As a builder in a much milder climate (2000' 40-60" snow annually) I wouldn't see the point of allowing the thing to create negative pressure in a cold environment. If the roof is fully vented otherwise, as in full soffit and ridge vents, then the only purpose of the turbine is to cool the space by venting excess heat. If the house is inadequately insulated, and the roof is poorly vented, then the turbine might be instrumental in preventing ice dams and needs to be in operation to prevent damage. Obviously, that would be a little tough to determine without a visual inspection. Personally, I would carve a nice foam plug for the underside of the turbine,plug it, and let it rest for the winter, while being very vigilant as to how it affects the performance of the ventilation. I would hope that any online battles you read of regarding this issue are limited to controlling ice damming, as the thing is undoubtedly contributing greatly to negative pressurization and the "chimney effect" and sucking pretty hard on your wallet on these nasty winter days. Good luck