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Author	Comments
Scott Plantier Posted: Apr 05, 2011 05:05 PM	Spraying an attic in reverse. I'm going to spray rafters from above when roof sheathing is removed. I'll be spraying down onto the backside of the old plaster and lathe making the plaster very secure but what do you think of putting 3" of 2# TOPPED by 3" of FG to the upper edges of the rafters? Won't it be 100% certain not to have any interior moisture drive into the FG? It'll drop my bf by 1200 too. Wait, that moisture drive goes both ways depending on the season right? We have about 5400 degree days here to give you an idea of the heat load in western Massachusetts.
Craig Gifford Posted: Apr 05, 2011 05:23 PM	You may be trapping moisture between the foam & the new deck sheathing which may eventually degrade the new deck sheathing...just my humble opinion. If this is the way you are going I would recommend some form of ventilation in the space above the spray foam and below the new roof sheathing (the 3" occupied by fiberglass). What part of Western Mass?
Scott Plantier Posted: Apr 05, 2011 06:17 PM	Thanks for the pointer. I'm in Pittsfield on the NY border. Ventilation would not work with the roof as it is designed so I will spray it solid.
Circle-D Posted: Apr 05, 2011 08:32 PM	Spray it solid or not, you are still going to have air gap. Whether is is 3" or .003" won't you will still have a surface (underside of roof deck) for condensation to form on? I did this to my house 2 summers ago. Sprayed 5" down onto my interior roof (ceiling) and left 4.25" open for ventilation. Works like a charm, 25% savings just from doing the roof cavity.
Scott Plantier Posted: Apr 05, 2011 11:29 PM	It's a 5 1/2 space and if sprayed full of 2# there'll be no possibility of moisture drive from inside the warm moist house all winter long. Summer does not see us using A/C here so the reverse drive into the space you mention is not a concern but still has caused me to forget about using a combo of FG and the 2#
Scott Plantier Posted: Apr 06, 2011 07:41 PM	Skip, I shouldn't say the outside of the sprayed bay is not a concern-I don't know that to be true just think it is not a problem!
Craig Gifford Posted: Apr 06, 2011 08:15 PM	Wow, I am only 30 minutes to the North, in North Adams....what is the name of your company!
Scott Plantier Posted: Apr 09, 2011 03:26 PM	It is just me and subs repairing an old victorian in Pittsfield on Clinton Ave. Have some chimney, full roof and siding work to do!!

Author

Comments

Scott Plantier

Posted: Apr 05, 2011 05:05 PM

Spraying an attic in reverse.

I'm going to spray rafters from above when roof sheathing is removed. I'll be spraying down onto the backside of the old plaster and lathe making the plaster very secure but what do you think of putting 3" of 2# TOPPED by 3" of FG to the upper edges of the rafters? Won't it be 100% certain not to have any interior moisture drive into the FG? It'll drop my bf by 1200 too. Wait, that moisture drive goes both ways depending on the season right? We have about 5400 degree days here to give you an idea of the heat load in western Massachusetts.

Craig Gifford

Posted: Apr 05, 2011 05:23 PM

You may be trapping moisture between the foam & the new deck sheathing which may eventually degrade the new deck sheathing...just my humble opinion. If this is the way you are going I would recommend some form of ventilation in the space above the spray foam and below the new roof sheathing (the 3" occupied by fiberglass).

What part of Western Mass?

Scott Plantier

Posted: Apr 05, 2011 06:17 PM

Thanks for the pointer. I'm in Pittsfield on the NY border. Ventilation would not work with the roof as it is designed so I will spray it solid.

Circle-D

Posted: Apr 05, 2011 08:32 PM

Spray it solid or not, you are still going to have air gap. Whether is is 3" or .003" won't you will still have a surface (underside of roof deck) for condensation to form on?
I did this to my house 2 summers ago. Sprayed 5" down onto my interior roof (ceiling) and left 4.25" open for ventilation. Works like a charm, 25% savings just from doing the roof cavity.

Scott Plantier

Posted: Apr 05, 2011 11:29 PM

It's a 5 1/2 space and if sprayed full of 2# there'll be no possibility of moisture drive from inside the warm moist house all winter long. Summer does not see us using A/C here so the reverse drive into the space you mention is not a concern but still has caused me to forget about using a combo of FG and the 2#

Scott Plantier

Posted: Apr 06, 2011 07:41 PM

Skip,

I shouldn't say the outside of the sprayed bay is not a concern-I don't know that to be true just think it is not a problem!

Craig Gifford

Posted: Apr 06, 2011 08:15 PM

Wow, I am only 30 minutes to the North, in North Adams....what is the name of your company!

Scott Plantier

Posted: Apr 09, 2011 03:26 PM

It is just me and subs repairing an old victorian in Pittsfield on Clinton Ave.

Have some chimney, full roof and siding work to do!!

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