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-   -   Soffit Vents (http://www.diychatroom.com/f19/soffit-vents-23165/)

Sammy 07-04-2008 12:22 PM

Soffit Vents
 
Happy Fourth to all!

I have a 1979ish ranch that has had the soffits vinyl sided by a previous owner. The siding used has the obligatory section of vent holes every six feet or so which I am sure do not match up with the actual vents cut in the plyboard on the soffits. I have about nine 6" diameter passive vents and one powered vent fan up at the peak of the roof.

I want to improve the soffit vents to help cool the attic a little more hopefully without replacing all of the siding in place now.

Are there cut in vents designed to work with existing vinyl siding?

If I add more vents while doing this is it possible to have too much ventilation?

Thanks
Sammy

buletbob 07-04-2008 02:06 PM

If it was me I would go and replace the entire soffit. this way to can see if they cut the proper holes for the vent. What I do is remove the plywood soffit from the house and install insulation baffles as i go. then install a perforated panel the entire length of the soffit. There is . In my opinion no such thing as to much venting. as long as you have the proper insulation in the attic.
you will notice that the power fan will work much better pulling the cooler air from the soffits . I would also close up the gable vents if you have any and install a ridge vent once you perform the above.
Good luck BOB

Sammy 07-05-2008 09:34 AM

I think there are sufficient vents cut in the plyboard, they are just covered by the vinyl. Several houses around me are the exact same model without the vinyl so I can compare.

The J track for the siding was put up before the gutters so I was trying to avoid having to take it all down.

I dont have any gable vents and will sure consider the ridge vent when the roof needs redone.

Is there a minimum square footage of ventalation per sqare footage of attic space?

This has been on my list to do for awhile but our electric rates just went up 17 percent here in Va so looking for a few ways to keep the house cooler.

buletbob 07-05-2008 12:35 PM

Gable vents are one solution , best would be to have one at each end to facilitate the flow of air across the attic space. It does not work as well as soffit venting as because its effectiveness is more determined by wind movement. Soffit/ridge venting is more effective because it is determined by convection.

806.2 Minimum area.
The total net free ventilating area shall not be less than 1 to 150 of the area of the space ventilated except that the total area is permitted to be reduced to 1 to 300, provided at least 50 percent and not more than 80 percent of the required ventilating area is provided by ventilators located in the upper portion of the space to be ventilated at least 3 feet (914 mm) above eave or cornice vents with the balance of the required ventilation provided by eave or cornice vents. As an alternative, the net free cross-ventilation area may be reduced to 1 to 300 when a vapor barrier having a transmission rate not exceeding 1 perm (57.4 mg/s m2Pa) is installed on the warm side of the ceiling.

806.3 Vent clearance.
Where eave or cornice vents are installed, insulation shall not block the free flow of air. A minimum of a 1-inch (25.4 mm) space shall be provided between the insulation and the roof sheathing at the location of the vent.

Hows the insulation in the attic.
I use 1sf/100sf of attic space Hope this helps BOB

Sammy 07-05-2008 01:57 PM

The insulation was just overlayed last year and is about an R44 but there is no vapor barrier.

Its 85ish and cloudy here today but I can already hear the vent fan in the attic running which comes on about 110 degrees.

buletbob 07-05-2008 04:56 PM

That's a good R- Value Most likely the first layer of insulation has the vapor barrier. you do not want to have to vapor barriers, what I would ask next is the rafter bays leading into the soffits packed with the insulation. there must be a clear air flow from the soffits to the air fan. or the fan will not have the required exhaust.
anything else feel free to post Bob!

747 07-05-2008 05:46 PM

Quote:

Originally Posted by Sammy (Post 135979)
Happy Fourth to all!

I have a 1979ish ranch that has had the soffits vinyl sided by a previous owner. The siding used has the obligatory section of vent holes every six feet or so which I am sure do not match up with the actual vents cut in the plyboard on the soffits. I have about nine 6" diameter passive vents and one powered vent fan up at the peak of the roof.

I want to improve the soffit vents to help cool the attic a little more hopefully without replacing all of the siding in place now.

Are there cut in vents designed to work with existing vinyl siding?

If I add more vents while doing this is it possible to have too much ventilation?

Thanks
Sammy


I would hire someone to rip out the soffits vinyl and plywood. Rebuild with aluminium. Look in yellow pages for vinyl siding contractor. All those guys would rebuild those no problem. I have intake like every foot on my soffits which are aluminium with the little slits in it.

747 07-05-2008 05:51 PM

The one poster is correct. Add the baffels between roof joist to correspond with the slits in the aluminium. Or as he says a continuous run on the soffits with aluminium thats what i mean. Somebody like him could knock those out in no time. Its not that bad of a job.

747 07-05-2008 05:54 PM

i don't like gable vents. Best is to have the soffits in aluminium with the slits in is continuous no plywood under neath. Then have either a continuous ridge vent or proper louver vents on back side of the ridge spaced out like every 3 feet or so.

1655graff 07-07-2008 07:31 PM

I do not want to hijack the post, but it hits on a question I did not get an answer to when I had to replace the roof. Namely: venting for finished soffits.

1) How does one retrofit finished soffits for better ventilation?

Ours looks to be stucco-coverd plywood. I am concerned that I not drill holes in the plywood that don't lead to anywhere (ventilation-wise).

2) What kind of contractor will do this kind of work (well)?

I had a roofer tell me to go get a carpenter. He told me, "Nope, not my job." No one else I talked to seemed to know.

Because I was persistent, the roofer went ahead an used ridge-line vents where possible on our hip roof (NOTE: The roof has 2 ridges and one 4-sided pyramid). It cut down on the number and placement of the eye-lid vents.

3) We have 2 tips of corners where the plywood soffit is sagging a bit, but no signs of leaks (prior or now) -- NorthEastern and NorthWestern corners. What's the cure and what's causing it? The house was built in 1956.

Thanks.


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