# Stalling roof turbines to improve air flow?

My landlord claims that roof turbine ventilators move more air when they do not spin—e.g. by stalling it using a piece of wire tied through the vent and the brace. His reasoning, roughly, is that when the turbines are spinning, all it is doing is equalizing the pressure, and claims to observe that the air in the attic is still; whereas when the turbines are stalled, he claims to have observed more air, dust, etc. moving around and leaving the attic.

I fail to see how this could be the case. My understanding of pressure equalizing is that it means that air must be flowing from high pressure (in the attic) to low pressure (outside). By allowing the turbine to spin freely, there would be less resistance/reactive force that keeps the air from moving out of the attic; whereas when the turbine is stopped, the air moving out of the attic wants to move the turbine but it can't (i.e. more resistance). And when something (e.g. wind) spins the turbine, then the turbines will pull air out of the attic; immobilizing the turbine means no air will be pulled out.

I will not be able to correct him if he is wrong (he made up his mind 30+ years ago). But in case I run into anyone else actually interested in a response to his argument, I'd like to be able to explain this better. What would be a more intuitive/straightforward/easy-to-understand/etc. way to explain this?

• I don't suppose 30 years ago he worked for McDonnell-Douglas. Feb 23 '19 at 13:51
• Nope, but he was an air force brat, so he seems to know quite a bit about planes, and can usually tell more about a plane by hearing it than I can by looking at it. Feb 23 '19 at 14:02