Answer: Unfortunately, I can't answer your question. Owens Corning does not manufacture or market attic fans so I have never done a commercial for the product. My recommendation is to write to the manufacturer (if you already bought an attic fan), or review the information on the packaging in a store (if you have not). The product will probably have instructions inside the package as well. You can also Google the question and see what comes up. When I did that, the search engine came up with 408,000 results.