# Have soffit vents? Check them.



## captfl2x (Aug 25, 2016)

Alabama last 2 weeks temps of 92-96 degrees. Because of soil type, almost all homes are on slabs. HVAC are in attics. I have an older home and last few years I've had more insulation blown in (twice). The ranch style hip roof leaves very little vertical height to work in. My HVAC over works with a setting of 77 degrees with these high temps. I was curious if I had insulation blocking any soffit vents or preventing air flow to attic. Including the attached, floored, and non insulated garage, there is a total of (35) 8" x 16" soffit vents. When I pulled the firs vent, I knew there was a problem with the vents. The vent opening was only 6" x 12". Worst than that was the vent had about 90% blockage with paint and "crud". All vents had an estimated blockage of 30% to 90%. All vents were replaced with new. Instead of each vent being placed between rafters, 27 of the 35 vents had a 2"x4" blocking the opening. So each of these had opening loss of 6 square inches. Over the next few weeks, I will add 13 additional vents to reach the desired "free air flow" square footage. I wish I had taken attic temp readings before and after---but didn't. I do know that the HVAC is cycling more and the non insulated garage is even cooler now.


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## Nealtw (Jun 22, 2017)

captfl2x said:


> Alabama last 2 weeks temps of 92-96 degrees. Because of soil type, almost all homes are on slabs. HVAC are in attics. I have an older home and last few years I've had more insulation blown in (twice). The ranch style hip roof leaves very little vertical height to work in. My HVAC over works with a setting of 77 degrees with these high temps. I was curious if I had insulation blocking any soffit vents or preventing air flow to attic. Including the attached, floored, and non insulated garage, there is a total of (35) 8" x 16" soffit vents. When I pulled the firs vent, I knew there was a problem with the vents. The vent opening was only 6" x 12". Worst than that was the vent had about 90% blockage with paint and "crud". All vents had an estimated blockage of 30% to 90%. All vents were replaced with new. Instead of each vent being placed between rafters, 27 of the 35 vents had a 2"x4" blocking the opening. So each of these had opening loss of 6 square inches. Over the next few weeks, I will add 13 additional vents to reach the desired "free air flow" square footage. I wish I had taken attic temp readings before and after---but didn't. I do know that the HVAC is cycling more and the non insulated garage is even cooler now.


Do you ave air chutes in every bay between rafters?


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## Gymschu (Dec 12, 2010)

I'm a painter and on a recent house repaint, I offered to replace paint-blocked vents. Much to my surprise, half of them were just "dummie" vents. Someone just screwed the vents into soffit wood and didn't bother to cut out the wood so there would be air flow!!! I would say UNBELIEVABLE, but knowing how GC's operate and/or a subcontractor on a time schedule works, it's more common than you'd think. Glad you're getting your blocked vents taken care of.


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## captfl2x (Aug 25, 2016)

No air chutes except where some remodeling was done with access to where chutes could be added. I cleared 2 areas at the top wall plates. all the rest were good. Adding air chutes else where means insulation would be destroyed again. Decided against it.


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## Nealtw (Jun 22, 2017)

captfl2x said:


> No air chutes except where some remodeling was done with access to where chutes could be added. I cleared 2 areas at the top wall plates. all the rest were good. Adding air chutes else where means insulation would be destroyed again. Decided against it.



Then don't calculate the vents, calculate the square inches of the chutes.
Usually you have air chutes with just enough bat insulation under it over the wall to hold the loose in place,


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## Gregsoldtruck79 (Dec 21, 2017)

Good thread....

Here is another one to watch out for, if your home had the standard of 3/8 " plywood level soffits and then a contractor has encapsulated it with vinyl/metal. As they did on our 1960 model home, way long before we bought it. . 

While working on our hot attic issue, I pulled one of the "perforated" vinyl soffit panels out to check to see the condition of the original soffit vents that should have been located right above the perforated vinyl air intake panel. 

I found the original old 8" x 16 " metal vent in the old plywood, with only about 4 inches of one end of it, being ventilated through the perforated vinyl panel. So in the pic, I just installed another perforated panel beside it to get the old vents full ventilation used. All while thinking maybe the house just had one vent covered.  Nope....

After checking all the rest of our homes level soffits perforated vinyl vents, I found that 6 more of them were not even close to the old original 8" x 16" soffit vent. So I spent some time cutting in more 8" x 16" soffit vents centered over the top of vinyl perforated panels.


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## AtticFoil.com (Aug 27, 2013)

I've seen it all too. I did a video in 2014 on exactly this topic. Fortunately with continuous soffit vents, the issue has gotten better.

Attic Ventilation Troubleshooting:


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## steves7839 (Aug 18, 2019)

I recently discovered 6x12" vent holes hiding behind my 8x16" soffit vents. We have a continuous ridge vent 76' long. The ridge vent NFA (Net Free Area) is about 1370 square inches. New 16x8 soffit vents have a NFA of 65 sq" each. To balance the ridge vent area I should have 21 soffit vents. Only 14 were installed. 

The soffit is 1/4" cement board, and I've destroyed a couple of wood saw blades enlarging two soffit vents. I'm tempted to use a rotary masonry blade on plunge cut, but nervous about what I might cut across (or breathe).


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## captfl2x (Aug 25, 2016)

I've cut a lot of cement board with a masonry blade. Get a really good filter face mask and safety glasses that wrap around your eyes. When I cut my vents with a saw blade, I made sure that my circular saw blade cut only about 1/4" deeper than the plywood thickness. Didn't hit anything. I stayed clear of known HVAC line and known TV cables.


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## turboflush (Feb 1, 2016)

steves7839 said:


> I recently discovered 6x12" vent holes hiding behind my 8x16" soffit vents. We have a continuous ridge vent 76' long. The ridge vent NFA (Net Free Area) is about 1370 square inches. New 16x8 soffit vents have a NFA of 65 sq" each. To balance the ridge vent area I should have 21 soffit vents. Only 14 were installed.
> 
> The soffit is 1/4" cement board, and I've destroyed a couple of wood saw blades enlarging two soffit vents. I'm tempted to use a rotary masonry blade on plunge cut, but nervous about what I might cut across (or breathe).



get a cement blade for the circ saw... Diablo!! dont bother with cheap ones.


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