SASKATOON'S SUPERINSULATED HOUSE

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As already noted, the ceiling of a superin-sulated home receives its own wrap of polyethylene, above which R-60 insulation is installed. In order to keep the vapor barrier unbroken, builders like to rely on exterior hatches for attic access, and avoid installing recessed ceiling-mounted light fixtures. The basement, too, is insulated—to a minimum of R-20—and also has its own vapor barrier.

HOW THEY PERFORM
The happy result of all this careful attention to minimizing heat loss and air leakage is that the Energy Showcase homes use about 75% less fuel for heating than do even those houses that were previously considered to represent the state of the art in energy efficiency. For example, during one ten-month period, the total heating bills for the Saskatoon residences ranged between $59 and $143 . . . that is, from $6.00 to $ 15.00 a month per household.

Most builders chose to install gas furnaces (in Canada, natural gas costs about $2.30/1,000 cubic feet ... as compared to an average of $4.50/1,000 in the U.S.). They've since discovered, though, that even the smallest units (rated at around 50,000 BTU/hour) produce far too much heat for the airtight dwellings. One of the Showcase homes actually uses its domestic water heater, equipped with a circulating coil and forced-air blower, to provide all of its warmth. And the owners say their total gas bill—for hot water and home heating—averages $10 to $15 a month.

For the past 13 months, the Energy Research Group of the Department of Mechanical Engineering of the University of Saskatoon has extensively monitored the energy consumption of all the homes. Every 15 minutes a computer records information on electricity and gas consumption, the temperature inside each house, and external weather conditions. In addition, Canada's National Research Council has monitored one home that has been left vacant for a year, conducting tests with simple electric space heaters and infiltration studies using tracer gas.

When the monitoring is finished and the data are evaluated, researchers should be able to pinpoint the precise design features (and flaws) that have the greatest bearing on a low-energy structure's performance.

On the whole, though, all 14 houses have proved more than satisfactory. Their wintertime energy consumption is dramatically low, and there've been no serious overheating problems in the warmer months. (Although Saskatoon's winters are savage, the summer daytime temperatures average above 70 °F.) Builders believe the minor overheating problems that have cropped up can be corrected by adding more overhang or installing shutters to limit summertime solar gain.

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