If you're not ready to make some major (expensive) changes to your home, I have some poor-man ideas that might improve the hot/cold issue.
- Your sf. suggests that you can move all of your regularly used living spaces downstairs, and less used upstairs. It's less expensive to heat or cool a single guest room than the entire upstairs.
- Install a door at the top of the stairs with weather stripping, so your heating/cooling efforts downstairs stays there.
- Use insulated curtains or shades on the sun side of the house.
- Use magnetic storm windows until you are ready to replace the old ones.
- And like Wise Will said, vent your roof.
