"Ridge vents work with soffit vents, and suck air in the bottom and out the top. Gable vents work with other gable vents, and air blows in one, and out the other. Mixing the two makes the situation complicated. A single gable vent and a ridge vent is certainly better than just the ridge vent, but probably not as good as either a pair of gables at opposite ends of the house, or a matched set of ridge and soffit vents. Do you only have one open gable? If you have two, and they're working, why are you installing a ridge vent? "
Our roof was replaced 12 years ago. The original roof had gable vents and soffit vents, no can vents. The outfit that replaced the roof installed can vents. One section of the roof already needs to be replaced. I had a different roofer come out to assess why. He said cause was condensation due to improper venting, and that the cause of the improper venting was that the gable vents were not blocked off when the can vents were installed. According to him, having both gable and can vents made both less effective. Being ignorant about all this, I'm trying to get some confirmation that what he told me is in the realm of possibility. The roof obviously need to be replaced in any case, but I'd like to be able to make sure that we don't just have the same problem. There's also the question of whether or not the people who installed the roof failed to do it properly.
Thanks in advance for your assistance.