Should I add more soffit venting?

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  #1  
Old 03-10-19, 04:14 PM
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Should I add more soffit venting?

Ranch style home with ridge vent/soffits.

I plan on having insulation blown in to increase R value. I just installed baffles in the eaves. I have 4 vents on three sides of the house, and 3 vents on one side. Is this enough or should I add more? I figured maybe adding more vents would help. Would it hurt? Any input?

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Last edited by PJmax; 03-13-19 at 05:28 PM. Reason: resized pictures
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  #2  
Old 03-10-19, 08:32 PM
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We can't see the ridge to know how much vent you have. That said, you need as much area to let air in as you have exhausting it out. If it's a hip roof, the ridge tends to be pretty small.
 
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Old 03-10-19, 09:12 PM
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Trying to upload other pictures is proving difficult at the moment. It is a hip roof.
 
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Old 03-10-19, 09:18 PM
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Yes, as stickshift said, we don't see a gable and looks like soffits all the way around.

Are you experiencing a problem or assuming more vents will help cool the attic?

15 vents and if they are 12" x 12" at 50% NFA (net free area) that would give you 7.5 ft² of low venting which should be sufficient IF those vents share a common soffit space feeding air to all of the rafter cavities.

Again, as ss said, what do you have for high vents?

Also, do you have flat ceilings and a traditional attic floor or any vaulted ceilings?

Before you add more insulation to the attic you need to do some air sealing. Air escaping the house into the attic wastes energy and can cause moisture issues in cold climates. And what is your climate region?

Bud
 
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Old 03-10-19, 09:30 PM
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Flat ceilings. I'm in Buffalo NY. No gable vents, soffits all around with a ridge vent at the top. My concern is that during my baffles install, where the actual soffit vents are on each side of the house, the ones on each end seem too close to where the hips are, thus possibly not letting in enough flow and that maybe installing more that arent so close to the hips, would help with ventilation.

My roof sheathing gets condensation/some mold during cold months due to attic leaks, and insufficient insulation and possibly air flow. I just took care of installing baffles this weekend, before I air seal and blow in insulation just figured I'd see if I was good on ventilation.
 
  #6  
Old 03-10-19, 09:53 PM
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The guidelines are roughly 1 ft² of NFA for every 150 ft² of attic floor. If extremely well sealed (hard to retrofit) they will use 1/300 but the guidelines are very lose so I start with 1/150. If your home has a 1,500 ft² footprint then total high plus low NFA vent area would be 10 ft². That divides half for high and half for low.

Can you estimate the length of your ridge vents. Many ridge vent mfgs state 18in² per linear foot of ridge vent. Example, if you have 20' of ridge vent you would have 360 in² or 2.5 ft². That would be half of what guidance calls for but not terrible.

The real indicator is the moisture you mentioned. Be sure all bath and kitchen vents exhaust to the outside, preferably not out the soffits. If soffit vents are necessary there are better vent covers that send the air down and away.

If you have any ac or heating ducts up there they will need air sealing and insulation.

Bud

Forgot to mention, a hip roof creates an air flow issue with closed off rafter bays. Inside pictures would help.
 
  #7  
Old 03-10-19, 10:17 PM
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I will try to see how long the ridge vent is. My house was built in '57, I dont have any bathroom exhaust fan. Usually open the window for a little bit after showers. I noticed the kitchen exhaust fan (which I believe is original) just blows the air into the attic when it is used and it isn't connected to the roof. I rarely cook, so I just covered the fan grate on the ceiling with plastic for now. The attic bypass only has a flimsy peice of wood as the cover. No heat ducts up there.
- trying to upload pix, but dont see any delete buttons for my old attachments. I read on here that a moderator has to delete my old attachments so I can put new ones?
 
  #8  
Old 03-13-19, 04:20 PM
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I cant tell 100 percent yet, but I'm pretty sure under my aluminum soffit, is the original wooden soffits with little vent holes going around the whole home. I was suspicious so I checked the garage, and under the aluminum there is still wooden soffit. So IF the house still does have the original wooden soffits with small vent holes under the aluminum, should I be wanting to have those removed? I feel like the soffit intake wood be better if the wood was gone.
I started to realize this after looking at old photos of the home, and realizing the fact I couldn't really see daylight as I was in the eaves putting in baffles.
 
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