insulating the band joists

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Old 02-08-14, 08:39 PM
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insulating the band joists

hi folks,

new to the forum here with some questions.

I had a home energy audit performed a few days ago and as I suspected, they recommended insulating the band joists.

They're saying they can do it for just under $1,800. I'd rather do it myself and save a boat load of money.

That said, I'm looking for opinions on what is the best method to insulate my band joists when it appears as though the sill plate is flush with the block foundation. I believe the previous owner(s) of my house tried to put some brick inside the cavity and cement over it to I guess help insulate, though I'm not sure.

Should I run a bead of caulk around the inside of the band joists and then glue some rigid foam inside the cavity and then seal around the edges with expanding foam?!

Here's some photos that I hope help:











 
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Old 02-09-14, 04:47 AM
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Hi andrew and welcome to the forum.
This may help with the pictures:
http://www.doityourself.com/forum/el...-pictures.html
One consideration not often mentioned is a termite inspection. In areas where they are a major problem the codes require access to the entire rim joist. Whether that is required or not, the solution works fine and may be easier than the "cut and cobble" approach. That term is from The Energy Nerd at GBA.

There are two objectives, air seal and insulate. To provide the air sealing a good caulking will last a lifetime. You can also use your personal multi tools (fingers) as required. Can foam is a definite "no touch" product until it dries. Contractors prefer the can or spray foam because it is faster, but there are issues later on with expansion and contraction.

For insulation, Roxul has become a go-to product. It fits snug and can be removed and replaced if needed. Along with the rim joist you should add a good layer of insulation down the concrete wall as well. If memory serves me, an 8" concrete wall has an r-value of 1. New energy codes (not adopted everywhere) are requiring floor to ceiling r-10 or r-15 in most cold locations. That's 2 to 3 inches of rigid foam. Where cost is an issue, covering the inside of any concrete where the outside is exposed to the elements, plus 1 foot below grade wit even 1" of rigid will make a huge difference.

Bud
 
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Old 02-09-14, 05:52 AM
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Andrew, can you tell me what is the construction of your house? By that I mean the exterior finish, the foundation, maybe include a few other pictures?

What was the auditing firm going to do to insulate? I find it hard to believe that it could be $ 1,800.00.

The appearance I see from your other pictures seems to indicate that there are pieces of blocking inserted between the joists rather than a more typical continuous rim. Something is not making sense based on what I see. Also how old is the structure?
 
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Old 02-09-14, 06:14 AM
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Looks to me like it is a balloon framed house and they used brick to fill in the gap under the rim joist.
Balloon framing - Bing Images
 
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Old 02-09-14, 06:51 AM
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Bricks between joists were common in balloon framed houses. They also serve as blocking. While air sealing with rigid foam and caulk is a good place to start, I agree with Bud that insulating the entire exterior wall ought to be considered. Insulating just the rim area between your joists is pretty pointless when you have so much cold exterior wall that is also uninsulated. Covering the entire wall with rigid foam that is air sealed, then framing up a 2x4 wall in front of that would allow you to get the most r-value from floor to ceiling.
 
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Old 02-09-14, 09:22 AM
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The foundation is block and I'm pretty certain a large majority of the rest of the house is brick.

my house has siding from the 1st floor up, so judging from my neighbors house (exact same layout as mine) where she hasn't stuccoed, her first floor is brick and then I'm not sure about the upstairs as that's stuccoed.
 
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Old 02-09-14, 04:31 PM
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Ok, so I'm going to assume that the floor joists don't have a rim or box assembly, they run directly into the masonry that comprises the foundation and 1st fl wall assembly.

If this is the case then you have to be careful about what you do with insulation. Consideration has to be given to the brick and the way the building deals with ground surface water and the water shedding characteristics of the exterior finish.

Masonry walls that get wet have to dry but that process can be accomplished by drying to the interior of the structure and the exterior. If you install an insulation on the interior walls that is vapor IMPERMEABLE, you may very we'll drive moisture upward in the wall and create a situation that results in decay in the ends of the floor joists. It can also push the drying process entirely to the outside which, DEPENDING on certain other factors can result in deterioration of the masonry on the exterior.

Can you explain why the auditing firm thought it was critical to insulate the rim joists or what you are describing as the rim?

Is the interior finish on the levels above plaster directly on brick or is the brick structure furred out and then a lath and plaster applied?
 

Last edited by calvert; 02-09-14 at 04:54 PM.
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Old 02-09-14, 08:04 PM
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I think my best bet is going to be to check my neighbors basement to see if where the floor joists and foundation meet is open or not, then take photos for everyone to see.
 
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