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The Great Ventilation Debate – Live at Affordable Comfort!

Great Ventilation Debate Ashrae 62.2 Panel Aci Conference

Last week at the Affordable Comfort Conference (also known as ACI), I co-moderated a panel called The Great Ventilation Standard Debate.1 Duncan Prahl of Ibacos proposed the session and rounded up a collection of some of best building science folks in North America to be on the panel. And if you’ve been paying attention to this blog, you know who one of them was.

Last week at the Affordable Comfort Conference (also known as ACI), I co-moderated a panel called The Great Ventilation Standard Debate.1 Duncan Prahl of Ibacos proposed the session and rounded up a collection of some of best building science folks in North America to be on the panel. And if you’ve been paying attention to this blog, you know who one of them was.

The photo above (taken by Nate Adams) shows the cast of experts on the panel. From left to right, they are Joseph Lstiburek, PhD, PE, Iain Walker, PhD, Paul Francisco, Michael Lubliner, Rick Karg, and Don Stevens. All but Lstiburek are on the ASHRAE 62.2 committee. In addition, there were 3 or 4 other members of the 62.2 committee in the audience.

And speaking of the audience, we had a great crowd. I haven’t heard an official number, but it was probably 150 to 200. The photo below (taken by Bethany Profaizer) gives you a view from the back.

A brief history of the debate

I’ve written about the issue of mechanical ventilation and the ongoing debate several times over the past year and a half. Here’s the short version, with links to the articles I’ve written.

First, everyone agrees that airtight houses need mechanical ventilation. (Also not up for debate is that homes need to be airtight. A house does NOT need to breathe.) Since we agree that ventilation is necessary in airtight homes, we need some guidance on how to do that. “Build tight; ventilate right” is a great mantra, but that second part needs to be fleshed out.

That’s where ASHRAE comes in. They’ve got a ventilation standard for homes, and it’s gone through several updates since the 1989 version. Since 2003, it’s been called ASHRAE 62.2: Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings. The standard covers a lot of ground, but at the heart of it is a method for determining the amount of ventilation air a home needs. And that’s where the debate begins.

Joseph Lstiburek, PhD, PE, has argued loudly against the way that rate is determined. His biggest complaints about 62.2 are that:

So Joe introduced his own standard last year – BSC-01. (It’s really more of a set of guidelines than a standard, though, because it hasn’t gone through a consensus process like 62.2 has.) BSC-01 is for new homes only and allows systems that are balanced, that distribute the air throughout the house, and that mix the air to run at lower rates.

The opening  punches

We opened the panel discussion by asking each of the six panelists to introduce themselves and make an opening statement. The five 62.2 members were diplomatic in their words. Lstiburek opened by saying that 62.2 isn’t based on science, costs people money they don’t need to spend, and makes homes too dry in cold climates and too humid in humid climates. Further, he said, it’s worthless because no one is adopting it.

great ventilation debate ashrae 62.2 aci affordable comfort conference cropped

The discussion was civil throughout, although there were some pointed disagreements. Francisco talked about the justification for the rates and opened his comments by saying, “ASHRAE 62.2 is wrong 99% of the time for most homes.” He said the purpose of the standard is to recommend ventilation strategies that can do the most good for the most homes.

Francisco (or was it Walker?) referred to a study from Scandinavia that would justify even higher rates than we’re using now. Lstiburek jumped in at that point and said that study was wrong and the real takeaway from it wasn’t that we need higher rates but that we need to fix moisture problems before they become indoor air quality problems.

Rick Karg asked Lstiburek a few questions at one point in the discussion, one of which was, If you’re criticizing 62.2 rates for not being supported by the science, what science supports the rates you recommend? It was an excellent question, and Lstiburek’s answer seemed incomplete to me. “We know from experience that the higher rates lead to problems – we do not have such problems with the lower rates,” he said, referring to his experience with hundreds of thousands of homes built in the Environments for Living and Building America programs in the ’90s.

I say his answer felt incomplete to me because he didn’t address the health issue. How I think he should have responded is that since there’s no health science to support either 62.2 or BSC-01 rates, we should do what causes the fewest problems and has the greatest chance of not being turned off by the occupants.

A serious problem with exhaust-only ventilation

The debate didn’t focus as much on the problems with exhaust-only ventilation as I thought it would, but Lstiburek did make a compelling point on that issue. In multifamily buildings, using bath fans and the kitchen range hood to satisfy 62.2 is nearly impossible to do effectively. “If the building is compartmentalized,” Lstiburek said, “good luck with makeup air. What are you going to do? Leave a window out?” The problem can be especially severe for inside units, which might have only one wall to the outside.

Hope for the future of 62.2

Francisco had the best line of the day. We asked the panelists all to make a closing statement and tell us where they see things going. When it was his turn, Francisco began, “I don’t know where we’re going, but I do know how we got in this handbasket.”

The debate at ACI was lively and interesting yet friendly. Lstiburek was laughing with Walker over private comments at one point, and the group found some things to agree about. The biggest point of agreement was that kitchen exhaust is really important, and we need range hoods with good capture efficiency, not just high ventilation rates. Francisco, the chair of the 62.2 committee, even called for a vote to document that agreement.

Toward the end of the discussion, Lstiburek made an announcement. “I’d like to get back on the committee, if you’ll have me,” he said. “I may have to beg and grovel, but I’d like to be a member again.”


It was a great discussion at the ACI conference by some of the most expert minds on the topic of ventilation. Both sides made good points. Both sides made bad points. We also had some great comments and questions from the audience, including one from a gentleman who works in weatherization of existing homes. When he has to add a ventilation system, he said, that means less money to improve the insulation, air-sealing, and HVAC system.

