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Corey Degetaire Posted: Oct 20, 2008 09:16 PM	Open Cell around AC penetrations and Ducts? If OC foam is applied the AC Penetrations, flexable duct work, and the air distributor, should there be any concern for condensation and moisture being trapped between the foam and any substrate such as the tin on the duct penetration or the air distributor? I am applying 6" of OC foam above the ceiling directly above the sheet rock, there for the attic will be vented and may experience extremely high temperatures during the hot louisiana summers,which is where her duct work will be sitting, i want to make sure my client gets the max benifit from her foam insulation choice that is why i want encapsulate the ducts. What thickness do you suggest i apply here? I was thinking around 1.5" to 2".
mason Posted: Oct 21, 2008 08:43 AM	Open cell foam has a perm rating of around 10 to 15 per 3.5 inches. This allows a fair amount of moisture vapor to flow through the foam. If it hits a cold surface, condensation will occur. I would use a vapor barrier coating over the foam or use a closed cell foam on the ducts.
Eric Smith Posted: Oct 23, 2008 06:14 PM	Whats the perm rating on CC?
Eric Machemer Posted: Oct 23, 2008 07:05 PM	You should check the manufacturer data sheet, but you can figure generally that 2lb density CC foam at 2" thick would have a perm rating of less than 1.0 At this point, CC foam is an effective vapor retarder. We spray baysystems cc and the most recent data sheet shows a perm rating of 0.80 at 1" thick and 0.23 at a 3 1/2" thickness. Therefore it is a highly effective vapor retarder.
mason Posted: Oct 25, 2008 08:36 AM	As Foamrun reported, ccSPF will average between 2 to 3 perms per inch. At 2-3 inches thick ccSPF would qualify as a vapor retarder according to the 2006 IBC and IRC codes.

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Comments

Corey Degetaire

Posted: Oct 20, 2008 09:16 PM

Open Cell around AC penetrations and Ducts?

If OC foam is applied the AC Penetrations, flexable duct work, and the air distributor, should there be any concern for condensation and moisture being trapped between the foam and any substrate such as the tin on the duct penetration or the air distributor? I am applying 6" of OC foam above the ceiling directly above the sheet rock, there for the attic will be vented and may experience extremely high temperatures during the hot louisiana summers,which is where her duct work will be sitting, i want to make sure my client gets the max benifit from her foam insulation choice that is why i want encapsulate the ducts. What thickness do you suggest i apply here? I was thinking around 1.5" to 2".

mason

Posted: Oct 21, 2008 08:43 AM

Open cell foam has a perm rating of around 10 to 15 per 3.5 inches. This allows a fair amount of moisture vapor to flow through the foam. If it hits a cold surface, condensation will occur.

I would use a vapor barrier coating over the foam or use a closed cell foam on the ducts.

Eric Smith

Posted: Oct 23, 2008 06:14 PM

Whats the perm rating on CC?

Eric Machemer

Posted: Oct 23, 2008 07:05 PM

You should check the manufacturer data sheet, but you can figure generally that 2lb density CC foam at 2" thick would have a perm rating of less than 1.0

At this point, CC foam is an effective vapor retarder.

We spray baysystems cc and the most recent data sheet shows a perm rating of 0.80 at 1" thick and 0.23 at a 3 1/2" thickness. Therefore it is a highly effective vapor retarder.

mason

Posted: Oct 25, 2008 08:36 AM

As Foamrun reported, ccSPF will average between 2 to 3 perms per inch. At 2-3 inches thick ccSPF would qualify as a vapor retarder according to the 2006 IBC and IRC codes.

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