roof vent question
hip roof – cathedral ceiling – stick built – south Florida – 100% a/c. – tile roofing
down at the lumber yard and was talking to the estimators about how people were venting the above mentioned roofs.
seems there were 2 basic ways:
1/ soffit vent going to the corrugated material on the underside of the sheathing above the insulation. underlayment your choice.
2/ then they mentioned some are going with a totally sealed bay. soffit vent to sealed blocking to insulated bay. ice and water shield as underlayment
does anyone know exactly what the performance difference between the 2 would be.
Slightly more insulation means could be a bit cheaper to cool or heat normally but since you would primarily be cooling, I think the vent would help
No vents makes it a hot roof and in S FL the shingles might be aged out a year or so earlier than a vented roof
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Hipped, huh? If it's a pointy-top, or one with relatively short ridgelines, where's all that hot moist air going to escape? Waitaminute.
Woops! Hemmed in by my regional practices, I'm thinking ridge vent.
I recall on my last driving tour through Dixie, seeing a whole lotta those can-vent thingies, dotted all over roofs, up near the tops. Really standing out when you're on a freeway, and seeing the rears of subdivision homes.
I missed the hip style - focused on cathedral. To be honest, I don't think I've ever seen a hipped cathedral roof and cieling. That must be some unique engineering! Since it would be hard to vent, I might be inclined to make it a hot roof then - with urethene foam
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the O.P. says tile roof---so probably doesn't need to worry about cooking the shingles---------and as we both suspect--that may be a marginal issue anyway.
however--if shingles WERE going to be used in this application, i would contact the shingle manufacturer BEFORE the house was built if at all possible.
At one time I prepared a roof proposal for an existing house with similar issues--and ELK was willing to warranty the roof materials if certain conditions were met. in the O.P. situation--it would be nice to know what those conditions are, BEFORE installation. LOL
Best wishes, Stephen
actually i did a little more research and came upon some studies done by the florida solar eneregy board. seems the best way is spray insulation. this causes a sealed cell and no moisture intrusion. seems venting allows in moisture and this is not a good thing. seems the color of the tile/shingles/etc. is the basic variable for roof temp. black is bad...white is good