Expert: Michael J. Owen - 11/5/2009

Question
just built home now 2yrs old, no venting was installed due to interior ceilings not completed.now completed how do I vent to prevent condensation? they installed 1" insulation on top of perlins then metal roof.1" insul has a R30 value this wraps the whole house. do I use gable venting, ridge venting or both? no soffit venting was used but can be installed.
 thanks

Answer
Hi David. I prefer and usually recommend ridge venting with soffit vents. The rule of thumb is one square foot of vent for every 150 sq/ft of attic space. Gable vents do work to a point but the hot air has to be pushed or pulled towards them. Ridge vents are so much better because they are at the highest point and distributed across the entire roof. Here is a web site that should help you:

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

Hope this answers you question.