dolphin
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| 11/03/2009 4:24 PM |
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I was wondering if Polyisocyanate (Foil backed yellow foam insulation) was appropriate for use to insulate the foundation of a finished basement? The advertised R value of 6.5/inch and the price for factory seconds, 4 x 8 sheets (1" - $8, 2" - $12.50) seem very attractive... if allowable. If this is not appropriate for use in a basement, then where would/could such a product be used?
Here are some photos.
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Dana1
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| 11/03/2009 5:29 PM |
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In a foundation it can be used for anything above grade (down to maybe a couple feet below grade), but the facing is vapor impermeable, and there can sometimes be issues if the below grade portion of the foundation can't dry toward the interior, saturating the concrete and forcing the ground moisture up. If there's sufficient above grade exposure on the exterior of the foundation that it dries fully toward the exterior, fine- the worst that can happen is a bit of efflorescence & spalling (which can be mitiated with a layer of sacrificial parging.) If it drives moisture into the sill, rot can occur.
Under no circumstances should you apply this to interior side of a sub-grade studwall- the studs will have mold & rot issues. The insulation is best mounted against the concrete, held in place with furring or an interior side studwall though. If using furring, through-screw it to the foundation, and screw the gypsum (1/2" minimum, required by code as thermal barrier for foam insulation, including foil-faced iso) to the furring. Tape,caulk or otherwise air-seal all seams at the interior facing. If using multiple layers of the foil faced stuff, staggering the seams on the layers, then sealing the interior layer would be sufficient.
It's definitely "right-priced". If you do the upper half of the foundation with 3-4" of iso, you can do just fine with 3-4" of (much cheaper, lower-R, but very permeable) EPS bead-board with only a small hit in performance, since it's unlikely you'll see sub-freezing temps all the way down to the slab level in hour location.
This stuff is often used for insulating walls (including masonry walls), sometimes roofs. It's high performance stuff, but easy to damage in handling, definitly not for use under slabs, etc. |
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dolphin
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| 11/04/2009 8:10 AM |
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| Could you use this in a rafter application, placed within the cavity, with a 2inch space for the air to circulate under the roof/sheathing? Also, am I to understand that this would be ok to use in an interior wall application within the stud cavity (vinyl siding - house wrap - OSB - foil faced insulation within a stud wall - drywall)? I am thinking about using it in the walls of a bonus room above a garage. |
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Dana1
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| 11/04/2009 9:29 AM |
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Posted By dolphin on 11/04/2009 8:10 AM
Could you use this in a rafter application, placed within the cavity, with a 2inch space for the air to circulate under the roof/sheathing? Also, am I to understand that this would be ok to use in an interior wall application within the stud cavity (vinyl siding - house wrap - OSB - foil faced insulation within a stud wall - drywall)? I am thinking about using it in the walls of a bonus room above a garage.
If placed whereever you would place a Class-I vapor retarder it's good- but be careful.
In the rafter & wall cavities it's good, but wedged between the interior gypsum and the rafter or studs to form a thermal break for the framing is even better. A 1" layer over a 2x6" stud more than doubles the R-value at that point. A 1" layer over a 2x4" stud triples the R-value of the stud.
The cumulative effect of those thermal breaks on clear-wall & whole wall R-values is huge, which is why R5 XPS sheathing gets such mileage. It doesn't matter if that break happens on the interior, the exterior, or both- framing timbers are just lousy from an insulation POV, and it doesn't take much thermal break to make huge improvement.
Cutting them down for cavity insulation is tedious and the fit guaranteed to be imperfect, so foam-sealing the edges is required to prevent convection currents within the cavity. In your location just be sure of 2 things:
A: It's installed on the conditioned-space side of the assembly (the warm-in-winter, interior side)
B: There are no other Class-I vapor retarders in the assembly (an issue with some unvented roofs.)
When used in this fashion, sealing the seams with FSK tape, and foam-sealing around plumbing & electrical penetrations makes it a very effective air & vapor barrier. If there are any dings on the interior side facer, patching them with FSK tape before the gypsum goes up is a good idea too.
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aardvarcus
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| 11/04/2009 4:40 PM |
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| May I ask what company you found that carries that insulation and where it is located? I am in Tennessee, but I am going to need quite a bit of it (300+ sheets of the 2") in the next year or so. |
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dolphin
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| 11/04/2009 6:57 PM |
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| Sure! I found it at a website called insulationfactoryseconds.com. I am going to call them again tomorrow to see if they have any of the polyiso product WITHOUT the foil. I am assuming that it is the foil that makes this product a Class I vapor barrier and that WITHOUT the foil, it would perform like XPS. Please correct me if that is the wrong assumption. |
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richm
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| 11/04/2009 9:10 PM |
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Aardvarcus and Dolphin,
Check out www.insulationdepot.com; I have read on this site that there is a distribution center in TN. If you Google "recycled board insulation" you will find others.
richm |
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Dana1
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| 11/05/2009 7:58 AM |
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Posted By dolphin on 11/04/2009 6:57 PM
Sure! I found it at a website called insulationfactoryseconds.com. I am going to call them again tomorrow to see if they have any of the polyiso product WITHOUT the foil. I am assuming that it is the foil that makes this product a Class I vapor barrier and that WITHOUT the foil, it would perform like XPS. Please correct me if that is the wrong assumption.
