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Build Tight, Ventilate Right: Lessons in Hot Air and Sticks and Stones

Venmar Enthalpy Recovery Ventilator.
Image Credit: Rob Moody, Organic Think Inc

Musings on Mazria, Lstiburek and Gifford: Part Three

I just want to set the record straight on one point: I have not imbibed the USGBC Koolaid. I do like its mission, goals, and products, and the organization has the best start of any rating system out there. As I have stated many times before, I’m a biologist by training and I am way into evolutionary biology. That’s all that needs to happen here. There are aspects of LEED that need improvement, so the USGBC simply needs to evolve in order to adapt to the changing environment: building science knowledge and feedback loops. It’s a lot like natural selection in a way. Survival of the fittest and change over time are important to businesses and businesspeople that are interested in the survival of their species.

Like I have stated before, I’m no PhD, engineer, or architect. I’d like to think that I will always be a humble student of the natural world. In that role, I’m trying to let the dissonance that exists in our industry soak in. Here’s my take on one of the bones of contention. When building, I subscribe to the mantra, “Build tight and ventilate right”. AIR SEALING!!!!! The tighter, the better, in my opinion. One hundred years ago, heating was cheap. Wood, coal, whatever—it was cheap. Not so cheap anymore. The tighter the home, the less conditioned air you lose. That’s a good thing. Not allowing for fresh-air ventilation or letting in so much unconditioned air that energy efficiency and humidity levels are compromised is a bad a bad thing. It’s a must to let in fresh air when building a supertight shell.

Let me tie this into my current thread on the banter between Lstiburek/Gifford and the USGBC. In Lstiburek’s paper, “Prioritizing Green: It’s The Energy, Stupid”, Dr. Lstiburek takes great offense to the aforementioned NBI study on energy efficiency in LEED NC buildings. I’d like to comment on one specific point that he makes in the paper:

… don’t overventilate. This idea of getting green points by increasing the rates above those specified by ASHRAE Standard 62 is just madness. Whatever happened to source control? If you don’t build stupid materials into the building, don’t do stupid things in the building, and don’t connect the interior to exterior via the parking garage, 62 works very well.

Lstiburek, an ASHRAE Fellow, is referring to LEED NC Environmental Quality Credit 2, “Increased Ventilation,” which is obtained by increasing ventilation rates by 30% over those prescribed by ASHRAE 62. Another ASHRAE Fellow, Steven Taylor, stated this in a report:

It is acknowledged that increasing ventilation rates will, in most applications and climates, increase energy use. However, the impact is relatively small, and it can be mitigated using heat recovery and other technologies. . . .The benefits of these credits are deemed to outweigh the energy impacts. Similarly, it is argued that the energy impact of increased ventilation is more than offset by the health and productivity benefits. EQ Credit 2 has been completely revised to require an increase in ventilation rates of 30% above Standard 62.1-2004 rates. The increase (and even higher rates) can be justified by recent research showing higher outdoor air rates improve occupant productivity and reduce sick building syndrome symptoms.

So how much is too much? I don’t have the answer to that. In the residential realm, in 99% of the houses that I have built, I have installed either a Venmar Constructo or a Venmar HEPA 4000, which probably provides more air changes than necessary for a home that size. Almost all of those houses are under 3,000 square feet. I know by following them over the years that the energy bills are quite low and the indoor air quality (IAQ) is quite good. A family from New Jersey moved into one of our homes with their 9-year-old son, who suffered from chronic, severe asthma. Within two months, all of his symptoms were gone. Another instance involved a family from New Mexico. The wife was chemically sensitive and wanted to seriously vet the home before they moved in. She had a variety of tests run on the IAQ of the home (including mold, VOCs and radon), and it passed all of them with flying colors. This is a tiny data set, but I know (especially since I live in one of them) that our houses work: low energy bills and good IAQ.

Unfortunately, I agree with a lot of what Gifford and Lstiburek say in their papers. What I classify as unfortunate is that you have to sift through so many condescending statements, epithets, and sardonic wit that the points get buried. In a world where (in my opinion) so many of us can’t wait for good news, can you guys try to stay constructive and positive?

I agree that we need to base the “greenness” of buildings on performance or extremely accurate models (which don’t seem to exist for all cases). I agree that overventilation can be detrimental. I agree that overglazing can negatively affect energy efficiency and comfort. I recently visited an organization’s national headquarters in Washington, D.C., a very big organization at that. It was LEED Silver—certified, but, as the tour guide admitted, the building has huge utility bills and is not performing as modeled. That part of the system needs to be fixed.

All of these things need attention, so let’s bring it to the attention of the necessary individuals. I do suggest that when you present information or make constructive suggestions that you don’t refer to the recipient as stupid. You may get a bit further that way. Definitely, a rose IS a rose, but talking nicely even to plants can help them grow.

Next post, I’ll spout a bit about what I think the key is to the success of the green market shift in light of the new administration and the American Recovery and Reinvestment Act.


