Battling Condensation: Determining the Best Method of Control

– By Mark Mullins, Fabral

As suppliers and installers of metal roofing, we have all likely dealt with the issue of condensation. There are several control methods available so the first consideration must be towards looking at the building construction to then determine the best method of controlling condensation. It’s crucial to have conversations with customers and end users about condensation. The condensation control measures can, and most likely will, affect cost, so owners must be in the loop and fully educated as to their options. It’s always best to educate the customer so they can make an informed decision about the next course of action.

This education starts with understanding the source of the issue. Condensation is caused when warm moist air inside a structure comes in contact with the cooler under side of the metal. The metal does not “sweat” – moisture must be introduced from another source, such as cooking or showering in residential projects. In post-frame structure, moisture stems from outdoor humidity, damp ground or animals.

When working with metal, three weapons are traditionally deployed in the battle against condensation: ventilation, insulation and vapor barriers. Venting removes the warmer moist air from the structure but requires open air flow from eave to ridge for this method to work properly. Insulation is used to keep attic space as close to the outside air temperature as possible but is only applicable to heated and cooled structures with an attic, such as a home. Vapor barriers prevent moist air from getting to the back of the metal panels but again are typically used only on projects with a solid deck such as a home.

This of course begs the question of what to do with open framed structures that typically have no attic space to vent or a solid deck to apply a vapor barrier. In this case, insulation blankets can be used between the purlins and the metal roof panels, but there are other alternatives to this available in the market. Condensation control products can be applied to the back of the metal panels during the fabrication process. It is always best to check with the panel manufacturer and inquire about what type of products they offer to help you effectively wage your battle against condensation.

For more information on condensation options e-mail questions to:

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