You know, back when it was cold out (and, this being Colorado, that was last month), my south-facing windows were awesome. They let in tons of light and kept the entire place snug and warm. I barely even needed to break out the blankets!
But Colorado's weather likes to mess with you, so it recently decided that it was done with the 50s and jumped right into the 90s. And those lovely south-facing windows that kept my house so warm in the winter are still keeping my house warm. Unsurprisingly, I appreciated this somewhat less.
So when I checked out the Energy Savers Tips page for Windows I was not surprised to hear that it suggests keeping your south-facing windows unshaded in the winter and using curtains in the summer. But there are a lot of other things you can do, too—by installing awnings or sun-control films, you can also reduce the amount of solar gain (which, during this time of the year, is better known as smoldering summer heat.)
In any case, this is kind of disappointing, because our new Energy 101: Daylighting video explains that south-facing windows are best for daylighting. They let in the light all day long, and don't have as many problems with glare and heat as east- and west-facing windows do. So I guess it could certainly be worse.
But it sounds like I just need to keep playing with the curtains until I figure out that nice balance between letting in the sunlight and letting in the heat!