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Roofing Division oWENS Technical Services Bulletin CORNING Application of WeatherLock® Over the Entire Roof Deck Bulletin Number: RD — 10/01/07 DATE: October 10, 2007 WeatherLock Meets ASTM D 1970 FROM: Mel Sancrant — BMTS, Toledo PHONE: (419) 248 -5500 Issue: This Technical Bulletin is to address Owens Corning's position regarding the application of WeatherLock over the entire roof deck underneath asphalt shingles. Key Considerations: • WeatherLock underlayment is a moisture and vapor retarder. Lack of ventilation may result in condensation problems, trapping moisture in the roof deck. • Excessive moisture in the roof deck may result in the following: o Excessive deck movement o Rotting of the deck o Wet insulation • Consult a qualified design professional on moisture control • Check compliance with local building codes Owens Corning's Position: It is acceptable to install WeatherLock or any self - adhered underlayment meeting ASTM D 1970 over the entire roof under Owens Corning shingles, if the following ventilation requirements are met. Attics and rafter spaces must have a total net free vent area of one square feet per 150 square feet of attic floor or ceiling area. The ratio can be reduced to 1/300, if there is a vapor retarder having a transmission rate not exceeding one perm, installed on the warm side of the ceiling OR where a balance system can be achieved. For a balanced system, ventilation should be equal at the undereave and ridge. In cases where a balanced system cannot be achieve, always provide more than 50% of the total required ventilation at the undereave and the remainder at the upper portion of the roof. Proper ventilation is critical when considering covering the entire deck. WeatherLock must be installed according to our application instructions and precautions.