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insulating above sill plate


sparky67's Avatar
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01-08-09, 09:14 PM   #1  
insulating above sill plate

Looking at my basement i think i should insulate above the sill plate between the floor beams. This is an unfinished basement and i am just trying too keep the first floor warmer. The question is what type of insulation? I don't want to Sheetrock the whole ceiling just becouse i added some insulation at the ends. Also is this worth it if i am not insulating the block?

 
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01-09-09, 05:27 AM   #2  
Hi sparky, there are two issues, the heat loss through the uninsulated surfaces and the air leaks between the wood and foundation and often the wood to wood seams. Even when you can't feel a draft, often air is still able to seep through. A quick bead of caulking will assure everything is tight, I like construction adhesive as it is cheap and dries tough, but just about anything works.

Once the sill plate and rim joist is all sealed, then a simple fill with fiberglass insulation will add the r-value you want. You can make the outer surface kraft, block with a layer of rigid foam, or anything to slow the air infiltrating in and out of the insulation. Some folks simple cut and fit rigid foam and glue in place for the entire job.

If you want an inexpensive foundation cover that I'm currently testing, send me a private message. I will eventually post my results once I have the Infrared pictures to support my efforts, but you may want to try it.

And yes it is worth it to do just the rim, but the block is another big looser.

Bud

 
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01-09-09, 08:29 AM   #3  
I just did this and my kitchen floor is almost as warm as the air on the first floor. I used the spray foam insulation in some spots b/c the sill plate didn't cover the holes in the cinder block. (house built in 1940's) I then caulked everything and used R-13 rolled faced fiberglass. I know I may not have need the faced(paper back) but it worked nice for stapling and lowes was offering it on sale of 8.98 for a 50' roll of it. It makes a difference even if you don't do your walls. I had a lot of air leaking in. Good Luck!

 
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01-09-09, 04:44 PM   #4  
I thouhgt some types of insulation could only be instaled if they were covered with a fire rated material? I will be replacing my boiler in a few months and I dont want the inspector to find other things to complain about.

 
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01-09-09, 05:12 PM   #5  
You are correct, some types can be an issue. But determining which ones and where is difficult as it is often up to the local inspector. The foil facing on some rigid insulations will have some benefit as a fire barrier, but I can't say for sure your inspector will approve it.

You can go with air sealing and just the fiberglass insulation and a final layer of kraft faced to cover the surface.

Bud

 
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01-09-09, 05:24 PM   #6  
Here's what I did.

I took a bunch of photos and wrote about the job I did insulating and sealing the sills. Here's the link: Dover Projects: How to Insulate Basement Rim Joists

The rigid foam says this on it, "Local building codes may require a protective or thermal barrier. For more information, consult MSDS, call Dow at 1-866-583-BLUE (2583)."

--Peter

 
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01-10-09, 06:50 AM   #7  
Acually, now that I've done a bit more searching around, it appears that Thermax™ might be a better rigid foam to use than what I used, as I think the Thermax™ Heavy Duty stuff doesn't need to be covered with drywall to meet code.

Here's what they say on the Dow site, "THERMAX™ Heavy Duty Insulation can be installed exposed to the interior without a thermal barrier"

Here's the link to all their Polyisocyanurate boards so you can pick the right now. I'm not qualified to pick it for you.

 
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