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Sealing/insulating rim joists - slight confusion


xvimbi's Avatar
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Join Date: Jan 2010
Posts: 55
NC

02-15-10, 01:19 PM   #1  
Sealing/insulating rim joists - slight confusion

I am evaluating how to best seal off gaps in my rim joists. We have a vented crawl space. Sealing the entire crawl space is currently not an option as we have a propane water heater and a propane furnace in there, neither one is of the direct-vent kind. Besides, it would be too big a job right now.

But I still want to prevent air coming through gaps in the rim joist area from going up the inside of the exterior walls. Is it sufficient to use some caulk/Great Stuff and seal any joints between the rim joists and the subfloor of the floor above, or do I need more?

Does putting insulation into the rim joist cavities make much sense in a vented crawl space? Would it reduce heat conductance into/out of the floor above? Likewise, should I seal the gaps between the sill plate and the wall?

What's the best way?

Thanks - MM

 
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Bud9051's Avatar
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ME

02-15-10, 02:39 PM   #2  
Hi MM. Well NC normally I would say you don't get a lot of cold, but this year you are getting blistered. If you are leaving the vents open, for combustion air, then it makes little sense to spend a lot of time sealing the rim to the foundation. Sealing all penetrations up into the house will help. I'll attach a link on air sealing in detail. With your furnace down there, that means some supply and return ducts. They also need sealing with duct mastic or foil tape. Then a good wrap of insulation.

Use a fire rated caulking or foam, Great Stuff or other. Sheet metal for larger gaps. Even sheetrock will work.

Review the link and let us know if you have questions.
http://www.efficiencyvermont.com/ste...ide_062507.pdf

Bud

 
xvimbi's Avatar
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Join Date: Jan 2010
Posts: 55
NC

02-15-10, 03:19 PM   #3  
Thanks, Bud. I must know this efficiencyvermont.com pamphlet by heart by now; I came across it in so many of your posts. I've gotten a lot of pointers from that document, but only a few of the depicted situations apply in our case. Thus my question.

The ducts in our crawl space and in the unconditioned attic (why do they do this? I guess it's sort of OK in NC) are all insulated already, so nothing much to do there. I'll just focus on hunting down holes, cracks and gaps.

Still quite a ways to go until I have turned our house into a passive house... $300 or less per year for heating, cooling and hot water sounds sooo enticing.

MM

 
Bud9051's Avatar
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02-15-10, 04:08 PM   #4  
I'll tell ya, the first time I talked to a home owner who was getting two seasons on a tank of oil, $200 per year at that time, I was sold, especially being an energy auditor. I had planned to improve my house, but decided to go super insulated and since I can do my own work, it really isn't that expensive. I'll be posting links showing the progress as soon as it is cleaned up enough for some good photos. Winter got in the way.

It always makes me feel good when others see the value in all of the information that is available on the web, thanks.

Bud

 
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