Crawlspace Wall Insulation

Ask The Builder · 68: Crawlspace Wall Insulation

Available on iTunes

Animated GIF by Marty Hovey Copyright 1995 Marty Hovey

Crawlspace Wall Insulation Podcast:

Tim Carter received a great crawlspace wall insulation email from Craig who lives in Ohio. He sent amazing photos you can see below. Craig wrote:

"Hi Tim,

My crawlspace is about 660 square feet. I've attached pictures of the current condition in the crawl space. The insulation was simply nailed into the sill plate board resting on top of the foundation wall.  The result is an on-going struggle to keep insulation hanging in place. How best can I keep it in place?"

Look at Craig's photos then LISTEN to Tim's advice in the podcast at the top of this page.

You can also read below, look at other photos and WATCH the videos:

crawlspace wall insulation

The following photos are from my daughter's new home. THIS is how Craig should finish his crawlspace:

crawlspace wall insulation

What is the Best Crawlspace Wall Insulation?

The best crawlspace wall insulation is closed-cell foam. You keep it in place using a special adhesive that fits in a caulk gun.

Who Makes the Best Foam Insulation?

I feel Dow and Owens Corning make superb closed-cell foam insulation. I have the Dow blue board under the floor of my shed. Watch the video just below:


Related Links:

Tim Carter Shows How to Work with Foam Insulation Board

CLICK or TAP HERE to get FREE BIDS from local insulation contractors who can install closed-cell foam in your crawlspace.

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12 Responses to Crawlspace Wall Insulation

  1. Listened to the podcast. Agreed with your advice on the foundation wall but you made an error in stating the white foam used in cups is not closed cell (3 minutes in). EPS (Expanded polystyrene), the white foam typically used in foam cups and insulation board is closed cell. Styrofoam is a brand name using XPS/EPS. It is a vapor barrier unlike fiberglass insulation, which is another reason to use it on foundation walls. EPS is beads that are molded or cut into various sizes and shapes while XPS is extruded sheets.

    • Thanks, Mike. I just assumed the cups were open foam. A quick online research check would have yielded the correct information! I hate it when that happens. UGH!

  2. foamboard is the way to go for foundation insulation.for between joist roll insulation with nylon netting to hold in place.

  3. Well here in the Midwest all of the pest control companies (Think termites) ...orkin , terminex, Adams etc strongly urge contractors and DYI to leave a minimum of 4 inches of concrete wall exposed Top or bottom to be able to immediately spot mud tunnels used by termites. Yes, you will eventually get termites ....unless you’re lucky enough to win the biggest lottery which most of us aren’t.
    Do it right, not over. Leave an inspection site for yourself or your termite inspector to locate termite activity before they get to the sill plate and rim joist.

  4. Tim. It is against building code in Ohio to use foam board in crawl space unless it is covered with drywall. Or wood

  5. Good Video. Good way to help keep water lines in crawl space from freezing in Winter in Northern states or provinces.

  6. Fiberglass roll insulation can also be held up under a floor over a crawlspace using purchased (or I made from clothes hangers) stiff wire supports between the joists at about 2 foot intervals. Cut the wire about 3/4 in longer than the joist spacing. Seems to work ok for me. Before that, insulation batts did fall out occasionally.

  7. You could use InSoFast, Check it out if you have never heard of it.
    I've used it on my basement and it's great!

  8. We call 'em tiger teeth, or insulation supports down south here. Put one every 3 to 4' the whole length of the insulation batt and it will stay up between the joists.

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