Flat roof ventilation

Old 05-08-03, 02:29 PM
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Flat roof ventilation

I'm not sure if this question belongs in this forum.

My house is extremely hot when the temperature is above 75. I have a flat roof and I don't have an attic. I don't think I have any insulation under the roof.

Besides adding central air, what can I do to make the house cooler?

I plan on getting a neoprene roof put on but I was curious about insulation and ventilation. I can't see any signs of ventilation on the front of the house, is there another area where I should look?

Once I tear out the ceilings under the roof, if I put baffles against the roof and then insulation under them (closer to the floor), would this provide sufficient ventilation?

Any other suggestions?
Old 05-08-03, 09:49 PM
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In the vast majority of cases there is an attic with flat roof houses. In your case there is probably no access to it but getting access or creating access to the attic is not that difficult. My advice to you would be get in contact with a local insulating contractor and get an estimate from him for installing insulation and ventilation. Insulating and ventilating a flat roof house will make a dramatic difference in the comfort and energy costs.

The big difference between steep roofing, a 4 in 12 or more pitched roof and a low sloped or flat roof, less than a 4 in 12 pitched roof is that steep roofs are water shedding systems and low sloped roofs are water tight systems. Noeprene (polychloroprene, late 1950's) and Hypalon (clorosulfonated polyethylene, CSPE, mid 1960's) are DuPont brand names. They are part of the synthetic rubber roofing products. Others are chlorinated polyethylene (CPE, 1964), Polyisobutylene (PIB, mid 1970's) and both are compatible with asphalt. One that is not compatible with asphalt but rarely used on residential applications is Ethylene Propylene Diene Monomer (EPDM, early 1970's). All of these are known as single ply products. Neoprene is a name most people know and some contractors use this name for all types of synthetic rubber roofing products. The biggest problem with this product is flashing details. This is because of the thermal expansion and contraction of the product. Though the product may act favorably to the thermal expansion and contraction, where the product seals (water tight not shedding) around roof penetrations is a concern. This really is a workmanship issue. You should be very careful in choosing a contractor.

The reason I am telling you all this is that besides recommending that you choose a light colored roofing product or painting the roof with an aluminum paint to reflect heat from the roof, I am also recommending that you install a turbine fan as part of the attic ventilation system. Reducing the average roof temperature not only will reduce you cooling cost and increase your comfort but it will also prolong the life of the roof. By the way, the primary purpose of attic ventilation is to prolong the life of the roof and the secondary aspect is to reduce cooling costs and increase inside home comfort. The turbine fan will penetrate the roof and you want it installed prior to or when you are having a new roof put on. NOT AFTERWARDS!

It has been my experience that this type of roofing material last longer than the flashing details. Again this is a workmanship issue, especially with water tight systems.
Old 05-09-03, 06:29 AM
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Thanks a lot for your assistance! This was very helpful!

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