Soffit vents continuous vs. every 3 ft.?

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Old 10-19-06, 10:08 AM
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Soffit vents continuous vs. every 3 ft.?

This question was asked in another thread but not completely answered.

If I install the round individual soffit vents every 3 ft than won't the bays that do not have vents be unventilated?

I would prefer the continuous soffit venting but I beleive I would not be able to do that myself. I could cut disk holes and install the round ones which would mean I would not have to take the facia and soffit boards, and the gutters down.

I have some calls out to roofers but it's hard to get one to come for a small job. Meanwhile winter is coming and I would like to have it done before the first frost.

If I do it myself and put the round soffit vents in, I would want to ventilate every bay. However this would look a little ridiculous. But we have had quite a condensation problem and we have to remedy it soon.

Could someone could explain to me whether every other bay is as good as continuous or not? (perhaps creating a cold roof to prevent the condensation?)

Thanks!!!
 
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Old 10-19-06, 10:25 AM
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I'm far from being an expert on ventilation but I think it is mostly about having enough sq in's of intake and exhaust for the conditions [providing they are sensibly placed]
 
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Old 10-19-06, 10:44 AM
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Wink

There are a lot of ways to go for a vent in the over hang. There are lot of rectangles kind in lots of size's also a 3 " one that come in a strip like. You do want to make sure the air gets up over the insulation in the attic.
You need 1 sq ft of vent for every 150 sq ft of attic. 1/2 in and 1/2 out at the top. For a vent fan. Attic sq ft X 0.7=== CFM of the fan

ED
 
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Old 10-19-06, 09:16 PM
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Attic ventilation involves more than just cutting holes in your soffits. It also includes the way the attic and top plate are insulated. Changing attic venting is best done by someone who can analyze the construction of your home as a whole and can see what needs to be done/modified in order for it to work.

If this is an older house and you currently have a few soffit vents, it is likely that the top plate in that area was left uninsulated to allow air to flow into the attic from that particular area. It could be that the rest of the rafter bays (above the top plate) are plugged with insulation, because that's the way they did it back then. Just cutting more vents (or having continuous vents) in the soffit would not be enough in that situation.

Not sure what its like in your attic, but going up in the attic and examining your air flow is something for you to consider. If you have a condensation problem, the BEST thing you could do is add more insulation. Unless you have already tackled the warm moist air (is there a vapor barrier?) creating a cold roof may only serve to create a lot of frost on the underside of the deck. More ventilation is not necessarily a good thing, since often what happens is that the additional ventilation only serves to draw more energy, heat and moisture out of the home. It's something to think about.
 
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Old 10-20-06, 09:29 AM
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soffit vs continuous cont.

Currently we have no soffit venting. We have a 20yr old cape with vaulted ceilings upstairs and a crawl space with a knee wall. Your right, the knee wall is not insulated and I can't tell if there is insulation under the plywood floor. That will be the next thing for us to do.

We have small removable doors to get in and out and recently we put better magnets on so the doors stay closed better and plumb. We have a ridge vent. We had a new roof put on last year because our first thought was that it was a leak and the roof was 20 yrs old. The the sheet rock on the knee wall was wet when the condensation froze and then melted, but mostly on the end bays where the ridge vent ended. The roofer came back and shortened the ridge vent thinking there was leaking coming down from there, a mistake. The problem got worse. Last week I got him to come back and lengthen the ridge vent to almost the end of the house, thinking there was no ventilation up the last bay or two. I now do have a builder coming next week to put a continuous soffit vent in on both sides. We have had so many "experts" look at it and they can't even agree whether we already have soffits ir not. I can't see any daylight anywhere when I crawl in there with the lights out during the day.

Everything I have read says a ridge vent is useless without an intake vent. Why would they make a house without soffits? Even 20 yrs ago? I would hate to think that our adding soffits will make the condensation worse.
 
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Old 10-20-06, 10:00 PM
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Provided you have a way to get in there and install styrofoam proper vents, and can insulate beneath them, I'd say that a continuous soffit intake would be better at giving you an even flow of cold air.

IMO, a vapor barrier under cathedral ceilings is a must.
 
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