Attic ventilation
posmer
| Posted in General Questions on
Many people where I live have installed solar roof fans to help with their existing roof ridge vents…is this OK, can this cause problems for the roof or shingles ?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Paul,
Powered attic ventilators won't cause any problems for roofs or shingles (unless the flashing was installed incorrectly and the hole in your roof leads to roof leaks).
However, powered attic ventilators can pull indoor air through ceiling cracks, increasing your energy bills and in some cases causing water heaters to backdraft. For more information on this issue, see Fans in the Attic: Do They Help or Do They Hurt?
One more point: the usefulness of attic ventilation is often exaggerated. For more information in this issue, see All About Attic Venting.
Most solar powered attic fans don't pull hard enough to create backdrafting or high infiltration issues. A one-off in-situ test done by the Florida Solar Energy Center showed modest cooling power use reductions (mid-single-digit percentages) can be achieved with the small self-powered units. See:
http://www.fsec.ucf.edu/en/publications/html/FSEC-GP-171-00/
How useful it is to YOUR house will vary, but it's nowhere near as likely to cause problems as higher volume attic ventilators powered off the grid, or wind-driven turbine vents.
I'm no expert on the subject, but to provide a bit of anecdotal evidence, we had an issue with our first floor smelling like the chimney. Had the chimney cleaned but the smell would not go away. After getting a tip from someone, we quit running our two powerful attic fans and the smell completely disappeared. So I tend to agree with Martin's caution that the fans could possibly pull out indoor air from the home and cause exterior air to be pulled into the home at unwanted spots. Having said that, the issue could probably be managed if the fans are sized properly and the soffit vents in the attic ledge are robust enough to permit sufficient airflow to pulled from the outside of the home.