April2017

ATTIC FANS... from page 22.

and most roof shingle manufacturers prohibit the use of attic fans with upper passive ventilation components. As previously noted, attic fans typi- cally do not run in the winter months. Without any upper passive ventilation to allow warm moist air entering the attic from the occupied space below a means to escape. This creates conditions conducive to the formation of condensation on cool surfaces that are in contact with the exterior. Condensation and moisture can lead to the formation of microbial growth, more commonly referred to as mold. Furthermore, without proper ven- tilation in the winter months, the air temperature within the attic space will be significantly higher than the exteri- or air temperature. In the Northeast, this is a primary cause of ice dams. Ice dams occur when the warm air in the attic causes the temperature of the roof to rise above freezing. As the snow on the surface of the roof melts, it travels down the roof until reaching the eave and gutter, where tempera- tures remain below freezing. As the water re-freezes at the eave, it creates an ice dam. As the cycle continues, water traveling down the surface of the roof begins to back up the roof, under the roof shingles where it can infiltrate into the attic space resulting in leaks to the interior. Another issue that has been identified with attic fans is their tendency to pull conditioned air out of the occupied space of the home. In the summer months, drawing cool air from within the home into the attic results in energy

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