Without facers iso is highly vapor-permeable- more permeable than EPS, but has K & R values higher than XPS, (comparable to 2lb polyurethane foam but far more permeable, and with a higher temp rating.) Iso is also sold with highly permeable fiber-facers, usually marketed as roof insulation.
With the foil, it's a Class-I vapor retarder.
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aardvarcus
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| 11/05/2009 3:37 PM |
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| You could always poke holes in the foil facing. Using a 2'*2' piece of plywood with nails poking 1/4" out the bottom and a handle on top, a person could quickly remove parts of the vapor barrier. By adjusing the # of nails, you could actually fine tune the permiability you wanted. |
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Dana1
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| 11/05/2009 4:49 PM |
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Posted By aardvarcus on 11/05/2009 3:37 PM
You could always poke holes in the foil facing. Using a 2'*2' piece of plywood with nails poking 1/4" out the bottom and a handle on top, a person could quickly remove parts of the vapor barrier. By adjusing the # of nails, you could actually fine tune the permiability you wanted.
A roller type mechanism would probably be easier to use, but this would work.
Perforated radiant barrier typically has tiny holes on a 1/2" or 3/4" grid, which would probably be the right way to go here if you wanted to use the same stuff below grade. (Don't forget to rework both the interior & exterior facers.)
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dolphin
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| 11/06/2009 9:39 AM |
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| Great information. The insulationfactoryseconds does have one inch ISO with the fiber mesh as a facing instead of the foil. If I understand everything (I am a physician, so this is all new... but very interesting), I can use the 1 inch ISO ($8/board!) for the basement with a studwall against it and fiberglass within the cavity. I can use the foil faced ISO in the attic and along the rafters in the bonus room as well as any above grade wall. I am planning on using it in the garage walls and the attic and bonus room. As per the recommendations on this thread, I will tape between the sheets, directly over the studs with foil tape to try and get this application as air tight as possible. Am I making sense? |
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Dana1
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| 11/06/2009 3:58 PM |
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Posted By dolphin on 11/06/2009 9:39 AM
Great information. The insulationfactoryseconds does have one inch ISO with the fiber mesh as a facing instead of the foil. If I understand everything (I am a physician, so this is all new... but very interesting), I can use the 1 inch ISO ($8/board!) for the basement with a studwall against it and fiberglass within the cavity. I can use the foil faced ISO in the attic and along the rafters in the bonus room as well as any above grade wall. I am planning on using it in the garage walls and the attic and bonus room. As per the recommendations on this thread, I will tape between the sheets, directly over the studs with foil tape to try and get this application as air tight as possible. Am I making sense?
The 1 inch fiber faced stuff is good for R6-6.5-ish. At $8/sheet that's 25cents/square foot, and you get the full R value out of it. If you went with 3 overlapped layers it'd be a true R20-21 for 75cents/foot. Is fiberglass SO much cheaper?
You'd have to go to R15 batts in a 24" o.c. studwall to match that whole-wall performance, and it would be an 1.2-1" thicker wall overall. The only advantage to the studwall would be not having to surface-mount the electrical outlets, etc. (which could arguably be cut into the iso, if so inclined.)
If they had 2-3" fiber faced goods at $20-25/sheet the labor would be lower, but double or triple-lapping 1" isn't bad. Several blobs of foam-board adhesive will get the first course stick to the wall, and some fairly thin striping of adhesive is good for the following courses, over which furring strips can be added (through-screwed to the foundation) for mounting the sheet rock. You can't just glue the sheet rock to the iso- the glue will fail under heat, defeating the gypsum's thermal/ignition barrier function- it has to be screwed into something more solid (like furring that is mechanically fastened to the foundation.)
It sounds like you understand the proper placement of the foil, and the importance of air-sealing it when you do. (Well ahead of half the home building contractors I've encountered in the past decade! :-) )
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dolphin
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| 11/07/2009 8:49 AM |
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| Have you ever heard of ISO with a black facing? Is that also a Class I or II vapor barrier? I found another source with a location that is favorable for me. Thanks. |
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Dana1
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| 11/09/2009 5:05 PM |
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Posted By dolphin on 11/07/2009 8:49 AM
Have you ever heard of ISO with a black facing? Is that also a Class I or II vapor barrier? I found another source with a location that is favorable for me. Thanks.
Ask 'em what it is, and what it's permeability rating is. There is a lot of iso in various form sold as roofing insulation, some will work fine in basements, others not.
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