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Tricky Crawl Space Insulation Question

josephny | Posted in General Questions on

I have 4 cottages that were at one time seasonal (not insulated).

The cottages are built on concrete piers with open crawl spaces that vary in height from 2″ to 2″.

Over the years I’ve had them all insulated with spray foam.

But, the floors in all the cottages are very cold during the winter, probably because the spray foam could not be applied uniformly and completely from underneath due to the limited space.

I understand that moisture coming up from the ground is natural and that because of that moisture, enclosing the crawl space around the perimeter of the house can result in a buildup of moisture and all the resulting nastiness.

What can I do to prevent the cold from getting under the house?

A related and equally challenging problem is that the water feed and waste lines are under the house.  I’ve wrapped heat tape around them but every Winter something freezes.

Very much appreciate any suggestions.

Thank you!

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  1. Expert Member
    BILL WICHERS | | #1

    You would need a skirt if the piers are truely open (no walls at all), then you'd insulate the skirt and cover the "floor" with polyethylene, the same way you'd encapsulate a regular crawl space. Another option might be to run rigid foam under the floor joists and doing a careful job of sealing the rigid foam as an air barrier. I would use foil faced polyiso for this. Which option you choose depends on lot on the specifics of your particular site.


  2. josephny | | #2

    I was planning on a skirt all around (wife wouldn't let me leave the insulation board exposed -- I know this from experience).

    Last Winter I screwed some green board to the underside of the floor joists. I think it might have helped a little, but I couldn't do a complete/thorough job because access was impossible, so there were large areas without the boards.

    Thank you!

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