Bill Rose's article on roof ventilation ("Roof Ventilation Update," 10/07) was an excellent review of the factors that influence vapor accumulation in vented and unvented attics. At the APA/Engineered Wood Association, we have been testing, certifying, and studying the properties of OSB for over 25 years, so we do not share the concern that "we still know too little about the moisture performance of this material."

We know the structural, dimensional, and physical limitations of the product and provide installation guidance to ensure proper performance. We also know that, similar to other untreated wood products, OSB is subject to biological degradation absent proper design, installation, and maintenance of the structure.

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