I.have one in my house, it is going to be removed in the near future. It works good some days, but modern ac is still better. When we use the ac it lets hot air from the attic in, and worse all winter it is letting cold air from the attic in. The thing can really be insulated.

There is a lot about this house that needs to be updated to modern energy standards and getting rid of that fan is on the list. Overall it costs far more than it saves.