roof turbine – GreenBuildingAdvisor

The answer depends on where you live.

Whirlybird vents rely on the wind for air movement. No wind, they are simply a static vent. Lots of wind without the proper size attic air intake (soffit vent), and they will suck on the house to make up the air that is being pulled out. The results can simply be increased heating or cooling costs created from the conditioned air inside the home being pulled into the attic. Or, in cold climates, it could cause an ice dam issue or even contribute to an increase in attic moisture (attic rain).

If there is a good air barrier between the conditioned space and attic, standard ventilation practices are normally effective.