Enough venting in flat roof attics?

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Old 06-09-03, 12:12 AM
Tired hands
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Enough venting in flat roof attics?

My house is about 30 yrs old, with mansard roofs (alot of flat roof area) with 3 attics. There are vents covered with mesh screen material under all the eves and one or two has exhaust fans- on the top of the roof-which presently isn't working. And I believe the roofer told me he closed off one of the roof vents (exhaust fans) due to a potential problem with water leaking in. I am in the process of moving back some blown in insulation away from the eve vents. My questions are: How do I know if there is enough air circulation in the attics? And, what temperture is normal/desired for the attic? Will the upstairs be cooler if I have more exhaust fans? Don't be too technical--I'm a housewife that does all the maintenance and repairs because hubby doesn't.
 
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Old 06-09-03, 08:32 AM
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Mansard roofs are usualy a problem when it comes to venting. There are basically 2 parts of this type of roof. One is the flat portion and the other is the steep portion or sides if you prefer. Your eave vents can either be at the top or bottom of the steep portion of the roof. In most cases the eave vents are located at the bottom of the steep portion. I need to know where your eave vents are located before I can give my opinion. You can tell if the eave vents are located at the top portion of the steep roof by looking at the shingles in that area. If the shingles drape over the steep portion from the flat portion of the roof, then the eave vents are at the bottom of the steep roof. If the shingles stop on the flat portion and there is a small gap between the flat and steep sections of the roof, then the eave vents are on the top of the steep portion of the roof.
 
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Old 06-09-03, 09:10 AM
Tired hands
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Mansard vents

Thank you for your quick reply. The venting is at the lower portion under the eaves below the shingles and gutters. The venting is about an 1 1/2 inches wide and run most of the length of the eaves with only about 8 inches of solid areas inbetween the vents. The venting is covered with metal screen. I've been in the attic and there's not any moisture or rotting or dark wood.

Our bedrooms are upstairs and it does get warm in the summer here in Arkansas. I've added insulation, which has helped. The exhaust fans are controlled by switch not thermostat. I was told to turn them on in summer off in winter. The roofer thought there was enough circulation with only the venting in the eaves, but then not sure if he knows. I've also wondered if there was a paint (white) that I could use on the flat part of the roof to reflect the heat. Winters are mild and not a problem. What is an appropriate temperature in the attic in summer? Thanks again for your help.
 
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Old 06-09-03, 01:07 PM
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http://www.eere.energy.gov/EE/buildings_envelope.html
This is a Dept. of Energy site on energy efficient building and it discusses "Cool Roofing." Most paints applied for this purpose is either silver or aluminum colored. Believe or not it does extend the life of the roof too, besides making the house cooler. If you search the web for "Reflective roofing paints" you will find quite a few to choose from.

http://www.naima.org/pages/resources...tml/BI458.HTML
This site has some nice illustrations for you to see concerening ventilation and it gives you the rule of thumb for adequate ventilation. It explains that there should be clear air passage from the eave vents to the roof vents on the flat portion. If insulation is obstructing the air flow, then you do not have free venting. Assuming you have adequate free venting, it means that 50% of the venting should be eaves and 50% should be roof vents. So if your roof needed 3 sq. ft. of free venting, then you need 1.5 sq. ft. of eave vents and 1.5 sq. ft. of roof vents.

One attic 1850 cfm attic fan and the reflective roofing paint coupled with adequate free venting should drop the temperature of the house dramatically.

If there is anything you find difficult to understand, please feel free to ask.
 
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