Like many other owner/builders planning an energy-efficient home, RedFalcon6 is well aware that careful air-sealing is considered a cornerstone of high-performance building. But do the numbers really add up?
“I have to confess,” RedFalcon writes in a recent Q&A post, “I’ve never sat down and done ‘the math’ on the payback for increasing airtightness from ‘OK’ to ‘Pretty Good’ to ‘Awesome.'”
All else being equal, RedFalcon asks, what’s the financial value of reducing air leakage by two thirds—from 3 air changes per hour at 50 pascals of pressure (3ACH50) to 1ACH50?
RedFalcon points to a 2013 California study by the Lawrence Berkeley National Laboratory that suggests the financial return isn’t dramatic. Researchers found that the average value for a California home where leaks had been reduced to Passive House levels (0.6ACH50) amounted to about 2000 kwh of electricity per year.
“So going all the way to passive standards only saves an incremental $200 bucks on an average home?” RedFalcon asks. “Seems not worth it!”
“Prove me wrong!” he adds. “Am I an idiot or just misreading this study?”
Is airtightness worth as much as it’s cracked up to be? Or, as the title of RedFalcon’s query asks, is this revered benchmark “…mostly BS”? That’s the topic for this Q&A Spotlight.
It depends on where you live
Several GBA readers say the answer depends in part on where you live—not only from a climate perspective, but also taking the local cost of energy into account.
Russell Miller, for example, says he is a builder in a poor state where energy costs are not a burden, at least not now.
“I build for a living,” he says, “and I can state for a fact, it’s hard to justify extreme insulation and airtightness to…