1.2lb open cell foam | Ask Mason Knowles - SPF Consultant | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

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andy buff Posted: Sep 11, 2007 08:31 PM	1.2lb open cell foam If i'm using 1.2lb foam puting in 4-5 inches in the walls 6-7 inches to the roof deck do Istill need a vapor retarder?or because of the amount of inches the vapor transmission perms3.55 @3.5 inches. compared to .5 lb foam thatas 10.55@3.5 inches.I have read some of mark bombergs and your articals saying i need to have a vapor retarder with open cell foam?I live near syracuse.thanks
Gerry Wagoner Posted: Sep 11, 2007 09:36 PM	The manufacturer states that 5.5" and more negates the need for a vapor barrier. Hope that helps. (My guys are spraying 1.2 today).
andy buff Posted: Sep 11, 2007 09:55 PM	Olger,how do you like the 1.2 hows the yeild?have you used any 1 lb? thanks
mason Posted: Sep 12, 2007 09:39 AM	1.2 lb density foam has a higher perm rating than your nominal 2 lb density foam but lower than the .5 lb density foam. I would have a hygrothermal modeling study performed on the specific type of application in your climate area to verify the thickness required and whether an additional vapor retarder is required. All the studies I have seen and the anecdotal history I am familiar with are based on either the 2 lb sprayfoam or the .5 lb sprayfoam. The 1.2 lb density is a relatively new product on the market with different physical properties than the traditional low density and medium density sprayfoams. So, I would do my homework and verify the manufacturer's recommendation. Ask for references, check them out and do the modeling to see if condensation would be a problem.
andy buff Posted: Sep 12, 2007 04:06 PM	Mason,how does one have a hygrothermal model study done??and if one uses .5lb foam whats the best barrier to use poly or paint?....thanks
Gerry Wagoner Posted: Sep 12, 2007 09:53 PM	`lo Skinny. My main sprayer is an artist - in other words he likes his work to look pretty (and it does). That often means more skins buried in the foam, which means less yield. At a YMCA project last fall, we realized 8320 ft2 per set. Not bad. Last month - only 6240 (1.2). My "artist" had numerous lifts in the foam. Spray 3" in one pass and it yields great. The one pound yields about 9000-10000 bf. Haven't had any troubles with APEX. One thing, it doesn't get along too well with VFI 730 as you use 730 to flush the 1.2. Wasted about 100 strokes on a MH (no less). Looked like a deformed queen mattress, the waste did. Funny how some foams interact kindly and others do not. NAP foam gets along pretty well with APEX (line flushing). VFI & APEX need counseling. Still good stuff. Best wishes, oG
mason Posted: Sep 13, 2007 06:27 AM	You can do the calculations yourself by downloading the SPFA document AY 118 Moisture Vapor Transmission at sprayfoam.org. Or ask your supplier if they can do the work for you. Any HVAC company can do the calculations also.

Author

Comments

andy buff

Posted: Sep 11, 2007 08:31 PM

1.2lb open cell foam

If i'm using 1.2lb foam puting in 4-5 inches in the walls 6-7 inches to the roof deck do Istill need a vapor retarder?or because of the amount of inches the vapor transmission perms3.55 @3.5 inches. compared to .5 lb foam thatas 10.55@3.5 inches.I have read some of mark bombergs and your articals saying i need to have a vapor retarder with open cell foam?I live near syracuse.thanks

Gerry Wagoner

Posted: Sep 11, 2007 09:36 PM

The manufacturer states that 5.5" and more negates the need for a vapor barrier. Hope that helps.

(My guys are spraying 1.2 today).

andy buff

Posted: Sep 11, 2007 09:55 PM

Olger,how do you like the 1.2 hows the yeild?have you used any 1 lb? thanks

mason

Posted: Sep 12, 2007 09:39 AM

1.2 lb density foam has a higher perm rating than your nominal 2 lb density foam but lower than the .5 lb density foam. I would have a hygrothermal modeling study performed on the specific type of application in your climate area to verify the thickness required and whether an additional vapor retarder is required.

All the studies I have seen and the anecdotal history I am familiar with are based on either the 2 lb sprayfoam or the .5 lb sprayfoam. The 1.2 lb density is a relatively new product on the market with different physical properties than the traditional low density and medium density sprayfoams. So, I would do my homework and verify the manufacturer's recommendation. Ask for references, check them out and do the modeling to see if condensation would be a problem.

andy buff

Posted: Sep 12, 2007 04:06 PM

Mason,how does one have a hygrothermal model study done??and if one uses .5lb foam whats the best barrier to use poly or paint?....thanks

Gerry Wagoner

Posted: Sep 12, 2007 09:53 PM

`lo Skinny.

My main sprayer is an artist - in other words he likes his work to look pretty (and it does). That often means more skins buried in the foam, which means less yield.

At a YMCA project last fall, we realized 8320 ft2 per set. Not bad. Last month - only 6240 (1.2). My "artist" had numerous lifts in the foam. Spray 3" in one pass and it yields great.

The one pound yields about 9000-10000 bf. Haven't had any troubles with APEX. One thing, it doesn't get along too well with VFI 730 as you use 730 to flush the 1.2. Wasted about 100 strokes on a MH (no less). Looked like a deformed queen mattress, the waste did.

Funny how some foams interact kindly and others do not. NAP foam gets along pretty well with APEX (line flushing). VFI & APEX need counseling.

Still good stuff.

Best wishes,

oG

mason

Posted: Sep 13, 2007 06:27 AM

You can do the calculations yourself by downloading the SPFA document AY 118 Moisture Vapor Transmission at sprayfoam.org. Or ask your supplier if they can do the work for you. Any HVAC company can do the calculations also.

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