- 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.