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Old 01-16-2012, 10:24 AM   #16
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I don't want to take away from the original poster question. Just adding my experience.

Bob, I don't see where the link states no thermal or ignition barrier required. Dow can state whatever it wants. The building code says different unless Dow has provided testing data and the product has been approved.

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Old 01-16-2012, 10:51 AM   #17
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In any case you need to follow you local codes. Unfortunately they are very outdated and flat out wrong when it comes to energy efficiency retro-fits. Codes will be changing for 2012 when local officials adopt them. big changes.
1) vapor barriers are not to be used in mixed climates
2) exterior foam insulation is required to stop thermal bridging
3) air sealing and a blower door test are required
4) vapor retarders over dense packed cellulose are not required
5) Mechanical ventialation (HRV) will be required
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Old 01-16-2012, 10:59 AM   #18
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Yes, I agree with your statement about the code being outdated. But as we know, what's in the current and local code is what we have to comply with, like it or not. Or do it as we want to do in OUR house and hope it never becomes and issue.
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Old 01-16-2012, 11:15 AM   #19
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if it not to be inspected and building science shows it is the right way, I would go with the right way. Poly on warm side of walls for mixed climates is an excellent example.. By code grow mold. As a contractor I install the poly get inspections and rip it out. Inspector knows this is being done and agrees with it. If fact it was his recommendation. code here still wants cross vents in a crawlspace. yet when doing a fix we immediately seal these off. (note DOW says to do the same thing) Building Science is relatively new. And codes were not built to local conditions. Our housing stock is built horribly as a result.
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Old 01-16-2012, 11:59 AM   #20
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I have no problem with what you wrote but there are limits. Yes?

To the issue of covering foam board, my understanding is protecting the foam from fire and the potential gases it produces when burning.

Will those gases make it into my living space before I know there is a fire in the crawlspace? I have no idea. A smoke detector in the crawlspace (and attic) might be a good solution.
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Old 01-16-2012, 12:14 PM   #21
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yes a good solution. Crawlspace ceiling should be as air tight as you can get it. The smoke is bad, but you couch cushions, OSB, flooring, paint and much more are much worse.
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Old 01-16-2012, 01:48 PM   #22
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Crawlspaces and attics and published information to pass inspection: knee wall insulation help

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Old 01-16-2012, 05:55 PM   #23
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Quote:
Originally Posted by Bob Mariani View Post
yes a good solution. Crawlspace ceiling should be as air tight as you can get it. The smoke is bad, but you couch cushions, OSB, flooring, paint and much more are much worse.
Why would a crawlspace ceiling need to be air tight if it was being treated as sealed/conditioned?

I guess you could stomach cancer is worse than lung but that doesn't mean I want either.

Code is code....and the foam is supposed to be covered. Random dismissal of a tenant in the code is not exactly advisable.
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Old 01-16-2012, 07:22 PM   #24
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a crawlspace is normally not intentionally conditioned living space. As such it is considered outside the building envelope. The insulation (thermal boundary) and air sealing (pressure boundary) should be aligned. Also air in the crawlspace would rise due to stack effect and it is not the quality of air you wish for your family
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Old 01-16-2012, 07:51 PM   #25
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If you turn it into a sealed crawl, isn't the pressure and thermal boundary the crawlspace stem wall at that point?

If that is the case, why is the pressure boundary required at the ceiling? At that point you are mixing layers. Air and insulation, in the same plane, is the outside wall.

As part of any crawl space sealing protocol, the floor is going to be covered an with Poly and sealed at the stem wall so there should not be any issues with dirt smells/odors.
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Old 01-16-2012, 08:35 PM   #26
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If you're sealing and conditioning the crawl space, the air quality shouldn't be an issue.
Per the building science RR-0401:
"Crawl spaces should be designed and constructed as mini-basements, part of the house within the conditioned space."

Since the code allows/requires conditioning, including the exchange of air between the occupied space and the crawl space, it appears the issue is not that the crawl should not be considered outside the building envelope, but part of the functioning system of the home.
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Old 01-16-2012, 08:40 PM   #27
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Quote:
Originally Posted by CrawlSpaceMoist View Post
If you're sealing and conditioning the crawl space, the air quality shouldn't be an issue.
Per the building science RR-0401:
"Crawl spaces should be designed and constructed as mini-basements, part of the house within the conditioned space."

Since the code allows/requires conditioning, including the exchange of air between the occupied space and the crawl space, it appears the issue is not that the crawl should not be considered outside the building envelope, but part of the functioning system of the home.
This is my point exactly. Thanks.

It is either sealed (i.e. conditioned) or vented. Not a mixture of the two.
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Old 01-16-2012, 09:03 PM   #28
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Doesn't the Thermax Sheathing meet the requirement of r314?
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Old 01-16-2012, 09:05 PM   #29
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Some say yes and some say no. My only point in this discussion to make sure you get approval from your local inspector before you take chances of falling on the wrong side of the code.
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Old 01-17-2012, 07:28 AM   #30
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We should be commenting on old construction not new. See original posters question.

In a perfect world if I were designing a new house and needed a crawlspace I would desing and build a mini-basement or "basement for trolls" as I remember it being described.

I would not overlook the HVAC requirements (heat gain/heat loss) if I planned to condition my crawlspace. So I won't be installing a new HVAC system to accomodate a conditioned crawlspace. Please don't write that the crawlspace load would be of no concern and tapping into the existing HVAC would be ok.

As to Thermax, or any other glass-fiber-reinforced polyisocyanurate, that product was my orginal choice until I read that it absorbs water. Also, the foil would not allow any moisture that enters the brick/block wall to dry to the inside. Not sure why I want that, but that was needed.

I do not have a Phd in building science. I'm a home owner who wants to know what is being done to my house and why. It's my money, my house and I live in it.

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