Q. I have to re-roof, and I’m being told to put a vent in the top of my roof instead of an attic vent fan that sticks up. They described it like a slit under the top shingles that is more hidden than the fan cover sticking up above the roof. What do you think of their idea? Is it just as good or better?
A. Many years ago I made the mistake of following the latest fad in roofing. Ridge venting was touted as a great way to vent the roof, since heat rises and the vent is located under the top shingles. What the roofer does is cut the wood sheathing at the peak to leave a 2-inch-or-so-wide gap that air can escape from. Next they place a specially made honeycomb-like filter over the gap and then nail the shingles to it.
The problem with this method is that it doesn’t allow for enough air movement. Your roof and attic get choked with heat buildup, the shingles heat up like strips of bacon on a frying pan and little by little they become brittle in the middle. Sounds like a song, but you won’t be singing when you see the pieces of shingles come rolling off your roof. If you have any doubt about what I’m saying, you only have to see my backyard after any windstorm and to count the flakes of roofing coming off while I try to settle with my insurance company from the “superstorm.”
The insurance company will probably give you a hard time about how your shingles weren’t installed correctly, without telling you why they think that. The installation of the shingles has to follow manufacturer’s requirements, which include proper venting of your roof. Whoever told you that the little strip of venting at the top of your roof would somehow be enough hasn’t yet learned the hard way what heat buildup can do.
The latest version of the building codes actually has formulas for calculating the minimum venting requirements for various conditions. Just like most of the regulations in the building codes, the information given is for the minimum requirement only, and, generally speaking, should be used as a baseline to be exceeded using safety factors to cover extreme conditions. Venting is important. Keeping the roof structure below the shingles cool enough to avoid harming the shingles is critical to their performance.
An alternative method gaining popularity is to condition and insulate the attic to be cooler. It makes sense to do this, especially since most air conditioning fan units are located in hot spaces, making them work even harder to circulate cool air throughout your home, and costing you more. So save your money by putting in the through-the-roof vent fans. Solar-operated fan units, costing more, save much more in the long run.
©2013 Monte Leeper. Readers are encouraged to send questions to firstname.lastname@example.org, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.