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:
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.
Install a thermostat controlled gable fan.
Install soffit vents since I am replacing the plywood anyways.
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.