Wall science for Hot Humid Climates

Diagram from National institute of Building Sciences - click on illustration to read more

Diagram from National institute of Building Sciences - click on illustration to read more

We love the Emerald Coast and the rest of NW Florida - but we are also live in a hot humid climate zone that is very different then climate zones to the North. Building science has demonstrated that walls need to be built differently then one would think coming from colder climates. In hot-humid regions, walls must be able to dry to the inside. Homeowners in such regions must be educated not to limit the ability of walls to dry toward the interior by adding non-breathable interior finishes on exterior walls. Finishes that could compromise the wall’s ability to dry inward include vinyl wallpaper finishes and vapor diffusion-retarder paints. (see illustration on the right)

In hot-humid climates, exterior wall systems should dry toward the interior by installing vapor retarding materials on the outside of the wall assembly and using vapor-permeable interior materials.

Providing some resistance to outdoor moisture vapor from diffusing into the wall assembly limits moisture problems during hot and humid periods of the year. And by keeping the interior-side of the wall assembly vapor-permeable, any moisture within the wall system can migrate to the cool and dry interior of the building.

If a vapor-retarding material, such as polyethylene or even vinyl wallpaper, is used toward the inside of the wall assembly, it could block vapor migration on its cool surface and cause condensation problems. Instead, materials toward the interior of the wall assembly should be semi-permeable or permeable, such as unfaced fiberglass batts with permeable interior paint on the gypsum board.