Author Topic: Crawlspace Insulation!  (Read 3027 times)


  • Bristles
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  • Posts: 271
Crawlspace Insulation!
« on: April 23, 2012, 06:56:16 PM »
I've got a project that I'm not too excited to do, but I know it has to get done - so here goes.

I've got a dirt floor crawl space that is not well airsealed to the house itself. The crawl space has batt insulation in almost all of it (why would someone leave 80sqft uninsulated!) but they never strung it up propertly so it is now starting to fall down. As an FYI, my crawl space has between 18" and 24" or space between the joists and the ground with several places in which major beams are running a little lower and plenty of places where pex piping is just running everywhere.

So, my questions are:
#1. Order of operations, should I pull all of the insulation out - air seal - reinstall the insulation or is there a better way to handle this?
#2. Recommendations for air sealing - I've mostly used cans of foam for smaller jobs before, this requires something that can shoot upsidedown as well as handle a lot of volume. Is there an alternative to the "professional gun" or is that basically the answer? 
#3. Netting or the metal supports? I don't really want to do the string given how time consuming this is and my desire not to walk around on my elbows for more than a weekend.

Anything else I'm missing that I should be thinking about?


  • Handlebar Stache
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  • Posts: 1422
  • Location: Metro Boston
Re: Crawlspace Insulation!
« Reply #1 on: April 24, 2012, 08:19:46 AM »
First, think carefully about how what you're doing will affect temperature and moisture.


  • Bristles
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  • Posts: 271
Re: Crawlspace Insulation!
« Reply #2 on: April 24, 2012, 06:27:18 PM »
Thanks Velocistar237- I'm not sure what to say about the affect on temp and moisture other than to say that I didn't see/smell any fungal growth when I went down there the other day and I live in a climate (the Pacific NW) where there is moisture everywhere.  It was breezy.

If I were to guess, I would say that moisture from the crawl is heading into the house and heat from the house is heating the crawl. I don't think insulating the walls is in my budget. . .I might consider trying to install a vapor barrier on the floor, but because the house is post and beam it would be a giant pain in the butt and for that matter - wouldn't the sono-tubes and ancient concrete blocks wick moisture up anyway?

I guess, I'm dealing with a 1940's house and need to figure out the best rehab I can do. If I was building new I would eihter do a slab on grade or full basement. . .but I'm dealing with the cards I'm dealt with. Do you have any direct advice on best practice?


  • 5 O'Clock Shadow
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  • Posts: 84
  • Age: 49
  • Location: Raleigh NC
Re: Crawlspace Insulation!
« Reply #3 on: April 25, 2012, 07:26:04 AM »
I'm having the same issues on my house and if I stay there long enough, I plan to seal the crawlspace.  In such case, I'd remove the old insulation, get some heavy plastic and come down the brick walls with it.  Then cover the floor, sealing all plastic seams together.  Add a dehumidifier, drain it outside, and call it a day.

With no ability to take in air, it isn't necessary to seal the floor beyond sealing against critters.