I need some thoughts on a ridge vent. We recently had our roof reroofed (stripped and redone). The contractor suggested we have a “low profile” ridge vent put in across the entire roof – since it is a 1.5 story bungelow with almost no ventilation, he thought it would alleviate how very warm the second floor gets in the summer. There are front and back dormers on the house. The roofers put the ridge vent on both sides of the dormer, but did NOT put it across the ridge where the dormers meet. They thought that the slope of the dormers was not angled enough and that water could leak into the attic via the ridge vent. The contractor says that the ridge vent on both of the dormer should be adequate for ventilation. How can we tell if this is right? If we do need more of a ridge vent, is there an alternative style to use when the roof does not have a steep slope?
Joe Boston, MA
Replies
Is the ridge vent you have balaced with an equal area of soffit vents? If not the ridge is not doing as much for you as is should be. What is the length of the ridge vents you have compared to the total length of the roof? What is the pitch of the roof where the dormers are?
Al Mollitor, Sharon MA
MojoMan,
I have installed round soffit vents (3") in the soffit (actually in the spacer boards between the rafters - the rafters hang over the house about a foot - so there is no 'soffit' per se). The ridge vent was the last part of the ventilation for the house. The attic area is probably 30' long by 15' wide. It is really just a crawl space above the 2nd floor. The regular part of the roof is quite steep - the dormers are not steep at all, although water does drain off of the dormer. The contractor is going to measure the attic area (which should have been done before hand!).
Joe
Generally, if a ridge vent runs 80% or so of the length of the average gable-end house roof, that's more than sufficient. You'll have trouble getting the equivalent amount of ventillation in the eaves, so there's no need for more along the ridge.
The bigger question would be whether the roof over the dormers is effectively vented. If the dormer ceiling isn't "cathedral" style and the area above the ceiling is open to the rest of the non-conditioned attic area, then the ridge area ventillation should be sufficient without vents there. The main issue, again, would be the eave venting.