I live in the mountains of Western North Carolina in a very nice house built as a second home by a well-off couple in Atlanta, Georgia (about 2 hours away). It’s a so-called “three-season home,” not really suitable for winter occupancy. There are many windows, especially on the south side (seasonal view of a lake and the mountains beyond after the leaves fall), which is excellent for passive solar heating when the winter sun is low on the southern horizon. However, all that exposed glass feels very cold inside (“radiant cooling”) even when the thermostat says it’s 64 F.
I installed 4″ plantation blinds on the windows a few years ago. When I close the blinds in the winter, they block the exposed glass, and it feels a little warmer inside. I keep the blinds in about half the windows of the house in the wintertime. It’s like a whole new, very cozy home.
I experimented with the idea to stuff some insulation in the 4-6″ gap between the window and the blinds. If the blinds are closed you don’t notice the insulation at all. (It looks pretty redneck from the outside – but who cares!?) I purchased some 4×6 foot sheets of 4-inch rigid styrofoam insulation at the hardware store, cut it to fit the window openings (very easy to cut with a hand saw, a tactical knife, or even a large jagged kitchen knife), and wrapped each block with a linen-type burlap ~ stapled the edges tight with a heavy-duty plier stapler. After I install the “moveable insulation” my utility bills drop by half!
I haul the insulation out of the storage room in the basement for the hottest weeks of the summer, too. Blocking all the glaring-bright light makes the house feel cool, a shelter from the elements! Again, the utility bills drop by half!