Inadequate attic venting intake through soffit


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Old 04-17-22, 02:33 PM
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Inadequate attic venting intake through soffit

I recently replaced my roof and though I inquired about the intake venting, the roofer did not address it. They pointed to my perforated aluminum soffit panels and said “it’s good”. I just check by removing one of the panels and found (6) .5” drilled in the original plywood soffit. There is also what looks like a powdery light dust on the underside of the plywood soffit. What is the best way to increase the ventilation. I have come up with three ideas:
1. remove all the amulinum soffit, sand the original plywood soffit which looks to be in decent condition and paint it. Cut vents in as needed and install grates.

2. pull off all perforated panels and use a 4 or 5” hole saw to cut holes in the plywood then reinstall perforated aluminum soffit panels.

3. go to every other joist bay and drill a 4” hole and put in a 4” circular vent.

Or Do I not have to worry about it cuz (6) 1/2” holes provide enough intake air? My attic is 1800 sf and there are a total of 30 perforated vent parishes in the soffit. I assume all have the (6) holes drilled. I have an attic exhaust fan and a ridge vent. The roofer also installed 3 additional passive roof vents when he did the roof. There is some additional venting under the solid aluminum soffit panels.



Example of one of the holes.

There is also grating under the solid part of the soffit.
 
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Old 04-17-22, 02:57 PM
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So the roof ventilation is a basic calculation, one square ft per three hundred square ft of roof space!

So knowing that do you have sufficient intake and, what you have not commented on is ridge vent?
 
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Old 04-17-22, 05:34 PM
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Soffit vents (intake) and a ridge vent (exhaust) is probably the best way to ventilate an attic.
 
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Old 04-17-22, 06:20 PM
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You have perforated soffits... and you have louvered soffit vents. So you have soffit venting. Even your solid soffit is not an air barrier... air passes all around the edges of it, so it's not really blocking airflow from getting to the original soffit above.

As mentioned, the amount of venting needed is calculated by using a ratio of 1:300.. (some suggest up to 1:150) 1 sq ft of ventilation for every 300 sq ft of attic space. Roughly half of that is intake and half is exhaust. (Which is where the 1:150 comes from) So unless you have done the math, you can't really say that what you currently have is inadequate.

The question is what size are your louvered vents, how many of them are there, and are they plugged by lint and dust? According to the 1:300 ratio above you need at least 3 sq feet of intake in your soffits. So if the vents are 6x12 you would need a total of 6 of them for the entire house. If they are 3x12 you would need 12 of them. The 1/2 inch holes really aren't adding much of anything to the ventilation.

At a minimum I'd remove your louvered vents and either clean them or replace them with new clean ones. If they are clean you probably don't need to do anything at all.
 
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Old 04-18-22, 08:32 AM
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Thank you all for the quick replies. The louvered vents are clogged with what looks like lint. I have no way of knowing how many there are without removing the soffit panels. I think I'm going to take a few more down and explore a little more. When i have the panels removed, I'll use a vacuum to suck the lint out of the louvered vents. there are 6 holes per perforated soffit panel and 30 panels gives me 35.3 sq. in. of intake. plus whatever the louvers provide. i did notice that when the attic fan is running, the smoke from a smoke pen is not pulled into the perforated panels. Maybe my problem is more insulation blocking the vents, than not enough intake area...more investigation required.
 
 

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