Warm roof
user-6830164| Posted inGBA Pro Helpon
I have a cathedral ceiling , there is insulation in the ceiling joists. There is blocking half way up the ceiling between the joists . There is no vent or space in the ceiling so no airflow as designed . I don’t think the last owner knew that it was a warm roof so he put I n a ridge vent . I am gong to replace the roof , should I take off the ridge vent as well as the soffit vents , or just insure the is a good insulation from one ent to another. Would it help to prevent any moisture going in from the drywall if I was able to find paint to serve as a vapor barrier. that stopped air from going into the roof, if there is a product.
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Replies
Generally, if you have an assembly that works, don't mess with it. A ridge vent is a good thing and can prevent moisture accumulation in climate zones where you can't do an unvented roof with batts.
The bigger problems are usually canned pot lights, those need to go.
OK , Thank You Akos
Reroofing is a good time to consider exterior rigid foam if you want to add some insurance to that unvented roof assembly. That might be something to consider.
Bill
+1 on bringing it up to code. You never know how close to the edge you are and what might trigger future problems.
There is an interesting question about whether such vents are worth having, even without soffit-to-ridge airflow. I expect yes.
I generally go with the approach of not messing things up, but if the assembly is old and significantly under-insulated, bumping it up a bit probably makes more sense. If you're doing this, exterior insulation is the way to go, though it can be a bit complicated if the roof is not a simple plane. Do check the current insulation. If you're adding exterior insulation, you want to make sure there's no airflow above the insulation in the rafters. If there is, the money spent on exterior foam is wasted. With the right thickness of exterior foam, there is no need for interior vapor barrier paint. In fact, allowing some drying to the interior is a good thing.