home » tech-talk » vapor barriers in florida

Vapor Barriers in Florida

Foam insulation removes the need to trap moisture.

In the first article comparing the northern and southern climates, we talked about the similarities in building design despite the differences in climate. This was never more obvious than in the placement of a vapor barrier.

Up north, it is necessary to place some kind of vapor seal like plastic, or some other non-pervious barrier on the inside of the living area to stop the outflow of humidity. This humidity is necessary for indoor comfort. But in Florida, we have all the humidity we need, or want, and then some. We shouldn't trap moisture to keep it in, we should try to keep it out. So where is the logical place to put it? Inside the wall or outside?

Actually, the answer is neither.

Our climate is so humid that if it were placed on either side of the wall, it would trap moisture within the wall cavities. Our walls need to have both sides available for moisture removal. But an air infiltration retarder (AIR) can be placed inside the wall itself, slowing down the flow of water vapor from the outside. This makes it easier for our A/C system to condense and remove it.

Our Core-Fill 500 masonry insulation qualifies as air infiltration retarder that slows down the passage of air and humidity through the wall assembly, screening out allergens, mold, mildew, etc.