  1. homedesign | | #1

    Rob, I am right there with you on the airtight concept...most do not take airtightness seriuously enough. Airtight before R-value.
    I think that every home should be constructed and commissioned capable of achieving ASHRAE 62. The homes should also be capable of exceeding 62 if the homeowner so chooses. If I understand Lstiburek ..the standards have overventilation built in already. Just look at Joe's top ten list.
    It does sound wasteful to me to encourage overventilation by awarding points.

  2. homedesign | | #2

    Reduction in Asthma symptoms
    Rob, how can you equate the reduced Asthma symptoms to EXTRA ventilation? Did you try the same house with code minimum ventilation first? Was there anything else about the new "green" house that may have improved the asthma symptoms? Maybe the prior problem was New Jersey.

  3. al rossetto | | #3

    Living in a 5-Star home with balanced energy ventilation reduces or eliminates colds and asthma. I have built a dozen and everyone agrees that you do not get sick living in these houses. Indoor air quality MUST equal or exceed out door air or you are going to get sick.

  4. GBA Editor
    Martin Holladay | | #4

    Builders Making Healthy-House Claims
    Thanks for sharing your experience, Alan. But I think it's important for builders to stay away from healthy house claims. Even Sam Rashkin, who designed the EPA's Indoor AirPlus program, agrees with me on this point.

    “It’s important for builders not to make healthy-house claims, or to make claims of better air quality,” said Rashkin. “We can’t say there is a cause/effect relationship between these measures and indoor air quality. Of all the factors that can hurt indoor air quality, occupant behavior so dominates air quality conditions — there are so many things than an occupant can do to exacerbate poor air quality — that you would have to be insane to make claims that these homes have better air quality. All we are saying is that we are reducing the risk.”

  5. Rob Moody | | #5

    Testing Air Quality
    Thanks for the comment Martin, and I fully agree with your comment, both about claims and occupancy behavior. As with energy usage, green building claims must be substantiated. I do not have a proven connection between the improved health of our homes' occupants and the indoor air quality of our homes. In good science, a hypothesis doesn't get accepted when there is supporting evidence and statistics. Instead the evidence "fails to reject" the hypothesis, a subtle but important difference. I can't say that our homes will improve the health of it's occupants. What I can say, is that in the one instance that the family's son had asthma problems, the symptoms disappeared when they moved into the home that we built. Could be that New Jersey air quality so much worse than Western North Carolina that it was the ambient air quality that caused the boy's respiratory problems. All of the research that I see on WNC air quality unfortunately does not support that that theory. Air quality in the WNC mountains is relatively poor due to the busy major traffic routes, and transported pollutants from the Ohio and Tennessee Valleys. On hot, humid, summer days we can have some of the worst low elevation ozone levels in the nation.

    There are way too many variables involved in this case to make a conclusion about the reason, but what I can fairly safely assume is that moving into our home did not worsen the kid's problems. In the other anecdote that I gave in this blog, the homeowner tested several IAQ factors with favorable results.

    It's a great cautionary measure for builders to avoid making claims about health. It would really open up companies to potential litigation of health related issues and IAQ. That's somewhere I don't think home builders and renovators want to go. The only way to make green building, energy efficiency and IAQ claims is to look at home performance. If interested in health of inhabitants, I would urge builders to get involved with third party standards and verification of building practices along with tracking the performance of their homes. It's true that anecdotal evidence does not correspond to health claims, but if you can show a trend, then that could be great marketing. The other critical component that absolutely can't be ignored is to substantiate your claims and EDUCATE your homeowners about the effects of their behavior on IAQ. We always had a green walkthrough with our homeowners at punchlist and again at the one year warranty walkthrough. EDUCATION IS KEY! I had to plead with one of our homeowners to keep humidity levels at bay by running the air conditioner in the summer. Keep a constructive line of communication open with former clients and it will pay off many times over.

    Thanks again for the comments.

  6. NilsDavis | | #6

    German PassivHaus research validates better IAQ claims
    Responding to Martin and Rob above, the German PassivHaus Institute has done quite a bit of post-build performance measurement to validate the IAQ claims for using heat recovery ventilators. So we don't just have to trust Rob or Alan's claims for better air.

    (PassivHaus calls for extreme airtightness, btw - 0.6 ACH at 50 Pascals - that's about 0.01 ACH at natural pressure.)

  7. GBA Editor
    Martin Holladay | | #7

    More details, please
    Okay, I'll bite. Citations, please!

    1. Who did the research?

    2. Are these papers (or executive summaries) available online? Are the articles in German or English?

    3. Most importantly, did the research verify merely that the air in Passivhaus buildings is cleaner than the air in non-Passivhaus buildings? Or did the research show health benefits to occupants?


  8. brad miller | | #8

    This is really frustrating to have these dirt and molds eating your homes slowly. You badly need mold removal procedures to totally get rid of it. Aside from being clean, health considerations are also an issue since this could affect any of the family members.

  9. Mike | | #9

    Great Tips
    Those are all great tips. I know when I have put in a chimney liner in some homes, they was no regard for the environment.

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