PATH - A Public Private Partnership for Advancing Housing Technology

[IMAGE: Tech Set Title]

Moisture Management

Moisture can effect both a home's durability and indoor air quality. 'Wet walls' can lead to mold and even rotting studs. The extensive use of vapor barriers and air sealing can help prevent moisture problems.

Air Sealing

Proper air sealing will lower a home's energy use and increase comfort levels by reducing the amount of air infiltration into a home. Air sealing will also improve a home's durability by minimizing the amount of moisture penetration into the walls and living spaces.

Southface's Air Sealing Checklist

Be sure to seal the platform intersections, such as the joists to sill plate and deck to wall plate, since these are frequently overlooked.

Water Sealing

A vapor retarder, or a vapor barrier, is a layer in the building envelope that restricts the diffusion of water vapor. Water vapor will go from an area of high vapor pressure (i.e., high humidity) to low vapor pressure (i.e., low humidity). Typically, indoor air in cold climates is at a higher vapor pressure than outdoor air, which is dryer and colder. The opposite is true in hot/humid climates, where the lower vapor pressure is indoors (and accentuated by the use of air conditioners and dehumidifiers).

A smart vapor retarder exhibits low permeance under dry conditions and much higher permeance under damp conditions. In cold weather, the product is designed to function much like a conventional vapor retarder, blocking vapor flow from inside the house into the wall cavity. However, during hot weather, a smart vapor retarder will permit a damp wall cavity to dry towards the indoors. It can also be used in mixed-humid climates where conventional vapor retarder placement is problematic. Smart vapor retarders are not recommended for hot-humid climates.

When installing vapor retarders, remember to also install them next to the attic insulation. Most homes are now built with vapor retarders in the exterior walls, but the attic is often neglected. Attics are critical because they often experience high levels of humidity.

For additional information on vapor retarders, visit PATH's Durability by Design.

Content updated on 3/2/2006

 |  |  |  |  |  

Builders Remodelers Manufacturers Design Professionals Affordable Housing Providers Realtors, Appraisers Insurance Industry Financial Services Researchers HOMEOWNERS

Home |  Search PATHnet |  Contact Us |  Privacy Policy

Graphical Version