Does a tile roof in Florida require a ridge vent?
I live in a 4 unit, 2-story condo with Altusa tile over 90lb hot mop underlayment with hip roof design. Each attic is approximately 25′ x 40′, with what appears to be Corning blown insulation. Ducts from the second floor air handler run throughout the attic. 24″ wide soffit ventilation run around the entire building.
A roofer recently told us it is critical we had to install a 6′ off-ridge vent to each unit as soon as possible. Without the ventilation, the attic can overheat causing increased energy bills and possible damage to the decking or underlayment. During severe storms, the roof will flex popping nails from the decking and lead to leaks in the roof. I have also read where quite a few people removed/blocked their vents from tile rooves after we had 3 hurricanes in one year because of significant water damage from water blowing in the vents.
Are the off-ridge vents going to save us a lot of money and extend the life of the roof or are they a waste of money?
Thanks a lot,
Dale
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Replies
A Florida Solar Energy Center study of the attic temperature effects of various roofing types showed that even a fully-vented red tile roof (1:300 vent ratio) will get almost 25° hotter than ambient temperature in the summer. I hate to think what an unvented tile roof will do to the "cool" air in the AC ducts.
While studies have shown that roof color (and solar reflectivity and IR emissivity) is more important than venting for controlling attic temperatures and consequent ceiling heat flux, venting definitely makes a measurable difference.
The question is: do you want to design your roof for the occasional wetting from hurricanes or for daily livability and energy conservation? A vented roof should be able to recover from occasional wetting, while an unvented roof (and yours is unvented without high exit vents) will be a daily problem.
Dale,
Your question is unclear. Is the "Corning blown insulation" installed behind netting between the rafters, creating a cathedralized attic? Or is the "Corning blown insulation" on the attic floor?
If the insulation is on the attic floor, your venting question is irrelevant. Your real problem is the HVAC equipment and ductwork installed outside the home's thermal envelope.
Hi Martin, yes the insulation is on the floor of the attic. The duct work runs mostly on top of the insulation in the attic. So you are saying save money on the off-ridge vent and spend it on better duct work in the attic?
Thanks,
Dale
Dale,
HVAC equipment and ductwork in an unconditioned attic is a disaster. Who cares if the attic is ventilated?
If you are going to invest any money at all, I would seal all vents and insulate the roof plane to create a cathedralized attic. But that would be expensive. Too bad your designer put the HVAC equipment and ductwork outside of your home's thermal envelope.