It’s been a while since I’ve written about what I had been calling “The Great Ventilation Debate” back when Joe Lstiburek was battling the ASHRAE 62.2 residential ventilation committee. The 62.2 committee meets in person twice a year at the two ASHRAE conferences, and they just met last Friday and Saturday in Houston, Texas.
A few things have happened over the past few years, so let me give you a brief update.
Back in 2013 when Dr. Lstiburek introduced what he called his ventilation standard, BSC-01, the 62.2 committee had just removed the default infiltration credit for homes, which resulted in higher ventilation for most new homes that had to meet strict airtightness codes. Lstiburek’s rates were based on the 2010 version of the 62.2 standard, with credits for reducing the rates further for ventilation systems that were balanced, distributed, and mixed.
After the big debate at the 2014 Affordable Comfort conference in Detroit, Lstiburek rejoined the 62.2 committee. In 2015, they had proposals to adopt something very similar to BSC-01, but they didn’t pass. The following year, a new proposal to lower the ventilation rates (but not as much) in the 62.2 standard was voted on, and it, too, failed.
So the rates specified in the 62.2 standard are pretty much the same as they’ve been since the 2013 version of the standard dropped the default infiltration credit. A home needs 7.5 cfm per person (with number of people defined as number of bedrooms plus one) and 3 cfm per 100 square feet of conditioned floor area. That’s the total. The amount you have to add can be less if you do a blower door test and take the infiltration credit (not to be confused with the default infiltration credit mentioned above).
Ventilation in the International Residential Code