# Basement finishing insulation?



## Mml665 (Nov 30, 2015)

Anyone?


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## joecaption (Nov 30, 2011)

There has to be at least 2000 post on this same subject, tried using the search funtion?
Huge mistake trying to address this on the inside.
99% of the time any moisture issues needs to be addressed from the outside.


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## Mml665 (Nov 30, 2015)

Joecaption there has no longer been evidence of moisture. I am leaning toward the fact that the previous owner a widow was taken advantage of with the installation of the French drain. Also I did use the search function, there is so much variance among the existing threads in one thread it will be said oh yeah pink XPS is fine, next thing use blue foam board, then someone mentions foil. That is why I decided to start a new thread with the facts that pertain to my basement and home state of Michigan. Thank you for your input


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## bmathews (Sep 22, 2015)

http://buildingscience.com/documents/information-sheets/basement-insulation


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## Gary in WA (Mar 11, 2009)

Welcome to the forums!

Just answered one similar from same place (State anyhow); http://www.diychatroom.com/f15/alternative-drylok-345594/ lol.

Gary
PS use foil-faced fb on rims after caulking joints; Read my *#6 and #10 *here; http://www.diychatroom.com/f103/insulate-rim-joists-canned-spray-foam-roxul-307313/ Use fb under the plate-non-PT with f-facing to stop air/moisture/thermal better than low R-2 or so; sill sealer.


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## Mml665 (Nov 30, 2015)

Gary in WA said:


> Welcome to the forums!
> 
> Just answered one similar from same place (State anyhow); http://www.diychatroom.com/f15/alternative-drylok-345594/ lol.
> 
> ...



Gary, the foil faced fb you mention is that the pink, blue, or the actual blue foil with a yellowish foam board sandwiched between two layers of the foil. Now that I think of it some of the pink fb has a plastic sheet layer as well. For the rim joist a local hardware store recommends the pink 2" foam board then a fiberglass with paper following that. Hence my confusion and apprehension. I appreciate your info, I am on overload lol


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## Windows on Wash (Aug 30, 2011)

Many of the foil faced foams will be of the Polyiso variety but you can get it in either foam. 

The foil makes is a Class I vapor retarder and slows the radiant energy movement. 

The foil will replace the necessity for any additional vapor migration control.


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## Mml665 (Nov 30, 2015)

Windows on Wash said:


> Many of the foil faced foams will be of the Polyiso variety but you can get it in either foam.
> 
> The foil makes is a Class I vapor retarder and slows the radiant energy movement.
> 
> The foil will replace the necessity for any additional vapor migration control.



So does the actual color of the foam board make a difference the thinner pink foam board has a clear plastic sheet on it, the 2" does not, there is a version the blue board as well that had the plastic, then there is the bluefish foil that has a yellowish core. Hence my confusion and reasoning for posting this thread. I appreciate the info everyone provides.


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## Windows on Wash (Aug 30, 2011)

The facing and type of foam determine vapor permeance.


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## Mml665 (Nov 30, 2015)

So which foam board insultation would be appropriate for the rim joist/bond area, and which would be good for the cinder block foundation wall?


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## throrope (Oct 30, 2015)

We have a concrete foundation and finished our basement several years ago.

Basement walls are a heat sink and you could be seeing condensation from the air and not moisture coming through the wall.

I got a roll of six mill plastic, wrapped it on a furring strip and masonry screwed through the strip into the top of the concrete wall leaving the plastic to hang. I then 2x4 famed on top of the plastic that extended at the floor on 24" centers (non-bearing wall). Then put faced 24" wide 4" fiberglass insulation batts between the studs. The sill stud is pressure treated. I also covered the floor with 6 mill plastic taped with a specific tape by 3M rated for polyethylene. Over that went felt underlayment and clic type flooring.


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## Mml665 (Nov 30, 2015)

I was thinking of using this in the final joist area sealed with canned spray foam around the edges.
http://m.homedepot.com/p/Owens-Corn...uared-Edge-Insulation-Sheathing-45W/100320352

Then I was considering this product for the cinder block wall surface of the foundation.
http://m.homedepot.com/p/Owens-Corn...nd-Groove-Insulation-Sheathing-68WD/100320355

I also visited the lowes web site they offer a light greenish blue product with the same specs, hence my confusion and apprehension regarding the insulation project


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## Mml665 (Nov 30, 2015)

I also wanted to add the basement is below grade, the exterior of the house is brick. 
Also could anyone share their opinion on the Foamular products I mentioned in the post above, I was also considering Foamular 250 2" for the rim joist area followed with fiberglass with paper facing the interior. 
I may have been causing confusion by mentioning XPS in previous posts it is extruded polystyrene the Dow Foamular 150 & 250 are pink in color.


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## Windows on Wash (Aug 30, 2011)

XPS = Extruded polystyrene

For the rims, I would use foil faced like Gary mentions.


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## Alketi (Dec 20, 2015)

By foil-faced, I assume you're talking about a product like this:

http://www.homedepot.com/p/Super-TU...t-R-6-5-Insulating-Sheathing-268426/100322374

Double-faced poly-iso. But, isn't poly iso very bad at dealing with water? The foil-facing prevents a problem, but the narrow edges on each side will be unfaced.

So, would you recommend sealing the four unfaced edges with aluminum tape, for a continuous foil-barrier, before installing?


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## Mml665 (Nov 30, 2015)

Could someone offer a link to the foil faced product for the rim joist area, so as to clear up my confusion, thank you to all who participate in this thread


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## Alketi (Dec 20, 2015)

Mml665 said:


> Could someone offer a link to the foil faced product for the rim joist area, so as to clear up my confusion, thank you to all who participate in this thread


I linked a foil-faced polyiso, in the post just before yours. Home Depot carries it. Lowes, to my knowledge, does not.

However, polyiso (even foil faced) has a much higher water absorption percentage over XPS foam -- and especially if the foil deteriorates or is penetrated.










For foil-faced polyiso, I would, at least, think that sealing the four exposed edges with additional aluminum tape would be wise. 

And, I've also heard people recommend XPS over polyiso for these humid applications.


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## Windows on Wash (Aug 30, 2011)

Is this for an interior or exterior application? If it is interior, the absorption concern is moot. 

Isn't this interior foam?


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## Gary in WA (Mar 11, 2009)

Sorry if I caused any confusion. The rims should be faced foam- plastic, foil, anything with a low permanence to stop winter/summer moisture drives/condensation.


" However, especially in retrofit situations, the amount of exterior insulation that can be installed (if any) may not be sufficient to provide adequate thermal insulation (at least R-10). Thus in these cases, the alternative is to install rigid insulation (such as foil-faced polyisocyanurate) flush against the interior side of the sheathing. This still allows air drying of the rim joist cavity but *reduces the potential for interior summer condensation* by decreasing the condensation surface to the bare minimum of the interstices of the insulation/ sheathing interface. *In the winter, the insulation is protected from interior-sourced water vapor by the foil-facing."


* Granted, you wouldn't see a lot of condensation unless you added fibrous insulation in the floor cavity (directly inboard of the foam) to reduce the foam board temps there As that interface wouldn't be warmed by the room as much. 

More importantly is the facing on the rim side of the foam to stop any moisture from entering the foam to keep the wood wet longer, with more time to mold. The interior faced, if foil, would also support radiant heat resistance, a good thing- if 3/4" gap. Don't use any facing and you will still be waaay better than none at all. 

IMO, use a faced product on the walls as you have an interior drainage system and want to stop any moisture through the CMU to weep down and pump out. Poly will also work but *only *with a drainage system interior.

Gary


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