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-   -   Circular Screened Soffit Vents (http://www.diychatroom.com/f9/circular-screened-soffit-vents-111356/)

Erky 07-20-2011 12:45 AM

Circular Screened Soffit Vents
 
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Writing from Omaha Nebraska. Sons living in a house --- a 1950/s era stone ranch with simple hip roof --- and no soffit vents. There are two vents on the roof to the south side - that's it.

With recent heat and humidity the attic is venting excessive heat into the closet where the attic access is located, and there is condensation on the walls in that bedroom.

Am thinking we need to retro fit with soffit vents - the roof profile is so low that we can't reach the soffit area from the access. We're looking at installing 4 " circular screened soffit vents from the exterior.

Input?

Grumpy 07-20-2011 08:14 AM

Was there a question? Sounds like a good plan, just ensure you install enough vents to compensate for the fact that there is nearly zero exhaust. Have you considered installation of additional exhaust? It may help too.

Assuming your house is 1,000 sq ft, you would want no less than 3 exhaust vent (144 NFA each) and 18 16"x4" soffit vents. I don't know the NFA on the 4" round but I would assume/guesstimate you would need 72 4" circular round vents. now if your house is NOT 1,000 sq ft, you can extrapolate a pretty close idea to what ventilation you need based on the numbers above.

Without intake, to meet minimum code and shingle warranty requirements, you would need 7 roof vents on a 1,000 sq ft house.

Also insulate that ceiling hatch, there are a number of products that can help you out but a simple piece of pink foam board insulation from home cheapo will certainly aid in the heat loss you are experiencing.

AGWhitehouse 07-20-2011 11:12 AM

You can place venting at the ridge line which can be installed from the exterior.

-- Static vents are cheap and have no moving parts. These are essentially the same a bathroom exhaust fan vent caps.

-- Powered ventilators require and electrical feed but can come equipment with thermostats and humistats that activate the fan when either level goes above your preset setting.

-- Turbine Vents are passive fans that utilize outside winds and/or breezes to drive a exhaust fan system. This is a slight improvement over the static vent type system.

Grumpy 07-20-2011 12:12 PM

Ridge vent is usually not a good choice on hip roofs as there is seldom ever enough ridge on a hip roof. Using my 1,000 sq ft example the roof would require 27 linear feet of ridge vent. The intake would be the same.

Actually intake would NOT be the same. While a mushroom/canned/turtle vent would work without an intake it works better with an intake. Ridge vent will not work without intake period, it needs intake. So no, intake would not be the same you would NEED 18 16"x4" vents. Youwould also want to remvoe the existing mushroom vents, do not mix.

Fans are a good choice also on hip roofs, you could intall a fan in place of one mushroom vent and cover over the other vent. You would also want to create intake or the fan motor would burn out. However you would then want to increase to 28 16"x4" intake vents. Don't forget to factor electrical usage, or consider a solar fan. Solar fans are not quite as powerful as traditional hard wired electric fans.


more info can be found at www.airvent.com www.rollvent.com

AGWhitehouse 07-20-2011 12:19 PM

Sorry for the confusion, my suggestion on fans/vents at the hip was totally dependent on the addition of intake at the soffits which Grumpy covered beautifully.

I agree the standard ridge vent is useless in a hip application. The passive "vents" I described were meant to be mushroom/canned/turtle type.


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