Another Report on the Great Ventilation Rate Debate
A clear winner emerged at the ventilation debate held at the recent Affordable Comfort conference in Detroit
Here is my rundown of the recent Affordable Comfort (ACI) conference in Detroit.
It was great to catch up with — or at least brush by — longtime industry friends, in the case of Allison Bailes of Energy Vanguard and Andy Frank of Sealed. It’s really cool that the industry is small enough you can become friends with even the big names.
For anyone considering going to ACI, it is worth it for the networking alone. Last year I had dinner with Chris Dorsi, one of the authors of my energy auditor textbook. I just asked if he was hungry. He was. So we ate. Try the same thing.
A contentious, one-sided debate
Allison Bailes of Energy Vanguard recently wrote a post on the Great Ventilation Debate. I thought he was very diplomatic about it, but I felt that the debate was actually more contentious and one-sided than he said.
For the uninitiated, ASHRAE 62.2A standard for residential mechanical ventilation systems established by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Among other requirements, the standard requires a home to have a mechanical ventilation system capable of ventilating at a rate of 1 cfm for every 100 square feet of occupiable space plus 7.5 cfm per occupant.-2013 is a new ventilation standard that requires generally higher ventilation levels for new homes. In other words, there must constantly be a fair amount of airflow out of (and consequently into) a home to provide continuous fresh air.
A committee of volunteers (poor guys, they really got shot at) designed the new standard, but Dr. Joe Lstiburek of Building Science Corporation strenuously disagreed with their findings. At several junctions, Joe looked so mad he could spit. I saw three main thrusts of his argument.
Too much moisture during the summer
First, much of his criticisms was based on the idea that the new standard required so much airflow that in hot humid climates too much moist outside air would be brought in in summer and in cold climates too much dry winter air would be brought in — decreasing comfort and increasing energy costs for both examples.
The point of the new, generally higher flow standard is to dilute bad stuff in houses like volatile organic compounds, carbon monoxide, and other contaminants. Joe posited that there are no epidemiological studies that show these things are actually bad for us, yet we know that the moisture problems described above are indeed a problem. So we are adjusting to fix something we aren’t sure of to the nearly guaranteed detriment of what we are sure of.
Balanced systems work better than exhaust-only systems
Second, there was the argument about balancing exhaust and supply air flows. Dr. Joe has come up with his own competing “standard” — one that gives more leeway to balanced systems that purposely allow for intake and exhaust in equal quantities (suck and blow in Joe-speak). The ASHRAE 62.2-2013 standard doesn't treat balanced systems differently from exhaust-only (suck) systems.
I agree with Joe wholeheartedly on this. If you only provide for exhaust, where does the makeup air come from? Probably lousy places like basements, crawlspaces, and attics. The committee was trying to reduce costs here, but an alternative path requiring less ventilation for balanced systems would be good.
Politics or science?
Third, the standards were largely politically motivated, not based on sound science.
In my humble opinion, Dr. Joe landed by far the most punches in the debate. The only good hit back from the 62.2 committee was when Rick Karg of Residential Energy Dynamics asked Joe where his epidemiological evidence was. Joe did not have a direct answer to that. He did cite the experience in Canada where their ventilation standards, which are similar to the old standards, have not seen any ill health effects after 300,000 homes at 10 cfm. An imperfect answer, but as good as we actually have.
I posted the final score as Joe 25, Audience 5, 62.2 Committee 1. It was one of the most obvious debate wins I’ve ever seen.
Nate Adams is a recovering insulation contractor turned Home Performance consultant. His company, Energy Smart Home Performance, is located in Mantua, Ohio. Using a comprehensive design approach, he fixes client woes with a market-driven process that he hopes will lead to market transformation for our industry.
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