I have a question Xringer, did you have a particular reason you mounted it to a sheet of metal? Didnt know if you trying to shield it or some other reason other than you had a piece of sheetmetal and it seemed the thing to mount it to.
I have a finished basement and the temperature range from downstairs to upstairs can be significant. I would like to gather some data and see if it is as much as I think it is, or if it would be worth it to rig some kind of switch to run the fan to circulate air.