# Closed/Open cell foam applications 2 part question



## Windows on Wash (Aug 30, 2011)

You don't get near the listed yield from the 2 part kits and the foam is not as good as a professional reactor.

Spraying the underside of the roof deck can also be a disaster if you ever have to replace some sheathing.

I would put rigid foam in the rafter bays as that will get you a higher R-Value and will not require replacement if you ever have to service the roof.

Open cell on the roof is vapor open and you can get rot, mold, mildew on the underside of the sheathing if the layer is not thick enough and proper.

Are you going to be finishing with drywall?


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## JulesB (Jan 19, 2011)

*Re: closed/open*



Windows on Wash said:


> You don't get near the listed yield from the 2 part kits and the foam is not as good as a professional reactor.
> *I've not heard that.*
> 
> Spraying the underside of the roof deck can also be a disaster if you ever have to replace some sheathing.
> ...


Thanks for responding.


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## Windows on Wash (Aug 30, 2011)

Rigid board across the rafters because foam in between doesn't change the thermal bridging of the rafters.

I have heard the dry rot issue but I would be willing to bet that you will have condensation issues with open cell before dry rot with closed.


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## JulesB (Jan 19, 2011)

Windows on Wash said:


> Rigid board across the rafters because foam in between doesn't change the thermal bridging of the rafters.
> *Agreed. Though attic space is very tight with the air handler up there. Unable to get more than say 2' x 4' pieces installed. In some areas, I'd simply planned to "wrap" the rafters with spray foam. (assuming I could afford to)*
> 
> I have heard the dry rot issue but I would be willing to bet that you will have condensation issues with open cell before dry rot with closed.


*I tend to agree. *
*In my efforts to secure an insulator, I've taken 4 estimates, and spoken to several others (at recent home shows). And it's amazing how polarized the thinking is. Some will gladly shoot closed cell on the roof. Others absolutely will not.*


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## Canucker (May 5, 2011)

Dry rot is caused by elevated moisture. If you've airsealed the underside of the roof deck completely, wouldn't the only place for moisture to get in be a roof leak, provided the foam is thick enough?


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## Gary in WA (Mar 11, 2009)

Written just for you, LOL: http://www.buildingscience.com/documents/reports/rr-1001-moisture-safe-unvented-wood-roof-systems
Notice Table 3 and conclusions....

Tips: http://www.sprayfoam.com/newsarchives/archivedetails.cfm?id=123

Gary


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## JulesB (Jan 19, 2011)

Canucker said:


> Dry rot is caused by elevated moisture. If you've airsealed the underside of the roof deck completely, wouldn't the only place for moisture to get in be a roof leak, provided the foam is thick enough?


That's my understanding. Which is also considered to be problematic, as any leaks would potentially never get past the underside of the decking, since the closed cell would trap it.


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## JulesB (Jan 19, 2011)

GBR in WA said:


> Written just for you, LOL: http://www.buildingscience.com/documents/reports/rr-1001-moisture-safe-unvented-wood-roof-systems
> Notice Table 3 and conclusions....
> 
> Tips: http://www.sprayfoam.com/newsarchives/archivedetails.cfm?id=123
> ...


I do believe you're right. Written just for me.
Thanks for the link Gary!
Regards,
Jules


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## bf514921 (Jul 8, 2012)

I know you asked for diy'ers and the kits but i thought i would add one thing that hopefully helps. I had closed cell insulation installed yesterday in my basement. the one thing i did notice is the preasure at which they can install. With their setup they were able to install at a much higher pressure. shooting better into all the gaps andstuff.


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## JulesB (Jan 19, 2011)

bf514921 said:


> I know you asked for diy'ers and the kits but i thought i would add one thing that hopefully helps. I had closed cell insulation installed yesterday in my basement. the one thing i did notice is the preasure at which they can install. With their setup they were able to install at a much higher pressure. shooting better into all the gaps andstuff.


If I might ask. Did they bid the job on sq. footage? Or was it simply a blanket bid? 
In my case, three of the four didn't even account for the windows and doors. 29 windows and 4 doors, 2 of which are french double doors. On initial interviews, the so called going rate for the first inch of closed is around $2/ft. In may case, after you remove footage for doors and windows, the figure comes out more like $6-8/ft.
With those numbers, I can be less efficient for decades......


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## bf514921 (Jul 8, 2012)

no i only had 1 small window. I also had the box sill hit with 3inches of closed cell instead of 2, like the rest of the basement. you must have a TON of windows and doors, very cool.


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## bf514921 (Jul 8, 2012)

only thin gi can think of is windows and doors are obstacle to go around mask off protect, that may have something to do with it. i am guessing as with alot of thinks the majority of the cost is not in materiel, but in labor.


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## bf514921 (Jul 8, 2012)

i think mine cost was around 2.30 for everything, 3 inch in box sill and 2 inches in walls, it was around 580 sq feet total, blaket bit, but i only had 1 small window.


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## JulesB (Jan 19, 2011)

bf514921 said:


> i think mine cost was around 2.30 for everything, 3 inch in box sill and 2 inches in walls, it was around 580 sq feet total, blaket bit, but i only had 1 small window.


 
Well that's reasonable enough.


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