building code changes that take effect on January 1, 2012 in Ontario and are already in effect in British Columbia. Constructing houses to E80 standards is intended to be a big interim step towards the ultimate destination of all new homes eventually being built to an E100 level. E80 homes consume about 30% less energy than new homes built to current code standards. But whether or not the new home you buy next year delivers this level of performance isn’t guaranteed. That’s because there are various kinds of E80-based homes allowed on the market.

• Houses built following the so-called “prescriptive” and “performance” paths are made using a certain recipe list of materials, assuming certain levels of air leakage, but with no actual testing done after construction to prove the E80 standard was actually achieved. And field studies show that the diligence of building crews has a huge impact on the air tightness of new home all built using the same methods.
• By contrast, homes built to E80 standards that include blower door field testing are individually verified to deliver actual energy gains.

Another thing to realize is that the EnerGuide for New Houses scale is logarithmic, which means the higher you go on the scale, the larger the difference there is between two numbers. An E80 home uses 50% less energy than a E67 home, for instance. Moving further up the scale, an E86 structure saves an additional 50% over the E80 rating.