Upstairs is hot in the summer and cold in the winter ?
Answers:
You need a minimum of 12 inches of insulation in your attic space. 18 is better. You can also have that foil film installed in your attic that reflects the heat from the roof back up and the heat from the house back down. Because in the summer heat get absorbed by the attic space and as the air cools the heat tries to balance the air temperature and is released from the attic and it actually does go down by radiation into the house. The winter thing sounds like not enough insulation.
you really should have a pro come and seal off your attic from the bats too. Bat guano is very in healthy to breath.
Other answers:
Heat Rises
Heat Rises
Have a heating guy come over and evaluate your furnace set up. It could be as simple as not enough vents, or your returns are not working properly...
Good luck.
Metal is a great conductor of heat. That's your problem right there.
simple sounds like you have an issue with insulation. check with local city on the R value for your area then get a pro to check to see what is going on up there. and by the way if you have bats you have a serious health issue on your hands.. call the health department.....