From what I've read, curtains don't do much to retain heat. For that, you want thermal shutters with weatherstripping around them to seal the window at night.
I know that to keep a house cool in the summer they say it's best to block the sun before it gets through the glass– things like blinds, shades, etc that are inside absorb the sun and radiate the heat into the house. I would think the same would be true in winter, though you might not gain as much in the day as you would with drapes open, since some of the heat can radiate back through the glass and with them open the sun penetratets deeper into the room. |