Indoor Air Quality

Recently there has been a lot of press given to indoor air quality in new homes. Specifically, mold has been the hot subject. Mold spores are present in the air in most parts of the country most of the year. Mold can grow on almost any surface. The main cause of Mold growth is excessive moisture. “There is no practical way to eliminate mold and mold spores from the indoor environment; the way to control indoor mold growth is to control moisture”, quoted from the United States Environmental Protection Agency, Mold Resources web site http://www.epa.gov/iaq/pubs/moldresources.html. This web site has extensive explanation on the cause, clean up and prevention of mold growth. Below, we have provided a fact sheet with information on what AvisAmerica does to help prevent mold growth and promote indoor air quality. We have also attached a sheet of recommendations for builders to consider in the site installation of our homes.

In order to control the growth of mold, we need to address four areas; prevention of moisture, prevention of unconditioned air entering the home, (air infiltration), control of indoor sources of moisture, and ventilation of attic and crawl spaces.

Prevention of water infiltration

Flashing is used around windows and doors to move moisture to the exterior.
Butyl caulking is used around doors so water seal is maintained after final door adjustments.
Exclusive use of kiln-dried lumber and indoor assembly means our homes are not subject to rain during the manufacturing process.

Prevention of air infiltration

Wall sheathing is glued to studs, top and bottom plates. This acts like a gasket as well as glue.
Sheathing also overlaps wall plate to floor and plate to ceiling perimeter, covering the gap as seen in typical site construction where the sheathing has a gap at the top and bottom of the wall.
Window flanges caulked to sheathing and flashing.
Draft stop used on all wall top and bottom plate penetrations where electric wires and pipes penetrate the assembly.
Recessed light fixtures are air tight and rated for insulation contact.
Draft stop caulk used on electrical devices penetrating the drywall. Specifically, around recessed light fixtures.
Gaskets installed on underside of receptacle and switch covers. (optional)
Air infiltration barrier installed behind siding. (optional)

Control of moisture at the source, mechanical ventilation

Bath fans are ducted to exterior.
Bath fan duct is insulated to prevent condensation inside the duct.
Clothes dryer is vented to the exterior. Duct installation may be on site.
Range hood is ducted to exterior. (optional where conditions permit).
Continuous duty bath fan with timer. (optional)

Ventilation of attic space

Continuous vented soffits installed at eave overhang.
Ridge vent is site installed to promote air ventilation from eave to the ridge and to the exterior.
Baffles are installed to maintain a clear air path through insulation where required.

Recommendations for the builder on site

Apply caulk or construction adhesive to all “belly band” joints before applying sheathing.
On attic and basement mating gaps use expanding urethane spray foam in set gaps to control air infiltration.
Be sure a good connection is made to all roof and wall boots for fan and dryer vents. Install the duct as short and direct as possible. Do not leave sags or extra duct in attic to prevent water from collecting in duct.
Insulate basement walls instead of basement ceiling.
Ventilate crawl spaces and use poly or other vapor barrier under the slab to prevent moisture from coming up through the slab.
Ventilate basement when pouring concrete floor, or apply plastic sheeting to underside of module floor while concrete cures. This will prevent moisture from entering module floor during the first few hours of concrete curing.
If any materials get wet during the set or finish process, be sure it is dried well or replaced before it develops mold. This is especially important with fiberglass insulation and carpet.
Install footing drains on perimeter of foundation to eliminate moisture from entering the basement.
Use an energy recovery ventilator on HVAC systems to automatically introduce fresh conditioned air into the home.