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Insulating a basement

Posted by jimbo22s (My Page) on
Sat, Oct 25, 08 at 15:20

How do I insulate an area that I cannot cover with drywall if I plan to use 1" XPS? For example, the area behind the sump pump, or the area behind the water meter. I plan to box in each area and use a bifold door for access. I live in a "Cold" zone.


Follow-Up Postings:

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RE: Insulating a basement

See link for a partial list.

Here is a link that might be useful: 15 minute thermal barrier


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RE: Insulating a basement

Thank you.

What does "homebound" mean by this in the description of how he insulated the rim joist area?

"applied solid pieces of foam in each space, followed by spray insulation around the edges".

Is the solid foam XPS or EPS? Is the spray insulation like "Great Stuff"?


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RE: Insulating a basement

Here's what I meant. (We're talking, of course, about the spaces around the inside perimeter, such as above the foundation wall between the joists, etc.)

I took measurements of the rectangle space (eg. 12" x 9" or whatever it is, then I cut XPS (foamboard) with a bread knife, or utility knife, etc. Then put a dab of foam adhesive on it and stuck it up in there. Since the cut isn't perfect, I filled the gaps with canned foam, such as so-called "Great stuff". I'll warn you that using that foam is difficult and very messy, since there's little room to invert the can while you spray up there. Also, "Great stuff" nozzles snap off really easily, so you end up getting sticky foam on yourself and ruining your clothes. If you use canned foam, try to find the DOW foam instead (their nozzles snap off much less often), and get some vinyl tubing (I forget the size) and rig up an extention to the canned foam spray tube. (I taped the extra length of tubing to heavy, stiff wire, and bend it as I needed to work up there.)

Bottom line is that the way I did it was a mess. Might want to just invest in tiger foam, etc, and spray each space instead.

You asked about insulating behind the water meter, etc. Well, what I did behind my gas meter was glue some solid pieces to the wall (best I could), then slip some plastic behind the meter, and then sprayed foam behind the plastic in the gaps. Result is that the foam is snug behind the meter, yet if I have to remove it, it won't be stuck to the meter itself. Not sure if it's proper, but that was my way to do it.

Good luck.

Homebound.


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RE: Insulating a basement

slip some plastic behind the meter, and then sprayed foam behind the plastic in the gaps

This is not a 15-minute thermal barrier that is required. If you've ever smelled just a whiff of burned foam, you'd appreciate the importance of providing that barrier.


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RE: Insulating a basement

With my gas meter, I then boxed it in and installed a 1/2" plywood door for it. Not sure, but I think that satisfies the 15 min thermal barrier" between the foam and the habitable space requirement.

Anyhow, if there's room for putting a piece of 1/2 drywall over the foam behind the meter, that's better, I suppose.


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RE: Insulating a basement

Thank you for the explanation.

What percent efficiency would you estimate that I would lose if I simply glue a piece of XPS up in the rim joist as close to size as possible and skip the canned foam? Will the batt that the builder stuck up in there help at all if I replace it after I glue a piece of XPS?


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RE: Insulating a basement

If you put the batt insulation on top of the xps, sure it would help some, but it would be better to seal the foam. Anyway, before you put anything up there, make sure to caulk/seal all air gaps - very important. (On a cold, breezy autumn day it's easy to find them by sticking your hand up there.)


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RE: Insulating a basement

sticking your hand up there.)

Pros use a smoke pencil.

Less impressive looking but still effective, you can use an incense stick, feather on a stick or piece of light cellophane.

Here is a link that might be useful: Air Leakage Control


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RE: Insulating a basement

What size fastener would I use to mechanically attach 2" XPS? Is a zinc plated fender washer sufficient?


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RE: Insulating a basement

That's what I've used. If you can find an equivalent plastic fender washer, that would be better as it would reduce the conductivity of cold through the XPS.


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RE: Insulating a basement

The concrete screw anchor should be 1/4" diameter by a maximum of 3.75" long. If the wall is of unit masonry (block or brick) You can easily use a shorter screw. I use a slotted hexwasher head and do the final tightening by hand.


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RE: Insulating a basement

Do I first create a pilot hole or will the concrete screw penetrate the poured concrete without too much trouble?


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RE: Insulating a basement

Pilot hole first. Unless you hit a stone, the drilling is a snap with a hammer drill. (Tapcon, the most widely known brand of concrete screw, provides drill bits of the appropriate length in each box of screws.)


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RE: Insulating a basement

What specifications should I look for in a hammer drill to attach 2" XPS to poured concrete with a 1/4 x 3 3/4 Tapcon? I would like to make the job go as easy as possible but am not likely to use the drill after this project. I see Lowe's has a $59 drill and a $622 drill and every point in between.

Where can I find an alternative to Tapcon that might run a little cheaper? I did not see anything at the major stores.


