With a new ridge vent installed, I am wondering if these old vents need to be removed? They're plastic covers over a square hole cut in to the attic plywood. enter image description here

Just curious if it will interfere with the air flow; I know I've read some people say gable vents should not be paired with ridge vents. For some reason, the roofer removed the old vents on the other side of the house, but left these ones in.

Adding additional photo to show where the ridge is in relation to the old vents. You can see the old vents in the top right on the back side of the house. enter image description here

  • Assuming the left vent is near the ridge, the right vent seems to be in a strange place, about halfway down the roof. My understanding is that you want half the vent opening area up high (ridge or gable) and half down low (soffet or even near ground level), with nothing in between to "short circuit" convection from bottom to top. If you have too much vent area at the top, air can flow in and out there rather than moving up from below. I'm just an interested layman on this, and could easily be wrong.
    – Armand
    Commented May 13, 2022 at 3:37
  • This other question discusses the "short circuit" issue: diy.stackexchange.com/questions/26379/…
    – Armand
    Commented May 13, 2022 at 3:40
  • @Armand thanks for the link! My old vent is also near the ridge like the one in that other post, so I'll probably ask the roofer to remove it based on that other person's answer. The only difference though is that on the inside my roof there is a plastic rafter vent stapled in between the ceiling beams instead of blown in insulation.
    – sushi
    Commented May 13, 2022 at 4:25

1 Answer 1


The Code says: Attic Ventilation shall be “cross ventilation “ and shall be 1/150th the area that is to be vented. (See ICC R806 Vents.)

However, there is one exception: The attic ventilation can be reduced to 1/300th the area to be vented provided one of the following items are met:

  1. a Class I or II vapor retarder is installed on the “warm-in-winter” side of the ceiling, or

  2. not less than 40% and not more than 50% of the ventilation is located in the upper portion of the attic. The upper portion is defined as: “Upper ventilation shall not be lower than 3’ below the ridge or highest point of the roof. “ (See ICC R806.1.2.)

So, you can see there is clearly a benefit to having ridge vents, gable vents, etc. , but in a proportion that allows COMPLETE CROSS-VENTILATION to the attic.

Depending on where you live, not having soffit vents might be okay. It won’t be as efficient as having soffit vents which gives you good cross ventilation, but it would eventually ventilate, depending on which way the wind blows on your house.

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