I’ve heard that using spray foam underneath roof decking will shorten the life of the shingles and void the roof’s warranty. Is this true?

Years ago, when spray foam was first being used, some roofing companies feared that the increased heat deflection caused by spray foam would speed up the deterioration of roofing shingles. Upon further testing and inspection, however, these fears were found to be, well, unfounded. Although this myth still exists, you’ll be happy to know that spray foam will not void your roof’s warranty. As for the shortened lifespan of the shingles, there is some validity to it! A 30-year shingle might be shortened to a 29-year-and-8-month shingle. (In other words, you have nothing to worry about.)