I’m planning a small addition to my house in coastal South Carolina. I am concerned with the roof venting and the roofs insulation. It will be two stories and the main section will measure 16’x25′. The roof will be a hip roof with two dormers (on the small sides) with louvers for venting. There will be a 36″ deep eve. (on the main roof) with exposed rafter tails. The roof will be 5v metal. The pitch 8 /12. The air handler may need to be in the attic.
1. Will 2×6 for roof rafters be sufficient or 2×8? If 2×8 I would want to taper rafter tails so facia would not be so large, I would not have to with 2×6.
2. What type of insulation? Spray foam? Batts?
3. Do I insulate the roof and the second story ceiling?
4. If using batts should there be a ridge vent?
5. How to get air in (with out a soffit vent) at top between roof rafters? I’ve seen these small round vents that go between the rafters, any other ideas?
6. How do the rafter bays that do not go to ridge breathe? Or is it the whole attic that breaths?
7. Are baffles only used in vaulted ceilings?
8. What keeps insulation from blocking a ridge vent?
Thank you in advance for help with any of these questions.
Replies
There are a hundred variables that all need to work together to do this. these are not separate issues.
What sort of systems is existant on the house you are adding to?
Why the dormers for venting?
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the old house is one story and does not have much venting. the addition and the old house will not share any roof aspects. the dormers were intended partly for looks and partly for venting.
thank you in advance for help.
brad
Ny first thought is that if budget is not a primary concern, then condition the attic space and foam the rafter spaces with Corbond ( Polyurethene spray foam) and no venting. But it is possible to create a cold roof assembly by running furring over the roof sheathing and then the metal roof. Save the dormers for faux pretty.
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