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Matt Kenner Posted: Sep 25, 2009 04:00 PM	spray foam to concrete Anyone know what kind of yield losses I can expect when spraying 2lb foam to the ceiling of a parking deck?
Posted: Sep 29, 2009 05:27 AM	pends on ambient temp,, if below 50 use 25% so you dont take a beating,,,
richard sucher II Posted: Sep 29, 2009 03:06 PM	what yield number are you using for your base. What yield less 25% at 50 degrees? 4200 - 4500 - 5000 board feet. Where do you start to figure the loss? Thanks.
Matt Kenner Posted: Sep 29, 2009 03:09 PM	the normal yield for the 2lb spray foam I use is around 4500 board feet. So, 25% yeild loss would be around 1125 board feet or I would get approx. 3400 board feet per set of closed cell.
richard sucher II Posted: Sep 29, 2009 03:43 PM	have been watching this subject very close lately as colder weather is upon us. Have asked various suppliers for their base number and 4200-4500 appears to be the consensus for ideal conditions at 80 degrees for two pound closed cell foam. I have also seen a chart that calculates loss of yields for different temps and for 50 degrees the loss is listed at 10%. Chart lists around 27 degrees for 25 per cent loss. Good luck -with 4200 as base with 15% loss - approximately 3600 board feet looks like doable number for yield at 50 degrees. Conservative on yield base and high on potential loss of yield percentage.
Harry S Posted: Sep 30, 2009 09:54 AM	Wouldn't the % of yield be less than 25% if the crete was sealed real good?
Dennis Davidson Posted: Oct 01, 2009 08:21 AM	It doesn't matter if the concrete is sealed or not, nor does it matter what the ambient temp is. It's all about the substrate surface temp.. I've sprayed exterior walls while the ambient was near freezing, but the surface was warmer. Your biggest problem is going to be getting the foam to react before it drips on to the floor. As far as loss of yield goes, you can expect about 25% but that will only apply to the first ( min.1") layer of foam. After that there will be very little yield loss. Also, beware of "foam shear" spraying on a cold surface.
Matt Kenner Posted: Oct 01, 2009 08:50 AM	Can you explain "foam shear"?
Matt Kenner Posted: Oct 01, 2009 12:11 PM	Also, does anybody know whether code requires a thermal barrier be applied to the spray foam if the ceiling (which is concrete) is also the floor for condominiums? Is the concrete enough to be a barrier or does it need thermal barrier?
Dennis Davidson Posted: Oct 01, 2009 04:40 PM	"Foam shear" is when a large area of fresh foam pulls itself from the surface. Usually caused by the foam not reacting properly on a cold surface. It doesn't react because the cold substrate absorbs all the heat out of the foam restricting the reaction. This is known as "heat Sink". It creates a higher density foam at the substrate surface (about 1/4" thick) which doesn't have the flexibility like the rest of the foam on top of it does. As the foam cools, it shrinks just enough to pull itself off the surface creating "foam shear". It doesn't matter what the substrate is, it's all about the surface temperature. As far as needing a thermal barrier on a concrete parking garage. Best to check with local building code. I think you would need one because the foam would be considered a "contributor" in the event of a fire creating a hazard in the "occupied space" of the parking garage area. But, it's been about 20 years since I've sprayed a parking garage and the rules have changed.
Posted: Oct 01, 2009 06:59 PM

Author

Comments

Matt Kenner

Posted: Sep 25, 2009 04:00 PM

spray foam to concrete

Anyone know what kind of yield losses I can expect when spraying 2lb foam to the ceiling of a parking deck?

Posted: Sep 29, 2009 05:27 AM

pends on ambient temp,,
if below 50 use 25% so you dont take a beating,,,

richard sucher II

Posted: Sep 29, 2009 03:06 PM

what yield number are you using for your base. What yield less 25% at 50 degrees? 4200 - 4500 - 5000 board feet. Where do you start to figure the loss? Thanks.

Matt Kenner

Posted: Sep 29, 2009 03:09 PM

the normal yield for the 2lb spray foam I use is around 4500 board feet. So, 25% yeild loss would be around 1125 board feet or I would get approx. 3400 board feet per set of closed cell.

richard sucher II

Posted: Sep 29, 2009 03:43 PM

have been watching this subject very close lately as colder weather is upon us. Have asked various suppliers for their base number and 4200-4500 appears to be the consensus for ideal conditions at 80 degrees for two pound closed cell foam. I have also seen a chart that calculates loss of yields for different temps and for 50 degrees the loss is listed at 10%. Chart lists around 27 degrees for 25 per cent loss.

Good luck -with 4200 as base with 15% loss - approximately 3600 board feet looks like doable number for yield at 50 degrees. Conservative on yield base and high on potential loss of yield percentage.

Harry S

Posted: Sep 30, 2009 09:54 AM

Wouldn't the % of yield be less than 25% if the crete was sealed real good?

Dennis Davidson

Posted: Oct 01, 2009 08:21 AM

It doesn't matter if the concrete is sealed or not, nor does it matter what the ambient temp is. It's all about the substrate surface temp.. I've sprayed exterior walls while the ambient was near freezing, but the surface was warmer. Your biggest problem is going to be getting the foam to react before it drips on to the floor.
As far as loss of yield goes, you can expect about 25% but that will only apply to the first ( min.1") layer of foam. After that there will be very little yield loss. Also, beware of "foam shear" spraying on a cold surface.

Matt Kenner

Posted: Oct 01, 2009 08:50 AM

Can you explain "foam shear"?

Matt Kenner

Posted: Oct 01, 2009 12:11 PM

Also, does anybody know whether code requires a thermal barrier be applied to the spray foam if the ceiling (which is concrete) is also the floor for condominiums? Is the concrete enough to be a barrier or does it need thermal barrier?

Dennis Davidson

Posted: Oct 01, 2009 04:40 PM

"Foam shear" is when a large area of fresh foam pulls itself from the surface. Usually caused by the foam not reacting properly on a cold surface. It doesn't react because the cold substrate absorbs all the heat out of the foam restricting the reaction. This is known as "heat Sink". It creates a higher density foam at the substrate surface (about 1/4" thick) which doesn't have the flexibility like the rest of the foam on top of it does. As the foam cools, it shrinks just enough to pull itself off the surface creating "foam shear". It doesn't matter what the substrate is, it's all about the surface temperature.
As far as needing a thermal barrier on a concrete parking garage. Best to check with local building code. I think you would need one because the foam would be considered a "contributor" in the event of a fire creating a hazard in the "occupied space" of the parking garage area. But, it's been about 20 years since I've sprayed a parking garage and the rules have changed.

Posted: Oct 01, 2009 06:59 PM

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