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RE: Insulating a basement

Also, I do not see a drill bit in the box of Tapson screws that I bought. What size and what type of bit do I need to drill a pilot hole?


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RE: Insulating a basement

The bit should be one-inch longer than depth the screw is going into the concrete. In your example, you'd need a bit of at least 2 3/4" long. You might be able to get by with a shorter concrete screw. I wrote that the maximum embedment is 1 3/4"; the minimum is 1". If the wall is irregular, I'd use the longer screw to be sure.

Boxes of 100 Tapcons usually include a bit. You can also buy them separately. You'll sacrifice a few on most jobs.

I've used cheaper store brands of concrete screws successfully, in my case RONA. But the Tapcon bits are top quality.

Even a $100 hammer drills should do the job satisfactorily, as long as you take it easy and don't overheat it. A heavier duty drill can be used for a much longer period. All the hammer drills I've seen can also be used as regular drills.


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RE: Insulating a basement

Are these Simpson achors likely to work as well as Tapcon? I can get a couple of bits separately.

Here is a link that might be useful: Simpson Anchor


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RE: Insulating a basement

Are these Simpson a[n]chors likely to work as well as Tapcon?

As Sarah might say, "You betcha!"


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RE: Insulating a basement

Thank you for the replies.

Can you describe the process to mechanically attach the 2" XPS to the walls? I have cut all the pieces to size but it is hard to picture how it should work. I have plenty of glue if I should use it too.


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RE: Insulating a basement

I am in the same boat. The 2" XPS I bought is slotted and accepts fur strips. I know how to secure that. The 1/2 stuff will be secured with Tapcon type screws using a washer, perhaps 5 per 4 X 8 sheet. I noted that plastic fender washers are available, not sure where. I too am looking for a more specific how best to secure.....

Also, with 2" xps....in some areas I am drywalling directly onto the XPS (in closets and such. I will however need an outlet or two. The XPS brochure says shallow outlet boxes will work. Do these come in plastic and how the heck to you secure these...I know you can route a channel for the wire and box (is this up to code?) but how is the box secured?


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RE: Insulating a basement

jimbo22s: Too late now. But I would only cut the board as you need it.

Secure one board at a time. I found it easier to install the boards vertically.

First, if the adhesive holds, use it to keep the board in place. (I've only boarded poured walls and the adhesive was useless due to the irregularities in the wall.)

Once the board is in place by glue or just by holding it, drill one pilot hole at a top corner. Then, simply put the fender washer over the concrete screw and drive the screw in. Now that it's secured, you've got two hands to drill the rest of the holes and put in the screws--which always makes the job easier! I usually used about four screws per 2x8 board. To reduce endless stooping down, I use a carpenter's pouch to hold screws, washers and drivers etc.

Since you haven't used t&g (tongue and groove) boards, be sure to keep the boards as tight as possible to each other and tape the seams with Tuck Tape or equivalent.


Seal all seams with construction tape such as Tuck Tape

andrelaplume2

The boxes are secured to the foundation wall with concrete screws. Shallow boxes may or may not be Code compliant in your jurisdiction. (They weren't in mine, but now are.)


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RE: Insulating a basement

Thank you for the reply. This is a poured concrete wall about 10 years old.

Do I need to worry about concrete debris in the hole after I drill it?

What is a rough estimate of how many bits I would go through to drill 200 holes? 5 bits? 10? 50?


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RE: Insulating a basement

Do I need to worry about concrete debris in the hole after I drill it?

No.

how many bits

Buy four. That should be enough.


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RE: Insulating a basement

Thank you.

The boards do not fit tight in some places if they sit on the floor. I assume the floor is not level. Should I keep them flat on the floor and tape the larger seam or should I install them tight and have a gap at the floor?

Is either a hex screw or a phillips easier to work with or is it about the same?


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RE: Insulating a basement

I was referring to the seams between the boards. At the bottom, just keep the boards tight to the wall; the tape doesn't hold on concrete.

I prefer the hex head as it sits more directly on the fender washer. But I suppose Phillips head screws can work ok too.


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RE: Insulating a basement

I started insulating the rim joist in my basement using the same method as HOMEBOUND(1in xps cut and placed to size.) what a pain. Everything you said about great stuff is true. Though the tubing Idea is a very good trick. The problem I am having is the number of wires which run along the bottom plate on the 2x6. this prevents me from being able to placing XPS flat on the surface and sealing around the base of the sill. I Have thought about hollowing out a portion of the XPS to cover the wires,though this would certainly leave air gaps. I am considering even getting a DIY spray foam kit and spray the bottom plate and the XPS i have already put in place. any suggestions would be welcome. also, going to use 1.5in XPS on walls, screwed in as described above. No FG insulation. Walls set on 1/2XPS.


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RE: Insulating a basement

Unless the sill is on top of foam, I'd run a bead of caulking along the sill to stop air infiltration and not worry too much about the XPS being perfectly tight to the wall at those points.


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