# venting and insulating ceiling with rigid foam



## Nealtw (Jun 22, 2017)

That is about as good a plan as you can have, Are you in the attic or are you removing ceiling joists? You really do need those soffit vents. What's the plan for bathroom fan?


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## pmp (Feb 6, 2019)

Thanks for the speedy reply, Nealtw!

So fastening drywall to the rafters THROUGH a sheet of rigid foam is a normal thing to do? You just use drywall screws to crew through the drywall and rigid foam into the rafters? 
_____

To answer your questions:



Nealtw said:


> Are you in the attic or are you removing ceiling joists?


I have removed the ceiling joists inside this dormer so that I can raise the ceiling. The ceiling will follow the roof slope. Currently, the rafters are exposed. 



Nealtw said:


> What's the plan for bathroom fan?


I was thinking: 
The bathroom fan will be in a top corner of the room ("top" as in the highest point of the sloped ceiling inside the washroom). A rigid metal duct will exhaust bathroom air out. 

But I am not sure where the duct should exit. 

I've read that exhausting through the soffit is, at least in theory, not good because then you risk sucking moist air up through the soffit vents. But others say this is overly cautious, reasoning that bathroom air is not as moist as a dryer. 

If I don't go out the soffit, then I would go out the side of the dormer. Now, I forgot to mention, for clarity, that my dormer is *a "shed" style dormer, like this* (that's just an image for reference--not my actual house!). If I go out "the side of the dormer" then I mean going out the wall that's the triangular portion of the dormer that's parallel to the house's gable (I don't know what you call it... the gable wall of the dormer? In the reference image, it's the blue triangular piece of wall of the dormer). This may be easier than going out the soffit, but I do like the fact that a soffit vent faces downward, so there's minimal possibility of water leakage--whereas going out the side horizontal wall, rain water would be a problem.

*What's your opinion on where I should vent?*


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## Nealtw (Jun 22, 2017)

Venting into the soffit is definitely a bad idea. The gable of the dormer would work. 
I would sooner see a flat ceiling area at the top so you had a bit of a common attic with the fan up there with the vent out the roof, that way you could wrap insulation around the fan housing. But sealing lights and fans and switches is important to keep moisture from the room from getting into walls and ceiling.


They make 3" drywall screws for that.


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## pmp (Feb 6, 2019)

If I went out the gable of the dormer, would it be good to have the duct slope down as it exits, so that any condensation, or god forbid rainwater, slides away? Any reason not to? 

Thanks again for your help!


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## Nealtw (Jun 22, 2017)

something like this


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## Nealtw (Jun 22, 2017)

This is venting to the soffit


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