Turbine Vent

A turbine vent is a rotating cap fitted at the highest point of a roof. Wind spins it, and so does the warm air already rising inside the building, since hot air is lighter than cool air and climbs to the top of any space it is in - an effect often called the stack effect. Between them they pull the hottest, stalest air out through the ridge. Nothing is plugged in and there is nothing to set.

A vent is only an outlet, and an outlet needs an inlet. Openings low down on the opposite side of the space, of an area to match, let cool air in as the warm air leaves; without them the turbine turns in the wind and almost no air changes. That failure hides itself, because a spinning turbine looks like a working one. The two drivers can also fail at the same moment: still air removes the wind, and hot outside air removes the temperature difference. That happens on a calm, hot afternoon, which is exactly when the cooling was wanted. So the device lowers the general temperature of a space rather than holding it at a chosen one, and below that floor a powered fan is what actually moves air.

Because nothing regulates it, a plain turbine cannot be shut. Without a damper or a cover put on for the cold season it keeps drawing warm, moist air out all year, so the warm-season benefit becomes a cold-season cost. The unit is also a moving bearing set in a hole cut through the weatherproof layer of a roof: the flashing around it is a permanent leak path that needs checking at every roof inspection, and where the same roof collects rainwater the penetration sits above the catchment. The bearing wears in weather and dust, which gives a turbine a shorter working life than a fixed vent cap with nothing to turn. Check too that the low inlets are still open, since they are lost to stacked crates, a crop grown up in front of them or drifted debris far more often than the turbine ever seizes.