Return to the Basements Forum | Post a Follow-Up

 o
How to insulate without rim joists?

Posted by tigerninety (My Page) on
Sat, Oct 27, 12 at 21:11

Hello,

So, we have a 1935 Cape Cod and (as some of you have seen) we're moving ahead on finishing our basement (much thanks to worthy for insulation guidance and pointers).

One of the regularly recommended steps is to insulate the rim joists. However, it seems that we don't have any.

Hopefully, you can see from the picture I'm including that, on one end of the house, there's a gap behind the joist closest to the cinder block wall. That cinder block continues up an inch or two behind the joist and is immediately topped by a brick-like material (sure looks like bricks but there seem to be some places where it's something that's brick-like, but hollow on the inside, like cinderblock but brick). There is nothing like a horizontal beam -- sill plate -- across the top of the foundation wall and there is no rim joist on top of that (as I've seen in pictures of modern houses on the web). By the way, this situation replicates itself at the 180-degree opposite end of the house.

Also, I hope you can see that at the end of that joist, where it goes into the wall, there is no rim joist there, either. This, of course, is the case for every parallel joist, from one end of the house to the other.

So, I'd been thinking that I'd use an expanding foam to seal the gap between the outermost joist and the parallel wall (though in some places that gap is two inches wide). Should I do that? What else could/should I do?

Similarly, what to do between the joists where they enter the wall at the far end?

Thanks!

Tiger


Follow-Up Postings:

 o
RE: How to insulate without rim joists?

Yep, same solution as where there are rim joists: spray foam or foam board and caulking.


 o
RE: How to insulate without rim joists?

Thanks for the above. What kind of spray foam should I use? Is there a particular kind that is consistent with the plan to use XPS against the cinderblocks below the joists? And, I presume I should be trying to spray as much foam up between the wall and the joist as possible, to fill the entire area up to the floor boards above, true?


 o
RE: How to insulate without rim joists?

Either closed cell polyurethane spray foam (ccspf) or open cell polyurethane spray foam (ocspf) is approved. However, open cell may require a further vapour barrier in cold climates.

There are lots of diy kits. But you have to follow all the safety precautions to the letter and there is clearly a learning curve. Or you can get a contractor.

You can get the same energy savings by cutting XPS boards to size and sealing with caulk and/or handheld single component sprays such as Great Stuff.

Installing Two-Component Polyurethane Spray Foam
Photo: Applegate Foam

Here is a link that might be useful: Building Science Corp.: Spray Foam at Rim Joist


 o
RE: How to insulate without rim joists?

Either closed cell polyurethane spray foam (ccspf) or open cell polyurethane spray foam (ocspf) is approved. However, open cell may require a further vapour barrier in cold climates.

There are lots of diy kits. But you have to follow all the safety precautions to the letter and there is clearly a learning curve. Or you can get a contractor.

You can get the same energy savings by cutting XPS boards to size and sealing with caulk and/or handheld single component sprays such as Great Stuff.

Installing Two-Component Polyurethane Spray Foam
Photo: Applegate Foam

Here is a link that might be useful: Building Science Corp.: Spray Foam at Rim Joist


 o
RE: How to insulate without rim joists?

Hello,

Many thanks, as always, for the speedy replies.

I'm afraid, though, that I probably wasn't as precise as I should have been. My fault.

I fully expect to use XPS between the joists perpendicular to the wall, cut to fit, and sealed with caulk or Great Stuff. No need to use the spray foam as they are doing in the pictures.

What I was wondering about is what I should use to fill the space between the joist that runs _parallel_ to the cinderblock wall and the cinderblock wall itself. In my original picture, it's that dark gap that starts in the center at the top of the photo and then "runs" away from you toward the bottom of the photo. That gap is the entire height and length of the joist (but the gap is not even and there are various random mortar protrusions, some of which you can see in the picture).

Should I use Great Stuff to fill that void, before I start adhering my XPS sheets below that? If not, what should I put up in that void (because I don't have a rim joist)?

Thank you very much!

Tiger


 o
RE: How to insulate without rim joists?

Too small a job for an outside contractor.

As you've probably found, the single component handhelds don't work well on overhead jobs. Wear goggles at all times!

But there are some professional guns for handheld foams that will work, such as those from Fomo, that retail for about $50.

Or you could push in sheets of XPS and make sure they're jammed tight against the exterior concrete using scraps of 2x2s or 2x4s. Not a perfect air seal, but it should preclude condensation problems.

(Sorry for the double posts and misunderstanding the question. Wouldn't be the first time!)


 o
RE: How to insulate without rim joists?

I've used Great Stuff in the same kind of space, tape some straws together to get a longer reach. If you use a good brand of tape it should work for 3 to 6 cans and you can get right into all those hard to reach spaces.


 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