Hello!

When we bought our house a couple years ago, I took down all of the previous owners' curtains and gave them away on freecycle.. I love the clean look of having no curtains, and all the light that comes in. However, we live in PA and i'm realizing it is a big waste of heat in the winter (and somewhat a waste of the AC in summer) to have no curtains. So I'm looking into them. My question is, it is helpful enough to simply get curtains of a reasonably thick material, or, for insulating benefits, should I really go with curtains sold as "thermal" or insulating? I'm sure thermal must be better, but how significantly better? Any suggestions for a good online source? Is it easy to add a thermal layer behind curtains? (i'm looking at the "tab top" style) Our big living room and dining room windows bow out, so unfortunately i think i have to go with curtains rather than shades.

thanks