# Insulating rim joists I can't see



## Windows on Wash (Aug 30, 2011)

Pictures?


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## MLMIB (Aug 12, 2010)

That is looking right at the soffit. There is a 1" piece of wood near the top of the wall, but past, from what I can tell, is the ducting.










here is looking down the soffit


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## Windows on Wash (Aug 30, 2011)

Sounds like it might be a recipe for disaster to be perfectly honest.

There are closed cavity foams that are used to retrofit insulate interstitial wall cavities that were either under insulated or uninsulated, however, I don't know of any DIY applications for said insulation methodology.

How tight is that ductwork to the ribbon board? I.e. how much clearance from that outside wall do you have?

If there's a decent amount of clearance, it would probably make better sense to rip out the strip of drywall from the bulkhead, insulate it via standard applications, and and just re-drywall that section.


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## MLMIB (Aug 12, 2010)

if I took down the ribbon I'd have about 2 inches, maybe, of space to work in. if I took down the drywall I'd just be staring at duct. The ducts might be 2 inches up, but certainly not enough for a standard install of putting foam boards up and sealing it with spray foam from a can.

I had some open cell foam installed in my walls a few years back and they did it by sticking a 2 inch hose in the wall through maybe a 4 inch hole and filled the entire cavity that way, I was hoping I could do something similar but with closed cell foam.

Any thoughts? or should I just look for a pro to come over and do it since they probably have better systems with more pressure to work with a longer hose.


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## Windows on Wash (Aug 30, 2011)

Might be easier to have a pro look at it. 

Make sure the perm ratings are right at the bands as well.


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## Gary in WA (Mar 11, 2009)

IMO, remove the ledger board, check to see if you actually need it after the work- supporting ?. Add some 1/2" thick polyiso board to the rim joist, foil-faced with caulking on the top edge/sides before installing- for air tight seal. Then just compress some fiberglass insulation pulled from batt, to fill the joist cavity (interstitial). Problem with foam, it may cause a crease in the ducting that could restrict air flow/turbulence or move/miss-align the run/joints. I've used the clear tubing 2' long with the canned foam before but even the door/window (low-expanding) may expand too much in those tight areas- and very difficult to keep air-pocket free- especially with no vision above the pipe. Compressing R-13 (3-1/2") to 1" will give you at least R-4.4 per inch thick...

Gary


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## Windows on Wash (Aug 30, 2011)

That's a good idea from Gary.

Post up a picture viewing the home from the outside.

If you have vinyl siding it's much more doable as compared to some other, less serviceable claddings.


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