Advantages of roof air vents include extending the life of a roof and prevention of interior condensation. Disadvantages include the potential to cause roof rot unintentionally.
While older homes can get away without roof air vents, modern energy-efficient homes are likely to benefit from such an installation. This is primarily because older homes are less air-tight than modern constructions. This makes for poor energy conservation, but it does allow the air to flow easily throughout the building. Without this natural air flow, modern homes are more at risk for water condensation. This can lead to wet windows, roof ice dams and even roof rot. Properly operating roof air vents prevent this problem.
Roof vents allow air to move more easily around the home. This means that wet air has the needed opportunity to escape, which can significantly increase the life expectancy of a roof. However, these advantages only hold true if the roof vents are part of an overall well-balanced ventilation system.
If the roof air vents are contributing to a ventilation system that allows too much exhaust while preventing sufficient intake, this can lead to roof rot. In this scenario, the attic takes the heated wet air into the top of the home. This eventually settles on the roof and causes rot over time.