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Old 06-17-2011, 01:14 PM   #1
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Question about vent placement


Well, the roof is done. I had a Certainteed Integrity roof system installed. On my low roof, I had a Shinglevent II\Edge Vent combo installed. Looks pretty slick! Let's hope it works. On the main roof, the ridge was pretty short so I opted for mushroom vents. The back of my house faces west, so they recommended that I put most of the vents there (plus you can't see them from the street. I also have one on the North side and South side of the high part of the roof. I'm wondering now if this was the correct placement.





The ones on the far left and right are above my bedroom ceilings venting a little area that seems to be like a knee wall (when they cut out the wood for the vent, all they saw was the plaster ceiling. No insulation). The next two are actually on the low part of the attic wall just above my 8" of blow in.

I'm just wondering if I will get optimum ventilation with the placement of those 4 vents or should I of gotten more put on the north and south side. Since there is no insulation in those small sections, I'm guessing those rooms that are below are going to get cold in the winter?

Another question I was if I wanted them removed, is it a roofing no-no to remove the vents, fill in the holes, and roof over where the vents were and relocate them somewhere else now that the new roof is on?



Thanks for reading,

Lew
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Old 06-19-2011, 09:45 PM   #2
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Question about vent placement


Welcome to the forum!

Here are the basics: http://www.airvent.com/homeowner/pro...it-specs.shtml

You may want to measure their size for the NFVA. I would cover the exposed glu-lam beam that shouldn't be exposed to the weather and add blocking between rafters, even if a covered patio......

Gary
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Old 06-19-2011, 10:44 PM   #3
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Question about vent placement


Thanks for the reply Gary!

I appreciate the link. However, I still don't know if the vent placement was correct.

That roof over the porch is loooong gong. It needs to be torn down and rebuilt. Going to leave it as is until I can afford to rebuild it.

Last edited by Sweet Lew; 06-19-2011 at 10:47 PM.
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Old 06-22-2011, 08:21 PM   #4
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Question about vent placement


Figure the attic needs equal exhaust and intakes. At 150 rather than 300 (w.Vapor barrier) the intakes should be in every rafter bay at 9 NFVA per ft., and exhaust double that to cover both sides of the roof (18 NFVA). So an 8x8" turtle-back static vent is around 56 NFVA / 2 = 26 NFVA, or good for: / 9 = 3 lineal feet apart. Your one at the peak is about 5' distance from the other on a straight distance so it is under=sized unless the statics are 10 x10" or other..... hard to tell from a picture, should be stamped on them.
Without insulation, you will have ice dams if the vents are unable to remove the warmed house air rising from the conditioned space below, or at least no snow in those areas. You really need to seal any air leaks in the top plates and drywall/plaster joints of the exterior ceiling/wall. http://bct.nrc.umass.edu/index.php/p...ting-ice-dams/

http://www.familyhandyman.com/DIY-Pr...s/Step-By-Step

http://www.wag-aic.org/1999/WAG_99_baker.pdf

Gary
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Old 06-29-2011, 09:00 AM   #5
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Question about vent placement


Thanks again Gary for the reply. So the next step is to add more insulation. However, that roof has little to no intake (no soffits to add vents). I am working with the roofer to see if they can retrofit some intake from Air-Vent.
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Old 07-01-2011, 10:19 AM   #6
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Question about vent placement


The mushroom vents aren't really doing much if you don't have an intake method within the soffits. The 2009 Internation Building Code states that the intake to an attic space should be 3'-0" lower than the exhaust. This is to assist with natural convection.

If you can't get venting at the soffits, then you could install powered ventilators.
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Old 07-01-2011, 10:29 AM   #7
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Question about vent placement


Thanks for the reply! I'm thinking of having the lower vents removed and leaving the one on the peak unless the roofers agree to retro-fit an Edge Vent on that side. I did a little reading on a power intake and unless I have some sort of soffit vent (which I don't), then I should not use a power intake fan. At least that's what GAF says:

http://www.gaf.com/Roofing/Residenti...e-Booster.aspx#
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Old 07-01-2011, 10:36 AM   #8
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Question about vent placement


You would need some sort of intake source for a powered fan though it would not required to be a soffit vent. For un-powered applications you would need the soffit and ridge to allow the hot air to rise and create a convective current. With a powered fan you will be forcing the exchange of air and, as result, do not require the intake to be lower. You could put in gable end louvers as an example.
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Old 07-01-2011, 10:43 AM   #9
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