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Old 01-30-2014, 12:39 AM   #16
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Basement Insulation Question ?


I don't think so Gary ... I greatly appreciate you taking the time to provide this information. I was going to post a few pictures of the foundation walls and the wood framing, but I don't think the pictures add much value.

Since I'm planning on using the existing framing, the amount and type of insulation will vary in different areas of the basement. In some areas the wood frame is nailed directly to the foundation wall and there is a 1" cavity between that wood to add foam board. In other areas there is a wood frame 6" from the wall which could support both foam board and fibrous insulation, but as you indicated above, this reduces the effectiveness of the foam board. There are some other scenarios down there too, but ultimately I think every wall should be able to get foam board coverage. I'll have to read up on combining fibrous w/FB.

Thanks again!

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Old 01-30-2014, 05:10 PM   #17
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Basement Insulation Question ?


Even 1" XPS unfaced is better than just cavity fill. Piece-meal it in if needed, canned foam between the joints and under perimeter; it requires completely air-tight installation. Taping the joints will work short term but as the fb ages, it shrinks- breaking the bond between the two pieces; allowing air entry for condensation on cold concrete wall. Even the adhesive should be applied in 1' square grid patterns to limit air movement if compromised by any 1/16" gaps anywhere; http://joneakes.com/jons-fixit-database/743 Where the frame wall is close to concrete, even 1/2"XPS, then add XPS between the studs- then compress cavity fill to meet minimum thickness is fine.http://numsum.com/spreadsheet/show/21111

Canned foam/XPS the rims, after caulking the joints touching the rim joist; to sheathing/decking above, to mudsill plate. Any cavity between colder concrete wall/fibrous insulation will allow/have convective loops; robbing you of R-value and creating a chase open for fire travel behind the wall. An outlet fire could easily run horizontally to travel vertically up the wall and into a floor joist cavity, across that to and up a plumbing chase/space around pipe; to the attic (air seal all top plate penetrations) and catch the roof framing on fire--- burning the house both down/up at the same time. http://publicecodes.cyberregs.com/ic...002_par017.htm

http://www.buildingscience.com/docum...a-foam-shrinks

My point was; use code required R-value fibrous insulation to meet code after FB insulation used, don't add more than required cavity fill to lower dew-point at foam. Fig. 3-6; adding cavity fill R-value reduces FB dew-point temps; http://www.buildingscience.com/docum...nsulation/view
Check with your local AHJ.

Gary
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Last edited by Gary in WA; 01-30-2014 at 05:18 PM. Reason: added link.
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Old 01-30-2014, 10:06 PM   #18
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Basement Insulation Question ?


I'm sure I'm not the only one who appreciates the level of detail you're providing. This is great info.

From what I can see, the highest R-Value FB insulation is about R5 ... Does that sound right? In areas where I have a large cavity I will use both, but there are areas of the basement where I will not be able to achieve the R-value without adding some wood framing for fibrous insulation. In those areas I was planning on using the highest R-Value FB that will fit between the 1" framing that's on the concrete.
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Old 01-31-2014, 12:46 AM   #19
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Basement Insulation Question ?


PIC is R-6.5 (aged) though the air sealing of it requires impeccable. http://www.buildingscience.com/docum...r_code_changes

The framing is usually for the required wiring. You could also cut FB for between the studs, just be sure it is glued to the FB on the concrete wall. PIC (foil-faced polyiso) or PIR;http://www.buildingscience.com/docum...roperty-table/

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Old 01-31-2014, 03:00 PM   #20
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Basement Insulation Question ?


Lots of very good info here and I'm putting my two bits in too.

Very first thing, make sure you have a dry basement........everyone here knows this anyways.

Best and most expensive way......spray foam applied between the studs, just like you see on Holmes on Homes and a few other shows.

Second best and second most expensive way........Styrofoam SM installed between the studs. Gaps around boxes and along the framing need to be sealed with cans of XPS non-expanding foam.
Windows...... you mentioned using a Styrofoam glue for attaching the panels to the concrete.......there is a better way, use plastic anchors and a hammer drill.


The cheapest and most common way.......and the one that causes the most confusion.
- fiberglass insulation.
The problem with fiberglass is it likes to soak up water so don't use this if you think there's the potential of a wet or damp basement.
There's been lot's of people do this a lot of different ways and it has evolved several times.

I think the best way is...... first make sure your wall studs are about 1" or more from the concrete wall and the bottom plate is sitting on sill gasket.........you should do this no matter which insulating method you use.
If your using fiberglass insulation you want ventilation between the insulation and the concrete wall anyways.

Next you should make sure the fiberglass bats can not come in contact with the concrete, best way to do this is apply exterior building wrap like Typar on the back side of the stud wall........this allows the insulation to breath and stay dry.
The vapor barrier then goes on the front side (warm side) of the wall and insulation.

Last edited by Gary Evans; 01-31-2014 at 03:12 PM.
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Old 02-02-2014, 12:50 AM   #21
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Basement Insulation Question ?


Sorry...don't mean to kill your post here but I recently bought a house and the basement is insulated the way Gary just described as the most common way.

Here is my post Renovating basement and insulation..gut job or keeper.. .
I would love if you guys commented and Gary since you describe the common way to insulate, tell me if it's a keeper or not.

Thanks
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Old 02-03-2014, 09:49 PM   #22
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Basement Insulation Question ?


Yes, I'll stick my neck out here and say that doing it the way I described is a keeper.

It's not the very best way but the most practical way if your on a budget......and better than at least 3/4 of the homes out there.

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