Crawl space insulation
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Mark Bischak, Architect
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crawl space insulation
Comments (1)Instead of trying to fill in all that space, consider insulating from the outside with 2 ins. of XPS or 4 ins. of EPS foam boards with a protective covering above-grade. First, assuming you can at least get some access, cover the soil in the crawlspace with a min. 6 mil poly. Don't get stuck! Here is a link that might be useful: Insulation...See Morecrawl space insulation suggestions
Comments (7)So it's a vented crawlspace. A traditional bad idea. (See Building Science Corp. above.) But then you're using the crawlspace as the supply for the HVAC--in other words, forever sucking in humid air, but at the same time trying to dehumidify it. Sisyphus had it easier! Your crawlspace should be conditioned. In other words, it should be treated as part of the living space. You already are using it as a source of supply air for your HVAC. That means no vents, non-fibrous insulation at the perimeter (none on the crawl ceiling), a high-quality ground cover (not just sheets of poly) and provision for dehumidification, at least for the first few months after occupancy. Here is a link that might be useful: Green Building Advisor on Unvented Crawl Spaces...See MoreUnvented crawl space insulation
Comments (5)There are several problems I read here. Although it wouldn't hurt to insulate the ceiling under the room, I don't think that is your problem. You mention you did not see a return. It may have one but doesn't sound like it to me since you mention you keep the door to the room closed and the temp. drops drastically. If you are not taking air out of the room, you won't be letting conditioned air in. The size of the room also causes me to suspect there should be 2 supplies and 2 returns (without knowing the size of your existing system). You mention this room is an addition. I suspect the supply, return, heating, cooling systems were designed for the original sq. footage and was not upgraded with the addition. That doesn't mean things can't be done to improve what you have now. For us to really give you much in the way of more precise helpful information, we're really going to need much more information in return. We can steer you in a direction but you will need to have a qualified tech. to come in and do load calculations and make a true assessment of what really needs to be done. Just sitting here reading what you have mentioned, I can only guess (from experience) that you need some rework done. I may be wrong...maybe the original design was to allow for this addition. A Tech doing a site survey can surely better determine that....See Moreinsulating my crawl space: spray foam or fiberglass batts?
Comments (7)Try www.buildingscience.com/ for information about vapor barriers. Another good source for local building advice might be your state land grant university. I do not know anything about your floor finish. I guess you will cringe when I mention pre-finished flooring, but keep reading ;-) The spaces between the boards lets moisture through. With finished in place floors (poly finishes) you have a good vapor barrier. I guess that you understand the "sandwich" prohibition now. If you have a vented crawl space, off gassing will primarily be through the crawl. Ignition is a good question. I am afraid that I do not know much about fire and foam. I know that it burns and that crawl spaces raise fire insurance so it is a good thing to look into. Any kind of covering over the underside of your floor is going to increase the risk undiscovered or delayed discovery of rodent and insect damage. That includes batts, foam or boxing-in with rigid insulation. I do not know if there is any hard information about the relative risks of each method. The rigid insulation alternative is not one that has been addressed in this thread yet. It would be less expensive than foam, if DIY, but it is a lot of work. It has to be taped very well. You could take a hybrid approach and cover selected areas with foam board -- under the most troublesome plumbing areas for example. When you get done with that, you foam the rest. Low density foam pulls out pretty easily. I do not know about high density. You would just have to spray some more in after you make repairs. The problem would be finding the stuff that you need to fix. I would considerer tagging stuff before foaming if it will be covered by foam. You could use durable plastic tags in some color code. If you have a leak, water will run right through low-density foam. I do not think that is so with high-density foam. One important feature of spray foam is the air-sealing capacity. Batts will not do that. That is the problem with it where I live in the humid Gulf South. Air gets around batts even when freshly-installed. It is even worse when it sags. Humid air hits the cool floor, water condenses and does not dry well. Floor rot happens. Even with the best batt installation, the joists become the coolest thing under the house. Condensation happens there and then rot happens. These things worked great before AC existed, but not anymore....See MoreCharles Ross Homes
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last monthMark Bischak, Architect
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