Expert: Michael J. Owen - 7/3/2009

Question
QUESTION: I live in middle Georgia area and am replacing entire roof on 2 story home with architectural asphalt shingles. Roof pitch: gable 12/12, hip 10/12.  Total attic is 1,650 s.f. and 7,012 c.f. Present venting is 1,350 cfm power vent fan in hip area(980 S.F.) and (3) static vents (each unit approximately 10" sq.) in gable area (670 s.f.). The present venting will remain (replaced if necessary). The roofer plans to add ridge venting , about 23 l.f. in the gable area. The ridge is about 2 ft. above the static vents. Is there a problem with this system? Appreciate your
suggestions and comments.
Thanks , Bob

ANSWER: Hi Bob. I am a great believer in ridge venting as it is the highest point on the roof especially with the steep pitch you have. The rule of thumb is one square foot of venting for every 150 sf of attic area.
Here is a web site that should help you decide the best way to vent your attic.

http://www.rd.com/18231/article18231.html

---------- FOLLOW-UP ----------

QUESTION: Michael, thanks for prompt reply. Will there be a problem using both ridge venting and the satic vents a couple of feet below the ridge venting?  One roofer stated using both may comprise each.  He implied the ridge venting would
draw hot outside air thru the static vents. Again, thanks in advance.

Answer
Hi again Bob. I don't think anything would be compromised as the out side air may be 90 degrees but the air inside the attic space could well be 130 or more. Therefore, in theory, it should exhaust out of either ridge or static vent. If you knew a building consultant or architect, they may be better equipped to help. Sorry I can't be more specific.