Not too big, the mass is in the structure. Mostly wood and roofing shingles.
You can ask any roofer about the weight of those shingles..
I once had a remote La Cross sensor hanging up there about 16" down from the peak,
and I can tell you, it takes a while for the AM sun to heat up the air up there.
Hey! I have not checked that out since we had got the new ridge vent installed. (with the new roof).
It might be interesting to see how effective the mesh type ridge vent is...
And, now we only have one layer of shingles. (versus 2 layers before).
I'm going to go find that sensor..
Yeah, using a dandy WebControl board (with heat sensors etc) should
allow one to tailor the fan motor run time, so it takes out the excess
warm air, without dropping the attic peak's temp down to outdoor levels..
Just harvest the warmest air out of the peak.?.
Yeah, just take the warm air that was going to escape anyways..