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Reverse Vapor Drive?? Post New Topic | Post Reply
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Luke Kujacznski
Posted: Apr 17, 2007 12:01 PM
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Reverse Vapor Drive??
I have a job where we are insulating a tank that is going to be cooled. Spraying 3in of roofing foam 2.5 pound and then were planning on covering with acrylic topcoat. But I just talked to someone who warned me about a reverse vapor drive, i.e. the tank is cold in summer thus drawing heat twards it, if the coating is not vapor proof will the foam become water logged? Any help is appreciated.Luke |
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Posted: Apr 17, 2007 08:00 PM
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ah... luke skywalker,,,, with 2.5" closed cell you have a vapor permience well below 1.0... thus 1 of the "beni's" of closed cell foam... this vessel could be heated or chilled with no adverse effects due to moisture vapor drive... but be sure you have enough Uvalue to meet the thermal requirements of the chilled vessel... ps...think primer... |
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Gerry Wagoner
Posted: Apr 18, 2007 05:45 PM
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Hi Luke. It depends on how cold the fluid is to be kept. Get this number. Generally speaking, the rigid foam should resist vapor intrusion, unless it is a cold storage, or freezer. Acrylics have minimal vapor barrier properties, although the thicker they are applied the lower the perm. If there is any question, use a urethane coating, or run the project through WUFI to determine the hydrostatic pressure (if any). olger |
