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Dennis Myers Posted: Apr 06, 2012 04:27 PM	Spraying Open Cell into enclosed rafter bay. We get a lot of jobs on cape style homes. Most have rooms built into the 2nd floor with a 4ft kneewall, 3-4 foot "cathedral" slope, then flat ceiling for 4-6 foot depending upon the home. I have never tried spraying open cell into an enclosed space, so I am wondering if I could pull the 1" of paper insulation out of the cathedral slope section of the ceiling and spray open cell into it. If I blocked off the top of each bay, and sprayed it in from the bottom would that bow out the sheet rock? Ideally I would like to fill the rafter bays from the soffit to the top of sloped section of the wall, then just blow in cellulose up on top, or even if enough space is there do a complete hot roof.
Jeremiah Hein Posted: Apr 06, 2012 05:50 PM	You can lower the temps and pressures to slow the foam reaction time and make it easier but it will more than likely still bow and crack the sheetrock in a few places, ask me how I know.... Demilec has both an open and closed cell pour in place foam designed for this application. The only thing you need is a tip for the end of the gun that you attach some plastic hose onto. I suppose it depends on what gun your using we've got the Fusion AP. I've not tried the closed cell but we do quite a bit of work with open cell it's a little bit more expensive and you almost always end up with half a drum sitting around for a while. But it makes doing these jobs possible. We also use it for block fill and injecting it into uninsulated walls. And unlike phelonic foams this product doesn't shrink or put a lot of moisture in enclosed areas. There's a lot of trial and error but it works pretty well once you get going.

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Comments

Dennis Myers

Posted: Apr 06, 2012 04:27 PM

Spraying Open Cell into enclosed rafter bay.

We get a lot of jobs on cape style homes. Most have rooms built into the 2nd floor with a 4ft kneewall, 3-4 foot "cathedral" slope, then flat ceiling for 4-6 foot depending upon the home.

I have never tried spraying open cell into an enclosed space, so I am wondering if I could pull the 1" of paper insulation out of the cathedral slope section of the ceiling and spray open cell into it. If I blocked off the top of each bay, and sprayed it in from the bottom would that bow out the sheet rock?

Ideally I would like to fill the rafter bays from the soffit to the top of sloped section of the wall, then just blow in cellulose up on top, or even if enough space is there do a complete hot roof.

Jeremiah Hein

Posted: Apr 06, 2012 05:50 PM

You can lower the temps and pressures to slow the foam reaction time and make it easier but it will more than likely still bow and crack the sheetrock in a few places, ask me how I know....

Demilec has both an open and closed cell pour in place foam designed for this application. The only thing you need is a tip for the end of the gun that you attach some plastic hose onto. I suppose it depends on what gun your using we've got the Fusion AP.

I've not tried the closed cell but we do quite a bit of work with open cell it's a little bit more expensive and you almost always end up with half a drum sitting around for a while. But it makes doing these jobs possible. We also use it for block fill and injecting it into uninsulated walls. And unlike phelonic foams this product doesn't shrink or put a lot of moisture in enclosed areas.

There's a lot of trial and error but it works pretty well once you get going.

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