Insulation question

Sorry if this is posted in the wrong forum.

I am planning on how to spend my summer. Since most of the insulation in my crawl space was installed upside down and is damp because of water problems, I am planning to re-insulate. I was wondering if I could install closed cell foam board instead of fiberglass. If so, how would be the best way to keep it in place between the floor joists. Would something like Liquid nails do the job? If so and I need to add an additional sheet or two, again, would it be O.K. to glue them together?

Do you recommend one brand over another?

P.S. I am working on the mositure problems and plan to replace the Poly that is on the ground with new, and make sure it is overlapped and sealed.

Thanks in advance for any input.

One more thing. I am going to remove all the vents and seal them up with hydraulic cement, as a couple of them are actually below ground level…

Just a few thoughts…If you use some type of styrofoam insulation you need to have a fire-rated product covering it because it gives off toxic fumes when it burns. And Iv’e see a lot of glue products that will melt the styrofoam and not bond very well.

Personally, I would stick to good old fiberglass batts myself. Why chance very toxic fumes in case of fire. It’s supposed to be very deadly?

Whenever I build over a crawlspace I use both fiberglass and foam. Install the fiberglass directly under the sub floor, then rip the two foot foam down in a table saw to fit snuggly between the floor joists, if doing this from the living space side, caulk or use spray foam as an addition air sealant. Once the fiberglass and foam are in place rip down strips of 1X pressure treated wood and nail to the bottom of the floor joist to keep everything in place.

Living in NH we have some brutal winters and this method has worked great for me. Remember to add ventilation and a moisture barrier if the ground is exposed.

Hope this helps.

I have great information (regarding crawlspace insulation) on my website at…

Your web site is awsome David, what don’t you have on your site???:smiley:

If my house is so involved in a fire that the floor is burning, I’d be worried about more than obnoxious fumes. :shock:

David, thank you for your link. I am going to print it out and read it tonight while I’m recovering from another day down in my crawl space.

I have had to call a plumber today because of a leaking cold water pipe.

While I was down there, I noticed since I opened my vents recently, to pipes are dripping like a rain forest. I had been using a Air Mover to try and dry out the dirt but I think it only brouht in more humid air. It has been very humid here in Norther Kentucky the last week.

I’m now turning the air mover around so it blows out the crawl space opening and hopefully, since it sucks air from both sides, it will draw the mositure and smell out side.

Any ideas how I can hook the air mover up to some kind of vent that I can use one vent opening to exhaust the mositure and smell. This machine was not cheap and I don’t really want to spend any more money on a de-humidifer, if I can use the Air Mover.

Thanks again to everybody who replied…

I’m not familiar with the name “Air Mover”. Humidistat controlled fans work very well in my experience. Suck air out of the crawl, like a window fan, and activate when air humidity is high. Do an internet search for that…you can’t buy them at Lowes.



I believe I have everything covered on my website. The reason why my sites get so big is due to my HI clients asking me questions after the inspection or before they purchased their home.

I decided to place the answer to their questions on my site so my future clients can be given a link to go to and it would save me time in explaining a situation over and over again.


Don’t waste your time with any sort of air mover. Upgrade your crawl space to a conditioned crawl space with a vapor retarder or an unconditioned crawl space with insulated pipes and vapor retarder.

Simply take my advice HERE.

Depends where he is. Uncovered styrofoam in a crawlspace is OK up here.

Good luck…