It just has to be spun by a small DC motor, but what metal would be good for making a small propeller?
both a good but have an energy survey on your place and see which one is needed mostmost power companies will do it free or very cheap but a thermal camera will help you make the decisionand put baby powder around your windows and see if they blow around any.
In most cases you have a floor covering(rug) or even linoleum which is a barrier Now heat rises and the most heat is at the ceiling, so the next thing closest to the ceiling is the Window if it is crappy windows, then window replacement would be next on my list.(after the attic is well insulated first)
Either copper or aluminum, when formed, copper will hold it's shape better and is easy to workAluminum is also pretty easy to work if you can get a soft grade, and yes, it does come in different grades If you have to form and fasten the individual blades to a hub, then copper is the best choice as it can be soldered easily.
