Rim joist insulation

[Dune]

I am going to insulate my rim joist in preparation for installing staple up pex. What thickness foam should I use? Is 2'' good or should it be thicker?

 

[billb3]

I used 2 inch with the foil.
Where I could stick my fingers outside (where the mice were coming in) between the sill plate and rim joist I even put foil tape on the exposed ends of cut foam.
Everywhere else I didn't bother.

I cut the pices about 3/8 inch shy and used expanding foam llike glue on all 4 edges to hold in place.

Anywhere there was a wire or pipe penetration I just cut in half at the penetration, cut a circle and foam filled the gaps.

 

[pybyr]

I agree that expanding foam can be useful for this, especially if you have varying sizes/ spaces to fill in addition to easily-cut foamboard shapes. I got one of these last December--

(broken link removed)

-- if you're going to be doing this (expanding foam) in any quantity, it's far easier, more controllable, and less expensive than the hardware -store throwaway can-with-straw foam dispensers. You can also use part of a foam cartridge, close the gun (via a knob on the back) and set it aside for hours or maybe even days - and then come back and use the rest of the foam (unlike the throw-aways that clog themselves shut if set aside for more than a brief while). Just _don't_ get it on you- it's quite an adhesive (I've actually used it for that, also, in a pinch, and for non-critical uses).

You can get these other places, but the above place has a location near me, and their prices seem better than some other options I'd found (and they're good folkls)

 

[dave11]

I used the 2 inch thick Foamular, R-10. Any thicker and it gets hard to cut and place, though I'd recommend cutting it on a table saw if you have one, to get really neat cuts. I had read that the foamular is better than using any foil-faced insulation, which could in theory trap moisture against the rim joist, though I'm not sure how much that really happens. Since you're installing radiant, you probably will need to leave an air space between the foamular and the radiant reflector, to keep the joist bays warmer.

 

[Dune]

I used the 2 inch thick Foamular, R-10. Any thicker and it gets hard to cut and place, though I'd recommend cutting it on a table saw if you have one, to get really neat cuts. I had read that the foamular is better than using any foil-faced insulation, which could in theory trap moisture against the rim joist, though I'm not sure how much that really happens. Since you're installing radiant, you probably will need to leave an air space between the foamular and the radiant reflector, to keep the joist bays warmer.

So if the two inch is only R-10, wouldn't 2 layers of 2'' be more apropriate?

 

[velvetfoot]

Here's a thread with my tortuous journey.
I went crazy. It gets harder and more expensive with more layers.
https://www.hearth.com/talk/threads/31340/

 

[Dune]

Here's a thread with my tortuous journey.
I went crazy. It gets harder and more expensive with more layers.
https://www.hearth.com/talk/threads/31340/

Thanks Velvetfoot!
I was thinking 2 layers for R-20 would be reasonable, but after reading that thread I think I will get a Pro with spray foam. I figured a couple days, not a couple months. Excellent, neat job you did by the way.

 

[LLigetfa]

Check fire codes for flame resistance requirements. We used spray foam on gas pipeline trenches for erosion protection and the stuff went up in flames like a giant marshmallow. Spray stucco over the foam for fire retarding.

 

[Dune]

I agree that expanding foam can be useful for this, especially if you have varying sizes/ spaces to fill in addition to easily-cut foamboard shapes. I got one of these last December--

(broken link removed)

-- if you're going to be doing this (expanding foam) in any quantity, it's far easier, more controllable, and less expensive than the hardware -store throwaway can-with-straw foam dispensers. You can also use part of a foam cartridge, close the gun (via a knob on the back) and set it aside for hours or maybe even days - and then come back and use the rest of the foam (unlike the throw-aways that clog themselves shut if set aside for more than a brief while). Just _don't_ get it on you- it's quite an adhesive (I've actually used it for that, also, in a pinch, and for non-critical uses).

You can get these other places, but the above place has a location near me, and their prices seem better than some other options I'd found (and they're good folkls)

Thanks Pybyr. Fortunately I have a customer who is an insulation specialist. He wants some ornamental work and is going to pay for it with a big insulation upgrade of my home. I didn't realize how big a job the rim joists would be, so now I will just have his crew do that as well.

 

[velvetfoot]

Dune, that sounds like the best solution!
I'm not the quickest worker, but it did take a while.
It's too bad that foam is flammable like that - it'd be nice if it wasn't.
I'm going to drywall my basement ceiling and walls...as soon as I figure out how best to stack that big pile of wood, lol.

 

[Wet1]

Would there be much to be gained by sticking some R-13 fiberglass up in there?

 

[coolidge]

Check out this website for fire retardent paint you can apply yourself. As usual follow the manufactures recommendatios. TPR2.com

 

[gpcollen1]

(broken link removed to http://www.buildingscience.com/documents/information-sheets/5-thermal-control/basement-insulation/?searchterm=rim) joist

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