AboutTodd E. Miller Expertise I am available to answer any questions pertaining to residential (or other sloped) metal roofing. I have knowledge of most available products but I like to approach projects from a "needs" basis and analyze them individually. Additionally, I can answer most questions about building ventilation.
Experience I have worked for a manufacturer of residential metal roofing since 1980. I currently serve as President and have been involved with a wide variety of projects of all types across the world.
Organizations I am a board member for Metal Construction Association, Metal Roofing Alliance, the local United Way, our church, and our son's school.
Publications Over the years, I have had articles appear in several trade journals including RSI, Remodeling, and Qualified Remodeler.
Education/Credentials I have a B.A. in Communications and have also completed three years of training with the E-Myth Academy.
Expert: Todd E. Miller Date: 8/1/2008 Subject: attic venting under new metal roof
Question I recently had a metal roof installed over my existing asphalt roof. The new
metal roof is shakes on a batten system (along with a solar thermal system--
a series of looped pipe laid sandwiched between the roofs that collect heat
and ultimately pre-heat my hot water). From what I understand, a titanium
sheet was put over the old asphalt tiles, then the battens with the thermal
system, then the metal shingles. The new roof itself is vented. Previously my
attic was insulated on the floor with blown-in cellulose and then vented.
After the new roof was installed, I went into my attic and realized that the
vents were now covered up. So here are my questions: 1) Is venting the
metal roof alone enough to prevent a moisture buildup problem? It seems to
me that the moisture from the house will still be going up into the attic, so
even if condensation is countered by venting in the metal roof, there's still
moisture getting trapped in the attic, right? Is this an oversight by the
contractor? 2) Or, is there some reason the contractor covered these vents,
and purposely left the attic unvented, in order to help the house retain heat
in winter? (When I go up there, it's hot, but nothing like it used to be.) 3) I'm
considering putting in a whole house fan, which would require me to put in
gable vents (2 sq feet each side) in the attic--is there any harm in having the
roof doubly vented--i.e. both the the metal roof and then the attic as well?
or would this cause some problem? Overall, I'm very pleased with the new
roof and system--the house is definitely cooler, and I hope it will be warmer
in winter. I'd very much like to install the whole house fan, but I don't want to
minimize the energy efficiency of the system I've already installed. I've been
asking my contractor this question, but I'm not sure he understands what I
keep asking. Thanks.
Answer In my opionion you do need attic ventilaton in your situation in order to avoid an unhealthy build-up of moisture. That moisture will collect someplace where it hits dewpoint and then it will condensate. This could happen in an area where it is not visible and the damage could be significant by the time you discover it.
