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-   -   Soffit holes, need to line up? (http://www.diychatroom.com/f9/soffit-holes-need-line-up-80856/)

turbomangt 09-08-2010 02:27 PM

Soffit holes, need to line up?
 
How important is it if have the aluminum sofit air vent holes line up with the new cut outs the roofer make in sofit prior to installing the aluminum vent covers? will the air flow up through ridge if all the vents don't line up exactly?

jackofmany 09-08-2010 02:44 PM

I'm picturing your problem and I did this type of work for years. The answer is that yes air will flow but certainly not as efficiently as it would were things lined up as you wish. I missed the area you're in - but would it be impractical to use a greater number of vented soffit panels or a different ratio of solid to vented - thereby achieving more "lined-up" vents?

turbomangt 09-08-2010 03:00 PM

Jack, I'm in chicago, I was wondering if anyone would make sense out of my question. I had my whole exterior done, roof and ridge vent, gutters, hardy baord and aluminum sofits, what they did was cut a bunch of holes with the saw in the sofits, then when it came time for install of the aluminum they just used perferated aluminum vents every four feet or so, well these may or may not line up with exsisting cut outs in wood, that became a concern when my attic temp got up to 130 degrees on 90 degree days. My next task is to go in the attic when its cooler and make sure all insulation is aways from vents, but I won't be able to tell if the cut outs and vents line up, also, I have about 15 feet of a dormer which as you know due to roof line, it has no sofit venting, I wonder if that is a problem and how to handle.

Gary in WA 09-08-2010 05:05 PM

They should line up. Otherwise the exhaust vents on top will pull the easiest air it can, possibly the conditioned air from the house. Your perf's are probably only 4.68sq.in. per ft.You need with 24" deep soffits and 3--4" perf's every 24"--- that's 3 perf's+3 solids, on down the line.

If 12" deep soffit, all perf's to get the required 9 NFVA per ft. 3-- perf's every 4' is way undersized unless you have a vapor barrier on the ceiling/attic (then 1/2 my figures). http://files.buildsite.com/dbderived...rived92755.pdf

http://www.airvent.com/homeowner/pro...it-specs.shtml Check the manufacturer's NFVA on the soffit panels website.

Gary

jackofmany 09-09-2010 07:32 AM

I won't try to complicate things for you at all. If when you can tolerate the attic temp, you notice that insulation (we're talking fiberglass here i assume) is in the way, you can, when it's cooler' place "V" shaped polystyrene baffles - similar to the drop in insulation used behind aluminum siding, between the roof sheathing and the fiberglass. then just restaple the insulation. That allows for free flow of air. If you can - attach a picture or two of this.

Also I know you mentioned ridge vent, but is that the only means of exit for your attic hot air? If so - there are a few other means of getting more airflow. I won't go into anything til I hear what you have. Also - do you - or do you ever plan to have a "whole-house fan?" I used one in Southern PA (where it gets plenty hot at times) and it worked wonders for the old house. There was no central air and it made it comfortable - being able to control your airflow by which windows and or doors you had open.

The dormer you spoke of, I assume it has 2X6 or better rafters. If so - why is that not a ventable area. If its all sealed up and you have insulation in the spaces between the rafters, you're pretty much screwed - unless you want to go to some great lengths to change it. You are right in deducing that ridge vent or any other type of vent isn't worth much if air isn't getting to it.


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