on the project.
See the home on the Ontario Straw Bale Building Coalition's province-wide tour Oct. 4 (strawbalebuilding.ca).
Polley has been designing and building straw bale homes since 2000. His website (harvesthomes.ca) offers a detailed introduction to straw bale construction. Among other things, the site mentions straw's high fire resistance and offers reassurance that neither rodents nor insects are an issue with straw bale homes.
Despite some lenders' wariness about providing mortgages on unconventional construction such as straw, Polley has seen his business increase 100 per cent every year. "The demand is far outpacing the availability of builders or designers."
Originally, most of Polley's clients went with straw and either built the house themselves or served as general contractors to reduce construction costs. Now, the majority opt for straw because of its heating and cooling benefits, and few have the time to be involved in the construction.
Many of these homes -- which cost roughly the same to build as a conventional house -- use standard heating systems like oil because they require so little energy to stay warm.
"We use R-40 as straw's insulating value when we're performing heat-load calculations, and we still find our heating systems have a tendency to be over-designed," says Polley. "We've only ever once installed air conditioning for a client, and she's never turned it on."
Ross Elliott, an Ottawa-based energy efficiency expert and owner of a small straw bale office at his home, questions whether straw has values of R-40 and above. Still, he does agree that it is a superior insulator if installed properly. Bales aren't perfectly square, so there are many hours spent stuffing loose straw into gaps.
Ottawa architect Linda Chapman, who has been designing straw bale homes for 13 years, says such intensive, costly labour makes the homes unpopular with commercial builders. She adds that because it's difficult to get the walls perfectly straight, they sometimes have a slightly lumpy, adobe-like appearance.
Chapman -- a member of the design team for Mountain Equipment Co-op's energy-efficient store on Richmond Road which includes a straw bale wall -- says that testing by Canada Mortgage and Housing Corporation and others has shown straw to be a good building material. Insurance companies will likely rate the home at the slightly more expensive log house standard. Assuming you have engineers' drawings in your application, municipal permits should not be a problem.
"The homes are generally out in the country where building inspectors have probably grown up on farms and are not scared of straw."
Canwest News Service
Republished from the Winnipeg Free Press print edition September 3, 2008 $sourceSection$sourcePage
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