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howard.wheaton 05-24-2010 01:58 AM

Soffit
 
I had the aluminum soffit installed over my wood for appearance but more for additional venting. The contractor had a drill with a circular bit and just when down the length of the house every 6" or so and drilled another hole. The aluminum has 10" preforated sections every 36" for airflow? Is that an issue how they did it?

Just Bill 05-24-2010 06:55 AM

There is a gap between the old soffit and the new facia, but the holes and vented pieces should be in the same place, for best efficiency.

howard.wheaton 05-24-2010 01:41 PM

How about if there is soffit along one side of the attic. All the skecthes I have seen for ventilation, shows aire entering on both sides and then leaves out the top of the roof. If air is only coming in from one side, will it circulate enough or just come in one side and out the top?

Gary in WA 05-24-2010 02:43 PM

1.What size holes did he drill?

2.As Bill said, does the new soffit touch the old with the holes?

3.Or is there a 1/2" gap between them?

4. Is there an exhaust vent- continuous ridge or turtle-backs?

Be safe, Gary

howard.wheaton 05-24-2010 04:44 PM

I looked in the attic...

1) There are (3)-1" holes every 46" or so and a a piece of the vented aluminum placed over it. The alumimin vent is rated at 13 sq inches/LF.

2) there are only holes at the vented aluminum.

3) the soffit is about a 1/2 or so away from the aluminum.

4) There are 2 vents on the roof that are 9" circles with nothing mechanical about the,. Look like an upside round pan on the outside.

I only have soffiits on one side of the house and based on the calculations, I have 18.8 sq inches of vented soffits based on the 3 circles at 8 locations. Yikes, right? The attic is 714 sq ft.

Gary in WA 05-25-2010 12:22 AM

1. 13 sq.in. rated but only (3) 1" holes = 2 sq.in. at 8 locations = 16sq.in. need 155sq.in. more.

4. 9" circle = about 50-60sq.in. X 2 = 120 sq.in. need 223sq.in. more. (2 more)

Pi(r2) = 1/2 (radius)= .5x.5= .25x3.1416= .78x3= 2.35 Your (3) 1 holes have a square inch opening of a little more than 2. If they are spaced at 4, they should be at 9sq.in.per ft.x 4= 36sq.in. (you have 2/4= .5sq.in. (1/2) Which should be every foot, not every 4.And would require (3) 3-1/2" holes every foot.


Your 714sq.ft. attic divided by 150= 4.76 sq.ft. with soffit vents and exhaust vents= 4.76 divided by 2= 2.38 2.38 of soffits both sides, divided by for one side= 1.19sq.ft. convert to inches---- 1.19x144= 171.36sq,in.per soffit side. If a vapor barrier in the attic, need 1/2 of totals.


http://www.airvent.com/homeowner/pro...it-specs.shtml


http://www.buildingscience.com/docum...on?full_view=1


Be safe, Gary

howard.wheaton 05-25-2010 01:44 PM

Thanks GBR. The problem is that only one side of the house has soffits, the other side is the rest of the house and the front and back is the peak portion. So if I open up the entire one side of the soffit and make it all the vents, I am looking at 34' of vented soffit and with the 6.5 sq in/LF in free air space for the vent (rated for 13 sq in/LF and soffit is only 6"), I am looking at 221 sq in. So I am short 121 sq in. But since my intake will be more than the exhaust (127 sq in) is that still sufficient? Is it normal to cut open all the soffit on one side of the house to vent? Another thing I noticed also is that in the attic, you can see on one exhaust vent, but you have to look behind plywood that is attached to the rafters to see the other vent. It dosent go all the way from the joist to the ceiling so not why it;s like that. Since the soffit is only on one side of teh house, will the properly vent the the attic?

Tom Struble 05-25-2010 09:43 PM

howard are you having issues that you think may be related to ventilation?sweating ,mold.ice dams?anything like that?

Gary in WA 05-25-2010 10:00 PM

The rating of the soffit material is IF it is completely open on the other side of the grilles. It is not with only (3) 1" holes every 4'. You have .5 sq.in. of vent per foot now. But in reality, you are not venting every lineal foot as you need to (with 9 sq.in. per foot). So rafter bays are not getting the air supply to move the heat away to prevent ice dams/mildew-rot, if applicable.

Uncover the pot vent and add 2 more. Add more screened soffit and add rectangular cutouts above new soffit vents to balance the system.

Where are you located?

Be safe, Gary

howard.wheaton 05-25-2010 10:35 PM

The only issue I am having is the familiy room that the attic is under is 7 degrees hotter in summer and colder in the winter then the rest of the house. The insulation is fine and then when I saw the light coming in at the soffit and started to research. It is best if I just take the 32' of soffit and cut rectangles between all the joists and place vents the entire way. That will give me 208 sq in of air flow or I can just cut out the 8 sections where is have vents and that would make it 52 sq in of air flow.

I live in Chicago.

Tom Struble 05-25-2010 10:51 PM

not saying that you don't need more venting,but its not going to help those issues

howard.wheaton 05-25-2010 11:00 PM

Venting is not going to help cool the house? My research online is showing that I have more output then input, which could create negative pressure and pulling the cool air from the living space. That's not the case?

Tom Struble 05-26-2010 07:24 AM

actually you really don't know what you have as far as venting,your just assuming
typically the soffit area is not very air tight construction to begin with
there are usually gaps between the facia and roof sheathing and between the facia and wood soffit that air can be drawn in thru

like i said you may need more intake and its not a bad idea to provide it
but from what you describe you should be adding more insulation and making sure your attic is airseald from the conditioned space


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