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New Hidden Vent Soffit - Additional Vent Baffles Needed?

New Hidden Vent Soffit - Additional Vent Baffles Needed?


  #1  
Old 04-19-21, 10:24 AM
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New Hidden Vent Soffit - Additional Vent Baffles Needed?

A couple of years ago the vinyl soffit panels on my house were replaced as part of a siding/roof project. The old soffit was mostly solid panels with vent panels (w/perforated holes) every 5-ft or so. The new soffit panels are Ply Gem Mastic Ventura hidden vent type, basically a pair of slim horizontal slots every 3-1/2" instead of the occasional vent panel..

Last summer it seemed like the attic ran hotter and the top floor's HVAC had a harder time keeping up. I recently looked in the attic and saw that when the house was built in 1995 they evidently only put vent baffles between trusses lining up with where the old soffit's vent panels were. Other spaces has insulation right up against the roof sheathing. With these new evenly spaced soffit vent slots it seems to me I should add baffles between every truss now, correct?

I just installed one of the 4-ft black plastic baffles from Lowes. It took quite a bit of effort, so before I go to all that trouble to do more I want to be sure I'm not doing something inadvisable or unproductive.

 
  #2  
Old 04-19-21, 01:42 PM
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So you have soffit venting, what else, ridge vents?

The formula is 1 sq ft ov vent per 300 sq ft of attic space!
 
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Old 04-19-21, 02:53 PM
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There are those who think that more ventilation (more than the standard 1:300 ratio) is better. I'm not one of those. Some may depend on the climate you are in, but if you live in an area where it is half heating, half cooling... you should stick with the standard ratio.

Soffit is not air tight, air passes around the edges of even the solid panels. So I doubt your change has much to do with your ventilation or the change in soffit style. Probably more a result of the color of the new shingles, if different from the old ones.
 
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Old 04-19-21, 03:03 PM
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So you have soffit venting, what else, ridge vents?
Not ridge vents, but rather there is a line of six roof vents up near the ridge. They look similar to the 50-60 sq in square roof vents on the HD website.



 
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Old 04-19-21, 03:15 PM
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Soffit is not air tight, air passes around the edges of even the solid panels. So I doubt your change has much to do with your ventilation. Probably more a result of the color of the new shingles, if different from the old ones.
Good point, and actually the shingle color was my first thought when I first noticed things seemed hotter. They are slightly darker than before, but not black. So that would certainly contribute.

Worrying about the baffles may be all for naught anyway... After I first posted I went back up into the attic this afternoon and determined that this 67-year old man can no longer access a majority of my attic. Even 25 years ago when I first crawled around up there to install an attic TV antenna it was a chore climbing past duct work, but now it seems about physically impossible for me.

So about all I can access will be about 10-feet of space around the attic hatch which would let me install 3 or 4 more baffles at the most. That would have to do unless I come to the conclusion that it won't be enough and I need to hire somebody in.

On a positive note, right before I went back up this afternoon a strong cold front passed through and I was happy to be able to feel a light draft of cooler air coming out of the top of the new baffle I installed earlier, so it seems it was worth the effort. I was also happy to spot a few more existing baffles than I first saw. However the only one I could see down was mostly obstructed by insulation at the soffit end. I was able to poke a long piece of 1x3 lumber down into it to open it up some more so hopefully that will help some too..

So I guess I'm going to add a couple of more baffles where I can manage to reach and hope that's going to be good enough to keep things reasonable.

 
  #6  
Old 04-21-21, 01:06 PM
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As previously mentioned, I'm having trouble accessing a majority of my tight attic space due to my old age and ductwork being in the way. It was disturbing to me that the one original rafter baffle I was able to see down was mostly obstructed by insulation at the soffit end, so of course I'm imagining the worst for the others. So tomorrow I'm going to try to go back up and install 2 or 3 more of the black plastic proVent baffles from Lowes between previously un-baffled truss spaces that I can reach near the access hatch.

Below is a picture of what I have. On the right side of this truss you can see where an HVAC condensate line passes under some Romex and penetrates out towards the soffit cavity. There appears to be a 90-degree elbow that turns down into the top plate where the line travels down inside the exterior wall before exiting just above ground level. (Although the sheathing looks notched out above the elbow, I think it's just daytime light shining up on the sheathing from the white soffit below.)

Mainly I just want to be sure what I'm doing is OK. As you can see the insulation goes right up against the roof sheathing and appears to stop right at the soffit cavity. When I installed the first new baffle the other day I used a 6-ft 1x3 to reach out under the low pitched roof and press down on the insulation enough to jam the baffle in place. I noticed the insulation seemed to be a little stuck to the sheathing. It may have been stapled, or it may have just gotten stuck over 25 years, I couldn't say for sure. The insulation ended up snug against the bottom of the new baffle seemingly holding it tight to the roof, and I only stapled the new baffle to the sheathing at the top. Seems fine, but I wanted to confirm I'm not doing anything dumb.


 

Last edited by vblg01; 04-21-21 at 02:49 PM.
 

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