avoid the problems of excess moisture it is necessary to limit or control the amount of water vapor in the house. This can be ac- complished by modifying lifestyle activities and/or by using mechanical means such as exhaust fans, dehumidifiers. To reduce moisture vapor production within the hou- se the following can be implemented. • Decrease shower time. • Maintain heat at 68Â° F and not hi- gher. • Avoid boiling water or liquids excessi- vely. • Limiting clothes washing to full loads. • Do not dry clothes inside the home. • Opening windows a bit to allow mois- ture to escape and promote air move- ment. • Install properly sized dehumidifier(s) Ice Dams In cold climates, the effects of ice dams are sometimes mistaken for condensation problems. Snow can melt over the heated portion of the attic and run down to the roof overhang where it re-freezes. This ice can build up to form a trough to catch water right over the wall. The water then backs under the shingles and runs down through the wall or ceiling, causing stains on the inside face of the wall or ceiling, or paint peeling from siding. Good ceiling insula- tion and attic ventilation at the eaves keep the roof at temperatures near outdoor air temperature and thus prevent melting until warmer weather. Another good preventive in areas where ice dams are prevalent, is the use of a wide roll roofing under the shingles parallel to the eave and exten- ding over the wall. Then, if ice dams do occur, water cannot get through the roof. Crawl Spaces Moisture from crawl spaces may eventually enter the living space and raise the humi- dity, or it may move directly into wall cavi- ties. The major source of moisture is the soil. An effective solution is the installation
of a soil cover using a vapor-retardant ma- terial, which is tear and puncture resistant. The material is simply laid on the soil with all joints lapped and held in place at the ed- ges by gravel, bricks or other weights. Roll roofing has been used for many years, but more recently, 6-mil polyethylene has be- come more popular. The effectiveness of soil covers is recognized by major codes and standards, which allow reduction of ventilation to one-tenth that required where no soil cover is used. The usual ventilation requirement without a soil cover is one sq. ft. per 150 sq. ft. of soil area, with vents distributed for cross ventilation to all areas. This normally means a minimum of four openings with one near each corner. Whe- re a soil cover is used, the ventilation can be reduced to one sq. ft. per 1500 sq. ft. of soil area, but good cross ventilation is still required. Drainage away from the building is always critical, since water standing on top of the soil cover negates any advan- tage. In problem areas, a sump drain is a good precaution. Slab On-Grade Foundations Where houses are built on concrete slabs, a moisture barrier should be placed under the slab to prevent soil moisture from ri- sing into the house. The material should be tear and puncture resistant such as a heavy polyethylene. Good drainage away from the house is especially important.
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