Soffit vs DCI SmartVent

I am about to replace the roof on my split level range in northern Virginia. It has a 4/12 pitch, with 24” soffits. There are currently gable vents and a ridge line vent but no soffit vents or gable fan. The current roof is about 20 years old, the old three tab shingles are in rough shape and the current 3/8ths plywood sheathing is very soft in several spots so I am looking at replacing all of it with new 1/2”CDX and Landmark singles. Given that this is big investment, I want to get the ventilation right but every roofer I have spoken with has given me a very different opinion regarding proper ventilation (which coincidentally aligns with whatever product they sell). I know the ridge vent isn’t designed to work with gable vents and should be blocked and replaced with a different intake on the eaves. Here are the recommendations I got:

  1. If you don’t have moisture / mold problems in the attic (which I don’t) then don’t do anything different Soffit vents will likely be ineffective because of the long soffit and insulation blockage, etc.

  2. Install a thermostat controlled gable fan.

  3. Install soffit vents since I am replacing the plywood anyways.

  4. Block the gable vents and install DCI SmartVent at the eaves. I know the DCI SmartVent system has good reviews online and good ventilation should prevent ice dams, but I am don’t see how ice / water won’t back up the SmartVent and into the the 1” channel that they cut into the sheathing.

I’d appreciate an honest recommendation from somebody that isn’t trying to sell me something. Thanks.

The ridge vent isn’t functioning to it’s full potential with the open gable vents. The lower portion of your attic will end up stagnant with respect to air flow. I’d either install soffit vents and baffles in the insulation to allow flow, close off the gable vents and stick with the ridge vent OR just add a gable vent fan and just live with it. The vast majority of roofs I see are not ventilated correctly so you won’t be alone. And it would seem the vast majority of roofing contractors are ill informed on the subject of proper ventilation. That is a bit sad because it isn’t rocket science. While ridge vent works on Bernoulli’s Principle, you don’t have to understand it in order to make it work.

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