Basement Rim Joist Insulation


  #1  
Old 01-11-13, 06:53 AM
C
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Basement Rim Joist Insulation

Hi all, here's my newb question of the day (I'll probably have one a day for the next few months )

My basement is concrete block foundation and in the unfinished areas (shop/furnace area and washer/dryer area) there is a good foot or more of space above the blocks for the wooden rim joist.

The previous owner stuffed backed batting insulation into these areas around the joist, but it's looking pretty rough now. The Batts have sagged or crumpled and exposed the joist in many places and some of the backs are discolored and worn (condensation probably). The inspector who looked over the house when we bought it basically said "nah it's fine, leave it be" but I can't imagine that old stuff is doing anywhere near its optimum job.

Would I be better off just pulling it all down and replacing it with new batts? Or is there a more preferable way to insulate rim joist areas (spray for example?)


And if I do pull it all out, is there anything I should do to the sill and rim joist while they are exposed and I've got the opportunity?

Thanks all!
 
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Old 01-11-13, 07:13 AM
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Spray foam would be best. If the current insulation is not covering the entire space, I'd replace it.
 
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Old 01-11-13, 09:40 AM
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I agree, starting over is best. This is an important area, the inspector is exposing his lack of knowledge, that needs to be well air sealed and reasonably insulated. There are different approaches, but fiberglass insulation isn't one of them, unless added over the final job, but even there, it works poorly.

There is another concern with a block foundation. If the blocks were left hollow, then cold air is circulating from top to bottom. The top that is exposed to the outside is providing a direct path to the entire inside block wall. One approach would be a couple of inches of rigid foam, top to bottom, in addition to the air sealing and insulation for the rim joist area.

Bud
 
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Old 01-11-13, 04:55 PM
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Why are you looking into this? Do you want to keep the basement warmer, or is it the floor above that you're concerned about?
 
 

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