I'm going to tear mine out. It helps a little, but it leaks so much conditioned air when not in use i'm convinced it is a negative overall.

tear it out and put a new one. There are models from airscape that come with motorized dumper doors with insulation. When fan is off, it's sealed.

Thanks for that. I wasn't even aware that I had an option to get one that wasn't sending all my winter heat out.

Yes. It's really amazing. First thing that I did after bought house last summer was to install whole house fan. Due to it we used hvac to cool house for less than 36 hours in July-October timeframe (only at days when temperatures were above 40 for few days in a row or when night temperatures didn't went down below 20)