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Selecting a Ridge Vent


Yukon Youngun's Avatar
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02-26-11, 03:51 PM   #1  
Selecting a Ridge Vent

Is there an obvious choice among ridge vents? I am about ready to start a large venting/insulating project and the main objective is to add a ridge vent above a bonus room. This wing of the house has a peak about 50' long with only a small gable vent on the windward end and the common perforated soffit vents, nothing else. The area above the bonus room is completely closed. The plan is to add the ridge vent and baffles in each of the rafter spaces above the knee walls.

The ridge runs directly east/west with wind primarily westerly. I'm figuring to use one with external baffles, but I wonder how much impact wind direction has on performance against wind driven rain. Not interested in causing a problem by solving one.

 
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02-26-11, 04:35 PM   #2  
Hi Yukon, I have very little experience with selecting and installing ridge vents, but I have frequently seen water and snow finding their way in. Light powdery snow can follow almost any path, even those gable vents, so difficult to find a perfect solution. We will see what the contractors have to say.

As for your insulation and baffles, air seal before you insulate, the list of places to attend to is long. In addition to the baffles you are thinking of, add wind blocks to keep the incoming air off of the end of the insulation. Good insulation and good air sealing reduces the amount of venting you need.

Bud

 
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02-26-11, 08:39 PM   #3  
If adding the ridge vent block the gable vent.( If not the ridge vent is a waste) Add those foam soffit vent baffles all the way to the ridge vent and insulate.

Mike NJ

 
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02-27-11, 12:12 AM   #4  
Posted By: lawrosa If adding the ridge vent block the gable vent.( If not the ridge vent is a waste) Add those foam soffit vent baffles all the way to the ridge vent and insulate.

Mike NJ
With only one gable vent, I would wait to test and see if both gable and ridge are venting air out from the soffits. If both are working then leave the gable. If replacement air is being pulled in the gable vent, then block it. As for running the baffles all the way to the ridge in a full open attic, I have never seen where that was necessary or beneficial. Mike, please explain.

Bud

 
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02-27-11, 12:21 PM   #5  
The majority of the overall project is all about air sealing. I plan to dig through a lot of blown-in fg in the next few weeks over the whole house. However, the bonus room I mentioned is used for home schooling and is quite uncomfortable in warmer weather and I want to get it resolved before it gets here.

If this works, I am attaching an aerial photo of the house. The continuous peak running more or less horizontal near the bottom is where I am looking to put the ridge vent, and the bonus room occupies about 2/3 the length from the right hand end, to just past the lonely vent from the water heater. The remaining 1/3 of that space is all open attic and has the gable vent. There are soffit vent panels pretty much everywhere they should be.

Blocking the gable vent would not be an issue, but I think the larger question would have to be whether there would be similar interference coming with or from the regular roof vents nearby on the perpendicular section of the house.

Planning to do Provent panels in each rafter space with wind blocks on both sides of the bonus room, then again from the tops of the knee walls to above the collar beams. Should I consider wind blocks at the upper baffles also?

I discovered last night that they actually put additional insulation on top, but it is compressed by some odd stapling and wiring and will have to be helped out a bit. I am particularly concerned about whether I am trading for a new problem with wind driven rain here.

Mike, did you mean literally the baffles to the ridge and insulate all the way up, or merely the baffles just to get past the ceiling? I figured just having the venting in place would go a long way, but I suppose a little more insulation can't hurt. I was also considering radiant barrier in there, especially on the south side.

[IMG]C:\Documents and Settings\user\Desktop\roof layout[/IMG]

 
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02-27-11, 02:22 PM   #6  
Sorry about the size, but here is the photo...

Pictures by Yukon_Youngun - Photobucket

 
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03-02-11, 05:49 PM   #7  
I'm about to do the same thing, but not quite as long a ridge as yours. I've done a 20' section over MBR, and it helped somewhat. IMO, the thing to do is add radiant barrier foil....I did it myself and what a difference in comfort level.
>> The more heat you keep out, the less you have to remove--that is key.
Adding more insulation above that large room will also help. When you do ridge vent, make sure your add sufficient soffit venting. I used Lamanco w/baffles. You can get cobra at Lowes, or shinglevent II. Any of these will work fine, just use 3" nails.

 
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03-04-11, 05:53 AM   #8  
Let me try to condense this project down to more specific questions.
1) Is there an obvious better choice among ridge vents? From what I have read it seems the rigid, baffled panels provide best NFVA and rain ingress protection, so that is what I am planning. A little more effort to install, but apparently I do that alot...
2) Does "imbalance" between upper and lower venting actually cause problems, or is it just about getting enough flow overall? I finally measured out the volume of the attic space -- calculates out to 16 ft. of ridge vent. But I want to cover at least the length of the room to minimize heat transfer in from the roof. That would be 29 ft. No convenient way to estimate what the flow is from the existing perforated soffit vents. What if I just go the whole 48ft?
3) Can I use radiant barrier in lieu of or in conjunction with the rafter baffles? It would be a major pain, but could install the r.b. in each rafter space in the sloped part of the room ceiling to provide both functions.
4) Apply r.b. to outside of knee walls as well?
Thanks, all.

 
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