As he wrapped up the discussion, Duncan Prahl reminded everyone that the ASHRAE 62.2 committee members are all volunteers and that anyone can contribute to the evolution of the standard. It’s easy to criticize something you don’t like. It’s harder to get involved and make it better. My sense after this discussion is that the 62.2 standard is about to take the next steps forward and address some of the issues that led Lstiburek to go rogue last year.


Related Articles

Lstiburek Has New Ventilation Standard—Resistance May Not Be Futile

Can Occupants Be Trusted to Control Their Home’s Ventilation System?

Interview with Dr. Joe Lstiburek — The Ventilation Debate Continues

ASHRAE 62.2 Committee Chair Predicts Confusion & Frustration from BSC-01 (interview with Paul Francisco)

The Ventilation Debate Continues: Interview with Dr. Iain Walker


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1. Our proposed session title was The Ventilation Standard Debate – Real Housewives of 62.2, but the folks at ACI, probably wisely, chopped off the last bit and gave it the less incendiary title.

This Post Has 10 Comments

  1. 62.2 and M1503.4, Kitchen
    62.2 and M1503.4, Kitchen Make-up Air, have the same issues, as far as I’m concerned. You cannot tell me that the same amount of dry and cold air should be brought into a house in Wisconsin or New England as it does in dry El Paso or humid New Orleans. ICC, ASHRAE and Industry practitioners must address common sense solutions to these problems. I wonder if all those PhDs get in the way of thinking… ha!

  2. Until we have better methods
    Until we have better methods we’re not going to be able to have a true standard. The standards are based on assumptions about building conditions that, as Paul Francisco acknowledged, we don’t know most if the time. 
    What we need is an IAQ-CPU. A modestly priced sensor and control panel that would know the humidity, CO2, temperature and pressures inside and out. The system could vary the ventilation to compensate for the actual conditions. It should know if the HVAC system is operating, if a (shower, range, washer, dryer etc.) is running. I’m sure there are other parameters that might be helpful, but I’m not currently designing the system 😉 
    A system like that might get us to where we are only wrong 50% of the time. Eventually even that might improve. 
    We have all the parts we would need off the shelf. We’d need to reduce cost and make an integrated package that is EASY TO INSTALL AND USE. A reasonably priced module that promises better IAQ sounds like an easy sell in upscale homes, initially. It should then work it’s way into other segments of the market as people get used to the idea. 
    Does such a thing exist? Any manufactures got a glimmer in the eye? 
    Unless we know the actual conditions we’re ventilating for we are going to be wrong most of the time.

  3. Allison, great job moderating
    Allison, great job moderating. This was a great panel and it was the one I was waiting for all week. What a great group of experts in one place. I appreciated Rick Karg reminding everyone that moisture is not the only pollutant/issue we are addressing with ventilation. I know I get hung up on that issue. Pollutant isolation and filtration are two issues I am now pursuing more info and direction on as I continue to make recommendations for healthy indoor air quality.

  4. Thanks for the recap… wish
    Thanks for the recap… wish I could been there. I just read Mike Rogers’ ACI wrapup, where he quoted Paul Francisco as saying that the 2013 standard wasn’t quite ready, but they released it because it was due to be released. Wow.  
    Yes, 63.2 needs some work. Maybe they’ll accept Joe back.

  5. Great Post Allison as usual.
    Great Post Allison as usual. I think one question I would like asked is should there be regional rules for ventilation? Does the same strategy in Northern Plains state make sense in the Deep South. Should San Diego and Saratoga Springs FL have the same measures and methods of ventilation?

  6. “In a high-rise building
    “In a high-rise building that’s not compartmentalized well, units at the top can experience a positive pressure from the stack effect.” 
    Fine, but 62.2 is for low-rise not high rise buildings.  
    On another note — what are people’s thoughts about “vent-free” appliances? Standard 62.2 can now address these.

  7. Sidebar comment: Interesting
    Sidebar comment: Interesting factoid from a recent local news source – most of the counties in my locale (SouthCentral PA) received an unsatisfactory air quality rating by the EPA. Most notorious pollutant – ozone. 
    All the ventilation standards to date assume that outside air is better than inside air. No science to back this up either.

  8. Armando:
    Armando: Based on what I heard there, I think you’ll see them beginning to address this issue. 
    Charles: Yeah, I’m not crazy about the exhaust-only ventilation strategy myself. 
    Bill S.: True, but do we really need to add that level of complexity to homes? 
    Steve: Yes, and as Amy Musser wrote recently, we probably shouldn’t think of water vapor as a pollutant at all. 
    David B.: Yep. He really did say that. 
    Shawna H.: Sorry you missed it. It was a good one. Nice to meet you while you were there, though! 
    Glen G.: Indeed! That was a point made during the debate, and one that I think ASHRAE is beginning to address. 
    John P.: Oops. You’re right, of course. And the blame for that goes to me, not Joe. I extrapolated from what he actually said to the high-rise case. I’ve edited the article to remove that bit. 
    And yes, ventless/vent-free/unvented/room-vented/lung-vented appliances should definitely be addressed by 62.2, in my opinion. We discussed that a little bit in my interview with Paul Francisco last year. 
    David E.: Yes, outdoor air quality is certainly a critical factor in ventilating homes. We discussed that a little bit in my interview with Iain Walker earlier this year.

  9. We just had a building
    We just had a building inspector tell us to disconnect the continuous run operation on the bathfans in a multifamily project because he does not want the negative pressure in the units that this ventilation strategy will create. Which of course now leaves us scrambling with how to meet our ventilation requirements for LEED & Energy Star V3.

  10. Excellent discussion. Any
    Excellent discussion. Any chance of showing this as a webinar?

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