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Author	Comments
John Kalinich Posted: Jul 18, 2007 04:25 PM	Prep to Insulate Wall & Cieling I am doing prep to have wall and cieling foam insulated. Wall has a "crawl space" between it and roof (barn style) and attic has very little headroom so best to spray from below. Without wallboard or plywood to spray the foam against, what could be used. Tyvec? Plastic sheet? Rosin paper?
mason Posted: Jul 18, 2007 05:21 PM	Please be a little more specific. I am not grasping the application. I presume there is a substrate to spray the foam to, either the floor of the attic or the underside of the roof deck. Where would the Tyvek, plastic sheet or rosin paper be located?
Tim O'Keefe Posted: Jul 19, 2007 12:08 AM	Are you talking about the spraying the kneewalls? If so you could install tyvek from the backside and spray against that. If you install it from the front and spray against it from the back it could bulge out and make installation of the drywall difficult. Don't use plastic, as the foam will not adhere very well to that. If that is not what you are talking about...forget what I said! Tim Granite State Spray Foam Co.
John Kalinich Posted: Jul 19, 2007 07:53 AM	Yes I am talking about knee wall (although it is 9' tall). behind will be unheated crawl space over roof overhang. Also the joists will not have "flooring" applied in attic space ao again, nothing to sptay onto. Assume using Tyvec as "floor" in attic would allow spray to adhear and then cover room (walls and cieling) with wall board after insulating. Picture: wall at left is knee wall http://www.xcix.net/plumb/pix1.jpg
mason Posted: Jul 19, 2007 02:43 PM	The picture did not come through, but if you are talking about spraying a 9 foot high wall with only Tyvek as the substrate, the foam is not strong enough by itself to hold up. Is there anyway to make a structural framework to reinforce it?
philip mullins Posted: Jul 19, 2007 06:57 PM	i think he is saying that he wants to spray from inside the room and then install sheetrock. if i were tryin to do that i believe i would buy some luan or cheap particle board just to be safe. but, you could prob get away with a heavy duty tarp and good staples. just depends on how much $ ur tryin to save. what i dont get is if you can get in there to install tyveck, why cant you get in there to spray?
John Kalinich Posted: Jul 19, 2007 08:23 PM	OK found a better picture, see link. My original goal was to find a material to spray the foam against that would "breath" but I guess the foam is actually a vapor barrier making this much less important. My next thought was that the insulation would become self supporting once hardened. Spraying kneewall onto back of sheetrock from behind is possible, but, cramped quarters would make for a less than happy installer. Since I am hearing that there is not really a good solution with a "film" material I'm guessing the cost of luan, PB or even plasterboard may be what it takes to do the job right. A couple new things... There is a small section of transition between knee wall and cieling where I think there should be venting between the roof and insulation to allow flow from behind knee wall to attic. Had thought about using the fiberglass panels made for this in these areas. Then spray foam on them. Finally a solid material might be the best protection against the occasional mouse or two that visit (this is vacation cabin that is not occupied all the time). Thanks for all your help!
Tim O'Keefe Posted: Jul 19, 2007 09:33 PM	Unless this is an extremely steep pitched roof, a 9' kneewall should allow more than sufficient room for an installer to spray foam from behind onto drywall or other finished wall material. Tim Granite State Spray Foam Co.
John Shockney Posted: Jul 19, 2007 10:32 PM	After looking at your picture I would recomend spraying the under side of the roof and use the closed (conditioned) attic system. thanks Airpro
Thomas Kasper Posted: Jul 19, 2007 11:16 PM	I wouldn't spray the knee wall. I'd spray the roof deck. IF possible I'd spray down on the ceiling after the drywall if installed.
Gerry Wagoner Posted: Jul 20, 2007 04:22 PM	You can install luan board, or cardboard or insulweb fabric and spray to any one of those. Done it many times... Best wishes, olger

Author

Comments

John Kalinich

Posted: Jul 18, 2007 04:25 PM

Prep to Insulate Wall & Cieling

I am doing prep to have wall and cieling foam insulated. Wall has a "crawl space" between it and roof (barn style) and attic has very little headroom so best to spray from below.

