Welcome to ER, again
I have family in NC, in an old house from 1936 iirc. After moving in the two things that helped the most with heating/cooling were:
- Replacing old single pane windows with argon filled double pane. This brought the temperature up about 3-5°F in the winter and greatly reduced drafts and gas usage. Also made it easier to cool in the summer and reduced A/C usage.
- Insulation in the attic. It became noticeably cooler upstairs during the summer and also reduced bills year-round.
#1 is probably too expensive for you to invest in a rental house, but maybe you could talk to the landlord about it? Maybe propose that if he replaces the windows with low-e models, then you'll insulate the attic. IF that doesn't work, then try
making interior storm windows.
You could also ask the landlord about doing an energy audit. This would tell him what to do in the future, while could implement any of the cheaper suggestions.