Insulating vaulted ceiling without soffit vents
NCPack
| Posted in Energy Efficiency and Durability on
I have an unfinished room off my master bedroom i want to finish by insulating against roof rafters for half the ceiling. The apex of the roof will be left without insulation as the vaulted ceiling will terminate into a 6′ flat ceiling due to existing cross braces. Question is, due to the roof over this room being a gable roof, only 3 of the 10 rafter bays terminate to a vented soffit. The entire length of the roof has a ridge vent. I know i am supposed to vent from soffit to ridge vent in the 3 bays, but should i use rafter vents if they do not terminate into a vented soffit?
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Replies
How is it that a gable roof has only 3 of 10 rafter bays ending at a soffit? Is it a dormer ending in a roof valley?
For clarity, when you say the apex will be left without insulation, do you mean without the SAME TYPE as on the inclines, and that it will be covered with cellulose or something? Not insulating the apex would seem a big mistake and likely a much bigger deal than your venting issue...
First you would want to insulate the entire roof and also make sure the ceiling plane is extremely airtight. Then you can worry about the venting. Which, honestly I'm not sure exactly how to best vent rafter bays that terminate in a valley. Perhaps someone else will. You could consider an 'un-vented' approach in its entirety. (Search how to insulate cathedral ceiling here on GBA).
Hi Rob -
In order to ensure we are on the same page, I think you need to provide either photos or a drawing; just too easy to assume something pivotal.
Peter
Pic of exterior roof
Pics of rafters ending in valley, not a vented soffit
Vented bays and flat ceiling at top.
Rob,
When dealing with these types of roofs, what I have done is convert the required code vent area to number of 1" holes per rafter bay (in my case it was 3). Drill the valley rafter. Looks like there is a knee wall space behind there, those are problematic for air leaks, they might cause more problems if interior air from there gets into your insulated rafter space.
I have the same issue and was looking for answers too. If anyone has any answers besides drilling holes into structure to allow airflow from soffit to ridge vent, it would be appreciated. I was thinking you could spray closed cell insulation instead of using all batt insulation.
Rob,
What as the solution to your problem? I am dealing with the same thing currently and can not find a definite answer.