Crawl space weatherizing

braytonakSeptember 9, 2007

I just finished reading a similar thread, but think that some of the points made don't apply to my situation.

An Energy Rater looked at my home and said the crawl space (exposed foundation walls, approximately four to five feet of height with unsealed sheets of plastic strewn on the sandy, 90% dry, ground) is where I could make the biggest improvement. He gave me a diagram that shows what I should do. This is all fine and dandy, but it made me wonder. Here's what the diagram says to do:

1) Lay vapor barrier across the exposed earth floor and seal with caulking at all edges and penetrations.

2) Apply vapor barrier to foundation walls and seal with caulking.

3) Install insulation over the foundation walls, as well as on ground inward from the wall for four feet.

4) Seal the perimeter of the floor joist area with styrofoam sheets and seal.

This is all based on a climate that can see -20°F days. The crawl space is partially conditioned, as in it gets its heat from whatever leaks from the heating pipes, hot water pipes and through the floor. Ventilation is allowed in the summer (May / June through September) through two naturally aspirating vents in the wall.

This sounds to me like a way to actually create problems with mold under the barrier or behind the floor joist perimeter.

My biggest questions are A) Should I really be sealing a crawlspace to the point that it could become a swimming pool, B) Should the walls have traditional faced or unfaced fiberglass insulation, 2" styrofoam panels (faced with foil) or some professionally applied spray-on foam, which probably eliminates the need for a vapor barrier on those walls?, and lastly C) How would those insulating products be attached? There is currently about two feet of insulation that is stapled to the horizontal framing on top of the cement foundation, which is then just hanging over the wall. (Doesn't reach the ground by any stretch of the imagination.)

Thanks to anyone who makes it through my lengthy questioning!

Thank you for reporting this comment. Undo

Look at the Building Science website, they will have a lot of info on the why's and how-to's to accomplish what the energy rater has proposed. Also, they will suggest that you keep the crawl vents closed/sealed and make the crawl into a conditioned area, like you would a basement.

If the crawl is assembled and sealed properly, it shouldn't become a swimming pool; drainage and a sump pump/pit can always be incorporated.

Yes, spray-on foam can accomplish the sealing and insulation function with one product, but it is a pricey way to go. You will have to be the one to determine if the cost is right for your situation.

Here is a link that might be useful: Bulding Science paper: Conditioned Crawlspaces

    Bookmark   September 10, 2007 at 10:53AM
Thank you for reporting this comment. Undo

Thank you for the information! I'll have to analyze that document closely. Perhaps the State has similar information that can point out any differences for this climate.

    Bookmark   September 11, 2007 at 2:31AM
Sign Up to comment
More Discussions
water in unfinished basement
Well its in the 50s here in NJ and the snow is melting....
basement flooring - tile or finished concrete
we're planning a reno that will include expanding and...
Str'l Wood Floor + CrwlSpace vs Concrete Slab
Hello, We were discussing our plans with a builder...
Ductwork revisions
I am working on re-finishing a basement that was originally...
Flooring System over a basement
In my current house we used 16-18" deep floor...
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™