Ceiling insulation question?
Question:I am converting a screened porch to an all season room and the ceiling is sloped from the back of the room to the front. There is lots of room for insulation because the finished ceiling at the back of the room will be about 15 inches below the plywood from the roof. Is it necessary to provide ventilation above the insulation, and if so how can I ventilate as it is a flat roof sloped down from back to front?
Answers:
Ventilation is advisable. You can install rooftop ventilators, which are plastic doodads with holes covered by plastic covers, available at building supply stores.
There is a styrofoam product called "More-vent" ( I think that's the spelling) that allows the air, appx 3 inches deep, to travel between the insulation and roof ply. It comes in 24" width that can be halved.
Done.
You need to try and keep air flow under your roofing, or the extra heat will damage the roof material if it is composition roofing.
Use a R-11 which is only 3.5" thick at the narrow end, and as you get further back use R-19 5.5", etc... Also you can get cardboard baffles from the lumber yard for at the bird block vents between the rafters.
Another option is using a rigid insulation, but it will cost a bit more. No matter what you do, you are going to lose heat in the winter, and gain it in the summer, especially if there are lots of windows.
If it was mine I would just put R-11 threw-out without venting it and call it good enough.
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