Self-drying roof

"In concept, to qualify as a self-drying roof, the roof assembly must dissipate enough moisture during the drying season to reestablish an acceptable equilibrium moisture content for the materials used, so that at the end of each drying season the materials are not drgraded and the thermal resistance of the insulation is not impaired. Also, there obviously must not be a trend toward long-term accumulation of moisture within the building or roof assembley." --

NRCA, 1996 Some of the design condiseration s an references for design information regarding self-drying roofs, NRCA Roofing and Waterproffing Manual-Fourth Edition, Volume 1, Low-Slope Roofing Text, Section 7.2.3. Rosemont, Ill., National Roofing Contractors Association.

A DESIGN BY R-3

" a membrane, insulation relatively permeable to water vapor, a crack-free wicking layer to disperse any liquid that liaks through cracks in joints of the first insulation layer, insulation relatively impremeable to water vapor, and a vapor permeable deck. If a water-imprmeable vapor retarder is required to prevent upward diffusion of interior moisture into the roof, a self-drying design is NOT possible. A liquid water permeable vapor retarder, which allos liquid water to flow down ward but retards either upward or downward flow of water vapor, could allow a roof to meat the NRCA definition.

Korsgaard, V., Rode, C. and Bunch-Nielsen, T., 1996, The self-drying concept for flat roofs:: "Moisture may enter a roof assembly in a number of different ways. From the interior by diffusion and convection. During construction from moist materials or rain. Later on, rain water may enter through leaks in the roofing."

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