We have a house about 45 years old and are thinking about replacing the roof. We currently have 4 standard vents that were originally installed. Based on research and feedback, we have been told we need approximately 8 vents by one contractor, not adding any by someone else, or adding a ridge vent across the top peak of the house by another contractor. We have approximately 2,000 square feet. What is the best option?
It depends on the situation.
But usually, a ridge vent with soffit vents will work just fine. Sometimes additional gable vents and or powered roof vents are needed. See link in signature below for more information.
It really depends on the style and shape of the roof. A ridge vent on a hip roof is pretty much useless.