I have read most of the old threads on this, but I still have some questions.
We have an unvented crawlspace, but it is uninsulated. I want to move towards having a conditioned crawl, so we need to insulate around the perimeter. The crawl walls are block, and you can see the top of the foundation footings, so I was thinking about putting up foam board up to the floor joists, and then having the rim area sprayed with foam. If I use foam board, should I special order something like Thermax which it says can be left exposed in crawlspace, or is the blue or pink board good enough?
We also have a termite shield at the sill. If we have the rim area sprayed, do you not spray the shield for inspection purposes?
Finally, we currently have 6 mil black plastic on the floor over the dirt. Does it make sense to place foam board on top of the plastic to insulate the crawl from the ground?
Thanks in advance,
Aaron
Replies
pictures are worth a thousand words
hmmmm, your post perplexs me
Why do you want to condition the crawl space? Are you having moisture problems? Are there exposed pipes in the crawlspace?
If there are no ignition sources, then regular XPS foam board would be fine. If you're in a high-insect area, though, be sure to cap the foam board with a metal insect barrier. No problem spraying foam into the band area as long as insects cannot migrate into it.
It's probably unnecessary to insulate the floor. How deep is the crawlspace floor below grade? If it's 2' or 3' deep, there will be a good effective R-value from the earth.
Solar & Super-Insulated Healthy Homes
I should have mentioned that, but I suspect that you guessed that all of the pipes and ductwork are in the crawlspace. We have lived in this house two years, and this year especially, we are noticing that the floors are cold underfoot. I suppose that is natural to some extent, but hopefully having a warmer crawlspace will improve that somewhat. Foundations in Indy need to be 42 inches below grade--since the top of the footer is visible, I assume the floor is over two feet below grade--deeper in some places.
remember that foam must be covered by sheetrock
You should check with your local building inspector about whether rigid foam board in the crawlspace needs to be fire-protected.
Solar & Super-Insulated Healthy Homes
if we want to condition the crawl, we make sure there are no water issues
then we line the walls with borate treated eps ( PerformGuard ), either 2" or 3", we buy it with 1/2" gypsum bonded to the eps ( Branch River Foam... but google on "R-Control " in your area
then we blow the cavity with dens pak cellulose which is also treated with borates )
here's a pic of a new addition we did that way... but we also do it in existing crawl spaces
View Image
Edited 2/28/2008 10:26 pm ET by MikeSmith
That is interesting. I assume the drywall is for code/nonflamability issues. Can you finish that on basement walls?
I am working on resolving some water issues by improving the grading outside. Even though our house sits on top of a hill, we have a flat roofed house with no gutters. Most of the water falls off from four foot overhangs, but some of drops down right at the foundation. Someone also made the mistake in the past of running the asphalt for our parking area right up to the house, and the slope tends to come towards the house. I have started digging for french drains around the house, and that should take care of water coming in.
Bugs can't tunnel in XPS, right? If I go that route, I was thinking about sealing the top of the XPS near the sill plate but leaving the bottom open, so that if any water did get in, it would have a way out. What happens if you spray closed cell foam on a wall that has water infiltratrion?
bugs can get into any foam that isn't treated
the only treatment that i'm familiar with is Borates..
and the only foams i know of that are treated with borates are the ones i discussedMike Smith Rhode Island : Design / Build / Repair / Restore
>> but some of (the roof runoff) drops down right at the foundation. Someone also made the mistake in the past of running the asphalt for our parking area right up to the house, and the slope tends to come towards the house. << Personally, I think you have to fix thoes problems if you want it dry under your house.
In my town, BI's interpret the code to say that foam in crawlspace and rimjoists must be covered by a thermal barrier. For example, we had one project with a ICF foundation in a crawlspace, and the inspector had us cover the ICF with OSB. Thermax (and of course drywall) also qualify as a thermal barrier. This applies even to rimjoists that are between finished floors. I think there is some differences in how the code is interpreted (for example, see http://www.iccsafe.org/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=4;t=009428#000001), so best call your local building department.
Same here. Just had to cover rigid foam in basement ceiling. Plywood, osb or sheetrock. I used 3/8 ply.