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Circle-D Posted: Mar 28, 2012 07:22 PM	inside or out Hi Mason Have a customer with an unheated sandblasting facility with a metal roof. He is having condensation problems during certain weather conditions. The building is open on both ends with only a curtain type door. To spray foam to the underside of the roof would take considerable cleaning as there is years worth of sandblast grit and dust on the metal roof and truss work. If the foam is sprayed to the outside of the roof would it still work for stopping the condensation issue. This scenario would require a lot less cleaning and probably be more cost efficent. He could keep the building in operation also if it was done on the outside. No downtime and minimal cleaning would offset the cost of the coatings. What thickness would you suggest in either location?
mason Posted: Mar 29, 2012 08:30 AM	Skip, I don't think insulation will help much if the building is open on both ends and the building is not heated. The temperature inside the building (and on the surface of the metal or the foam) would be similar to the outside temperature. Also, the humidity inside the building would be equal to the outside. (unless the operations inside the building are creating higher humidity inside.) However, if the building is heated, then the spray foam could help either installed to the interior or the exterior. You still might have condensation at the curtain doors. So, fans in that area would help circulate the air and prevent condensation. In your area I would suggest 3 inches of closed cell. Remember when spraying exterior applications you need to use a 3 lb density foam covered with an elastomeric coating specifically designed for spray foam roofing. This type of application calls for applicators who are experienced in spray foam roofing. In either case, I would not offer a guarantee that the condensation would be completely stopped.

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Circle-D

Posted: Mar 28, 2012 07:22 PM

inside or out

Hi Mason
Have a customer with an unheated sandblasting facility with a metal roof. He is having condensation problems during certain weather conditions. The building is open on both ends with only a curtain type door.
To spray foam to the underside of the roof would take considerable cleaning as there is years worth of sandblast grit and dust on the metal roof and truss work.
If the foam is sprayed to the outside of the roof would it still work for stopping the condensation issue. This scenario would require a lot less cleaning and probably be more cost efficent. He could keep the building in operation also if it was done on the outside. No downtime and minimal cleaning would offset the cost of the coatings. What thickness would you suggest in either location?

mason

Posted: Mar 29, 2012 08:30 AM

Skip,

I don't think insulation will help much if the building is open on both ends and the building is not heated.

The temperature inside the building (and on the surface of the metal or the foam) would be similar to the outside temperature. Also, the humidity inside the building would be equal to the outside. (unless the operations inside the building are creating higher humidity inside.)

However, if the building is heated, then the spray foam could help either installed to the interior or the exterior. You still might have condensation at the curtain doors. So, fans in that area would help circulate the air and prevent condensation.

In your area I would suggest 3 inches of closed cell. Remember when spraying exterior applications you need to use a 3 lb density foam covered with an elastomeric coating specifically designed for spray foam roofing. This type of application calls for applicators who are experienced in spray foam roofing.

In either case, I would not offer a guarantee that the condensation would be completely stopped.

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