Attic Ventilation Design Strategies for Manufactured Homes (October 2002, 42 p.)
A literature search and review was conducted to investigate attic ventilation design strategies for manufactured homes. The findings of the literature review were debated among, and analyzed by, a Steering Committee of industry representatives. The literature reveals that ventilation of attic and cathedral ceiling air cavities have been recommended building practices for four reasons: moisture control, energy conservation, asphalt shingle durability, and ice dam prevention. U.S. building codes, including the HUD-code, require attic ventilation in most cases for all climates. The practice of ventilating all attics is based on research conducted in cold climates. Studies in other areas suggest that optimal attic system design may vary significantly by climate.
The research concluded that homes in the hot, humid climate may benefit the most from alternate attic design strategies, including an unvented attic design. A program of testing is proposed to evaluate various attic design strategies including an unvented attic constructed simply by eliminating the ventilation openings, a sealed attic constructed by intentionally sealing the roof cavity, an attic with insulation in the roof plane, and a conventionally constructed vented attic. The end product of this proposed work would be one or more attic designs for hot, humid climates with improved moisture control performance characteristics.