Please rank exhaust vents good, better and best.

Ranking the types of attic exhaust vents: Good: Wind turbines, gable louvers, and roof louvers. Better: Power vents. Best: Ridge vents.

Good: Wind turbines, gable louvers, and roof louvers. Better: Power vents. Best: Ridge vents. The best system in terms of performance (ventilating the entire underside of the roof deck continuously without any moving parts or using any electricity; and without leaving any dead unventilated areas in the attic), appearance (not very noticeable from the street), and cost (factoring in time and labor to install) is a ridge vent system. The next (better) would be a power vent with a thermostat and a humidistat. The power vent will ventilate whenever necessary, summer and winter. Power vents are capable of reducing the temperature in an attic in the summertime by more than any other vent. A power vent provides the largest amount of air changes through an attic space. However, power vents have moving parts that can eventually fail or wear out. And power vents leave sections of the attic unvented. All remaining exhaust vents (roof louvers, off-ridge vents, gable louvers and wind turbines) are OK. Not great but good. This category of exhaust vent is highly dependent on the wind direction to determine how they will function. Also, they are localized vents, which means that they can leave hot spots in the attic. An externally baffled ridge vent is the optimum choice provided that there is sufficient horizontal length of ridge for the size of the structure. In addition, the wind flow over the product helps draw more heat from the attic compared to the heat exhausted from the attic through thermal buoyancy only. The ridge vent also allows for the entire underside of the roof deck to be ventilated if used with continuous intake venting. Powered attic vents can move the most air through the attic space, but this comes at a monthly cost (the cost to operate about 3 or 4 60W light bulbs). If the structure is being built in a heavily wooded area where there is little wind or if it incorporates a tall hip roof, then it may be best to utilize a powered attic ventilator.