Return to the Basements Forum | Post a Follow-Up

 o
Conditioned Crawlspace

Posted by jjack (My Page) on
Sat, Aug 27, 11 at 0:41

I'm about to condition my ~600 sq. ft crawlspace by removing existing batt insulation, spray foaming the rim joists, installing Thermax foam board on the foundation walls, and putting down 8 mil poly (half the floor is dirt, half concrete slab). I have gotten two quotes. One was $9,000 and one was $5,000. The $9k seems insanely high, and even the $5k seems just high.

When I had the house inspected before I bought it, my home inspector guessed it would cost about $2k to do this. (He recommended that I take the above steps.) So, I'm trying to figure out which one of us is smoking crack.. Does anyone even have a ballpark guess for this?

Thanks


Follow-Up Postings:

 o
RE: Conditioned Crawlspace

Dow Thermax is quite expensive. I've read prices up to $80 per 4x8 ft. sheet. You can use cheaper XPS (extruded polystyrene), but it will usually require an "ignition barrier". But some municipalities may allow it installed with no barrier.

Labour costs are tremendously variable. Here, even general labour would be billed at $30+ per hour.

BTW, your crawlspace can't simply be enclosed without attention to other basics, such as radon mitigation and air supply/exhaust. (See Building Science Corp. link below for details.)

If you're not satisfied with the quote, you should seek competitive estimates from licenced contractors who specialize in sealing crawlspaces.

Here is a link that might be useful: Building Science Corp on Conditioned Crawls


 o
RE: Conditioned Crawlspace

Why are you going to put thermax board on the crawlspace walls?

It is expensive and in this application, it could be just as easily insulated with PSK fiberglass insulation.

Don't get me wrong, fiberglass is usually an awful insulation medium, however, in this case it does just fine.

Make sure that your liner is sealed to the crawlspace walls.

Get additional quotes. The 5K number is much closer to reasonable but still more than we would charge based on your square footages and work description.


 o
RE: Conditioned Crawlspace

it could be just as easily insulated with PSK fiberglass insulation.

Easy, yes. Cheaper, yes. But here's why you shouldn't install it.

From the assorted Ph.ds, building engineers, architects and building scientists at Building Science Corp.:

"Air permeable insulation such as fiberglass batts, fiberglass blankets or spray applied cellulose should be avoid when insulating crawl space perimeters and rim joist assemblies. The air permeance characteristics of these types of insulations do not prevent moisture laden air from accessing surfaces that may be cold enough to condense water." p. RR--0401, p. 3

And, since you don't mention your climate, if you're not in a humid hot climate, a vented crawlspace may be more efficient. (See link.)

Here is a link that might be useful: Building an Unvented Crawlspace


 o
RE: Conditioned Crawlspace

Climate: Minnesota. So, brutally cold 8 months of the year, hot and humid 4 months of the year.

About the Thermax, I currently have fiberglass batts in there (between the joists and on wall connecting to garage). The foundation walls are bare. The batts are not working much at all.. it is freezing in there in the winter and damp in the summer. I am going to turn this into a conditioned space.


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Basements Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here