Without wallboard or plywood to spray the foam against, what could be used. Tyvec? Plastic sheet? Rosin paper?

mason

Posted: Jul 18, 2007 05:21 PM

Please be a little more specific. I am not grasping the application. I presume there is a substrate to spray the foam to, either the floor of the attic or the underside of the roof deck. Where would the Tyvek, plastic sheet or rosin paper be located?

Tim O'Keefe

Posted: Jul 19, 2007 12:08 AM

Are you talking about the spraying the kneewalls?

If so you could install tyvek from the backside and spray against that. If you install it from the front and spray against it from the back it could bulge out and make installation of the drywall difficult.

Don't use plastic, as the foam will not adhere very well to that.

If that is not what you are talking about...forget what I said!

Tim
Granite State Spray Foam Co.

John Kalinich

Posted: Jul 19, 2007 07:53 AM

Yes I am talking about knee wall (although it is 9' tall). behind will be unheated crawl space over roof overhang. Also the joists will not have "flooring" applied in attic space ao again, nothing to sptay onto. Assume using Tyvec as "floor" in attic would allow spray to adhear and then cover room (walls and cieling) with wall board after insulating.

Picture: wall at left is knee wall
http://www.xcix.net/plumb/pix1.jpg

mason

Posted: Jul 19, 2007 02:43 PM

The picture did not come through, but if you are talking about spraying a 9 foot high wall with only Tyvek as the substrate, the foam is not strong enough by itself to hold up. Is there anyway to make a structural framework to reinforce it?

philip mullins

Posted: Jul 19, 2007 06:57 PM

i think he is saying that he wants to spray from inside the room and then install sheetrock. if i were tryin to do that i believe i would buy some luan or cheap particle board just to be safe. but, you could prob get away with a heavy duty tarp and good staples. just depends on how much $ ur tryin to save. what i dont get is if you can get in there to install tyveck, why cant you get in there to spray?

John Kalinich

Posted: Jul 19, 2007 08:23 PM

OK found a better picture, see link.

My original goal was to find a material to spray the foam against that would "breath" but I guess the foam is actually a vapor barrier making this much less important. My next thought was that the insulation would become self supporting once hardened.

Spraying kneewall onto back of sheetrock from behind is possible, but, cramped quarters would make for a less than happy installer.

Since I am hearing that there is not really a good solution with a "film" material I'm guessing the cost of luan, PB or even plasterboard may be what it takes to do the job right.

A couple new things... There is a small section of transition between knee wall and cieling where I think there should be venting between the roof and insulation to allow flow from behind knee wall to attic. Had thought about using the fiberglass panels made for this in these areas. Then spray foam on them.

Finally a solid material might be the best protection against the occasional mouse or two that visit (this is vacation cabin that is not occupied all the time).

Thanks for all your help!

Tim O'Keefe

Posted: Jul 19, 2007 09:33 PM

Unless this is an extremely steep pitched roof, a 9' kneewall should allow more than sufficient room for an installer to spray foam from behind onto drywall or other finished wall material.

Tim
Granite State Spray Foam Co.

John Shockney

Posted: Jul 19, 2007 10:32 PM

After looking at your picture I would recomend spraying the under side of the roof and use the closed (conditioned) attic system.

thanks
Airpro

Thomas Kasper

Posted: Jul 19, 2007 11:16 PM

I wouldn't spray the knee wall. I'd spray the roof deck. IF possible I'd spray down on the ceiling after the drywall if installed.

Gerry Wagoner

Posted: Jul 20, 2007 04:22 PM

You can install luan board, or cardboard or insulweb fabric and spray to any one of those. Done it many times...

Best wishes,

olger

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