Sunday, September 15, 2013

Performance Home, Part 2

Picture a hole in the side of your house that’s just as a big as a typical computer screen. Imagine the wind blowing through that hole. The hole is real. If you were to combine all the cracks and crannies in a typical Canadian home, they’d add up to almost 1,400 square centimetres, roughly the size of 2.5 magazine pages.

Plugging that hole is the simplest way for Canada to save energy. Plugging the hole also saves money, creates jobs, cuts greenhouse-gas emissions and makes our homes more comfortable.
We know how to find the hole. Canadians pioneered the use of a tool that can measure the airtightness of a building. Natural Resources Canada (NRCan) has used this “blower door” to test more than 800,000 Canadian homes.
Canadians also know how to fix the hole. Way back in 1977, they built a house so airtight and so well insulated that a hair dryer could have kept it warm through the winter – in cold Saskatchewan.

Yet despite the fact that buildings account for roughly one-third of our national energy consumption and the fact that we’re world leaders in small building energy-conservation technology, Canadians still haven’t plugged the hole. Most of our existing homes remain quite drafty, and most of our new homes fail to meet decades-old efficiency standards.

Builders have long known that heat claims the lion’s share of the energy consumed in Canadian homes: 57% of the total, compared with 24% for hot water, 13% for appliances and 5% for lighting. They’ve also known that heat escapes wherever air escapes, mostly under doors and around windows.
A standard measurement agreed upon is: the number of times per hour the blowerdoor fan would suck all the air out of a house at a prescribed pressure of 50 pascals (Pa). The metric is called “air changes per hour (ACH)” at 50 Pa. With gaps totaling 1,400 sq. cm, the average Canadian home leaks enough air to result in 6.85 ACH@50Pa.

In the wake of the 1973 Arab oil embargo, the Saskatchewan Research Council designed an energy-efficient home appropriate for the Saskatchewan winter. The oil crisis prompted many similar projects, with most focusing on new ways to trap solar heat within a more or less standard building. The Saskatchewan team elected, instead, to design a radically more efficient building envelope. The Saskatchewan Conservation House, completed in Regina in 1977, was likely one of the first buildings to combine three key elements: superinsulation, extreme airtightness and a heat-recovery ventilator.
In an era when nearly all houses were constructed of four-inch-thick walls filled with R-8 insulation, the two-storey Saskatchewan house featured 12-inch-thick R-40 walls and R-60 roof insulation. Likewise, single-paned windows were then the norm; this home had triple-glazed windows. The house also boasted extreme airtightness. Most new houses at the time scored in the range of 9 ACH@50Pa; the SCH achieved 0.8 ACH@50Pa. At the time it was likely the tightest house in the world.
To provide fresh air to the airtight house, the Saskatchewan team built an air-to-air heat exchanger. This device pulled in fresh (but cold) outdoor air through a series of baffles. Stale (but warm) indoor air was pushed out through the other side of those same baffles, and heat was transferred from the exhaust air to the incoming fresh air.
The SCH had no furnace. Instead, it relied on a system that collected solar heat during the day, stored it in a water tank, then released the heat at night. All told, the house required less than a quarter of the energy consumed by a standard home of the time.

That same year, the “House As a System” approach pioneered in Saskatchewan formed the basis for a new national building standard that required R-20 insulation, blower-door test results of 1.5 ACH@50Pa or better, the installation of a heat-recovery ventilator and the use of non-toxic materials. The new standard became a partnership between NRCan and the Canadian Home Builders’ Association. It was the toughest standard in the world at that time and presaged by decades the advent of green building initiatives such as BuiltGreen or LEED (Leadership in Energy and Environmental Design). The new standard was voluntary, but its authors intended for its gradual integration into the national building code. With their sights set on plugging the hole in Canadian homes by the turn of the century, they named the new standard “R-2000.”

The above content is mostly a shortened re-print of the article High-Performance Homes - Why isn't Canada spearheading the movement to build more sustainable homes? published in June 2012 issue of Canadian Geographic.

No comments:

Post a Comment