I have installed all types of ventilation. The least expensive are small 9”x9” vents. The most common are turbines. Turbines have improved since I got in the business. We used to install turbines with steel ball bearings, these would later become noisy. Lomanco has ball bearings that are lubricated and incased in hard plastic that will never make a noise. Then there are electric turbines that operate with a thermostat. I do not like these because the Texas heat requires that they are on often, and the thermostats tend to burn out in about 5 years.
My favorite ventilation is ridge venting. This requires that the plywood is cut back and the shingles are installed on top of the venting. It also requires that the home has effective soffit venting that is clear from insulation. In a newer home, the insulation contractors will usually install plastic to keep the vents clear. If these intakes are clear, then air will flow to the peak of the roof. This will allow for the insulation to breath.
If a roof is not insulated properly the roofing material will not last as long. Recently, I inspected a 40 year roof on an expensive home. The roof was about 8 years old, however the ventilation was poor and the roof was experiencing thermal cracking. The material was full of cracks and curling as a result. This was also causing de-granulation, or the minerals on the shingles were coming off. The minerals are there to protect the asphalt. Once the asphalt is exposed to the sun, the UV rays will deteriorate the roof at a rapid rate. It is advisable to use a ventilation chart to determine how many feet or how many vents needed. Later I will discuss the importance of proper ventilation and its effect on the house. Jeff