Opening Up Blocked Soffit Vents


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Old 05-11-24, 12:51 PM
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Opening Up Blocked Soffit Vents

Hello, I am having new insulation installed in my attic and they are also going to install baffles but they said that my soffits are not open to the attic and that I would need to remove and drill holes to open them up prior to reinstalling (thats not something that they do).

The house is a ranch and measures 30' x 64'. I have a ridge vent installed along the top. I also have triple 4" center vented soffits that extend on average about 24" past the front of the house. Is it possible to achieve the proper ventilation with the current system I have if holes are drilled in the wood behind the soffit? Just based on an online calculator I need 921 sq in. NFVA exhaust and 921 sq in. NFVA intake but I'm not sure what the net free area rating would be of my current soffits. If its possible, how many holes and what size would need to be drilled? I do have mice in the area so not sure if that plays a role in the hole drilling as well.

My handyman whom I trust said he would drill two large holes every other bay on the exterior. Would that be sufficient? Would that pose a potential rodent issue?

He also said he would need to remove the gutter and then the angled metal trim to remove the soffit because the metal trim is so wide on the soffit side (see red circle in pic), that theres no way to bend it back and get at the fastener holding the soffit in place. So that obviously means it would be an expensive job. Is there any easier way to add the sufficient NFVA intake while not looking totally terrible or allowing mice to enter?

Thank you all in advance






 
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Old 05-11-24, 03:35 PM
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You can score the bottom lip of the fascia with a sharp utility knife and bend it back and forth to break it off. Then pull out a piece of soffit, which should slide out the front after you remove the staples. Drill your holes as often as you need. Slide the soffit back in. Then loosen the screws on a 12 ft section of gutter, then slip new fascia cover in, over the top of the old. Then screw your gutter screws right back in where they were.

Then move down and repeat as often as needed.

This may not be your exact brand but it will give you an idea of the net free area of your center vent soffit.

https://www.amerhart.com/product/rol...er-vent-soffit

Each piece has 3.24 sq in of net free per foot. In other words, if your soffit is 24" wide, each piece has 6.48 sq in. So you'd count your pieces and do the math. But don't fret if you're short because soffit is not air tight. Air also is able to move around the front and back edges, which technically are not part of the center vent calculation. Aluminum soffit is by no means air tight.

My guess is that you already have soffit vents in the wood above the aluminum soffit, you just can't see where. What you typically have are a limited amount of rafters that are open. And nowadays most people think more ventilation is better, so they put chutes in EVERY bay, which IMO is just plain wrong. But with the proper amount of ventilation is already cut into the wood soffit that "should be" above your aluminum soffit, then it's okay. You will be reducing the amount of insulation above your top plate when you ventilate every bay, so you are trading one thing for another by doing chutes everywhere.

Full chutes are good when used on modern houses with energy heel (raised heel) trusses because you can still put plenty of insulation between the top plate and the chute. With a house framed like yours is, the ceiling and shingles are simply too close together to have the best of both worlds. By increasing ventilation you reduce insulation and increase heat loss on the entire house perimeter.
 
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Old 05-11-24, 04:46 PM
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Thank you for the reply!

So right now I have batt insulation in the attic and no baffles. I am having all the batt insulation removed, baffles installed, and then the cellulose blown in.

Lets assume there is full plywood behind the soffits with no holes drilled at all (which wouldnt suprise me with this house since I've already discovered a lot of corners cut). If thats the case, how many holes per bay and what size would you recommend? And would that be a potential rodent entry point or probably not with the soffits going back up?

My guy said he would do two large holes every other bay but not sure how that would affect the net free area calculations. I'm assuming the 6.48 sq in rating you gave as an example is assuming its fully open underneath all soffits. So I guess I need help determining how drilling holes factors into those calculations.

Thank you!
 
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Old 05-11-24, 10:51 PM
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Soffit ventilation louvers usually have screen to prevent those sort of problems. So you likely wouldn't just want to cut holes here and there and invite who knows what into your attic.

Houses typically have several 6x12 louvers per side, roughly every 8 feet, but you do the math to figure what you need. At 72 sq inches each that is only about 6 louvers per side.

It's also possible you have 2" continuous vents, another popular style. Hard to say with no crystal ball.
 
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Old 05-12-24, 10:48 AM
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Just out of curiosity, would it be possible to just cut out a hole out of the existing soffits, cut into the plywood underneath, and then install 16x8 louver vents like pic below? Or would that look terrible? Just trying to thing of an alternative that doesnt invovle disassembling the whole thing (gutter, trim piece, etc).


 
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Old 05-12-24, 12:51 PM
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You could, it's your house. Bugs and wasps will be able to bypass those screens.
 
 

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