Re: Open cell between rafters - to do or not to do?
rey ---- a couple of thoughts.
Insulating the underside of the roof ( hot roof ) shouldn't be an issue with moisture.
You have to think of the reasoning for venting the attic in the first place. A long time ago there was little consideration in preventing warm moist air entering this space. Instead it was discovered a long time ago that warm moist air was entering this space and condensing. The long time remedy was to allow lots of venting to try and remove the moisture rather than preventing it into this space in the first place.
A long time ago I learned that venting is over rated.
The principal behind insulating the attic is turning this into a semi conditioned space.
I will point out that it's insulating all the exterior surfaces of the attic and not just the underside of the roof. The reason is to minimize heat gain during summer months reducing the cooling load for A/C.
Durning the winter this would reduce the heat loss and reduce the heating load for the furnace.
The other benefit is keeping the temperature above the dew point of the moisture and preventing condensation during the winter.
This is not dissimilar to insualting a wall.
"" an ounce of perception -- a pound of obscure "