Proper opening for 4 x 16 soffit vents

I just discovered that the roofer cut 3 - 2 3/4” round holes per 4x16 soffit vents not the full vent.
I’ve got mold and bad to no ventilation in my 1064 sq ft attic. I have basically 56 holes of the same size for ventilation.
If this the usual way that roofer cut vent holes for 4 x 16 vents?

I would assume the same size hole for the same sized vent but do the numbers and ease your mind. Overall, you have approximately 2.3 sq ft of soffit intake drawing air for the whole attic if you combine the area of all the holes. That is lots of intake! A standard attic vent is generally 50 sq in (~.35 sq ft) and one vent services 300 sq ft of attic space. 1064 / 300 = 3.54 vents. Roundup to 4 vents and you have 1.39 sq ft exhausting airflow serviced by 2.3 sq ft fresh air intake. You’re fine.

I think my math should be fairly accurate but double check.

Next, I’ll take the “Celebrity pike lures” category for $400 please?

Thanks for the math Ivoman. My ridge vent has an NFA of about 470. That’s 12.7 NFA for 37 feet.

Wouldn’t this be a big imbalance? My understanding is that while the soffit vents can be overdone, the ridge vent should be equal or less to get the draft or ventilation to work.

Right now there is no breeze or hint of outside air coming in.

It’s a static system, it works when it has to work.

Have you smoke tested the attic with an incense stick to see if air exchange is indeed occurring?

Should I have a lawyer review this comment first so I’m not being blamed for someone’s house being burnt down? :grimacing:

No lawyers needed!

I tried this, no flow, no breeze just moist air that I can’t get rid of. Temp in attic same as outside.
Hotter than hot in summer.
Humidity outside 38%, house 48%, attic 90%. I’m going with increasing the soffit openings as a start.

Don’t worry about the 1 in 300 rule, it’s bullshit.

An attic space is not a 2 dimensional surface it’s 3 dimensional so it has volume which varies directly with the pitch of to roof, the 1 in 300 rule doesn’t take this into account.

To fix your ventilation the best you can without resorting to rather invasive things like installing rafter vents is to put an intake vents between each and every rafter ideally remove the entire wood soffit and replace with something vented or install standard vent strips.

Drilling holes is inadequate unless they are 4" holes and you would need more than two 4" holes per rafter bay.

Install a ridgevent on the entire length of your ridge.

It will work better if you close off the ridge and install a power vent so long as your intake path is clear but this is usually not needed.

You can only work with what you have and the house is built the way it’s built.

The 1 in 300 rule is for salesmen to sound like they know what they are talking about.

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Does a non ventilated roof cause shingles to curl and fail?

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Wow, this thread went south pretty fast.

As an update to my original thread, the roofer who installed my roof will be cutting the 14 4 x 16 vents to their total size giving me 26 NFA, at least that’s the spec on them, vs the current three 2 5/8 holes per vent of about 2 to 3 NFA per hole. This along with my 14 existing 3” vents should give me a 300 intake for my 1064 sq ft attic. My attic has a 8/12 pitch so 20% more is required to the 1:300 calc of 255. So this puts me on target.
The ridge vent, which was cut to an average 1 1/4” for 37 feet, the entire run of the roof less 12”, is at 12.7 a foot or about 470 NFA. Ive reduced that due to the smaller cut to about 350. Still an imbalance but better than the 160 I had before the mods.

I got Quarrix rep involved very early in this and cc’d the roofer. Quarrix was great with their take on things and made the recommended change suggestions. While Quarrix was not able to force the roofer to comply I suggested he try just cutting out the vents he installed to their full size and that alone might fix the issue. If not he has to replace the ridge vent and install properly potentially with more intake vents.

Hopefully this will work. My need more soffit air or a ridge replacement. Just not sure.