One thing I get asked about a lot is windows. There are a lot of misconceptions about windows and energy savings, mostly thanks to companies that are interested in selling their products. Here’s an easy thing to do and to see results from: if you have a window that the sun shines directly through in the winter, open the curtains and let the sun shine in! The sun will come through the window and heat the air in your house. The benefit you receive from the sun shining in will FAR outweigh any loss from circulating air touching the window and losing heat. Be sure to close the curtains once the sun has set to retain as much heat as possible. Thermal curtains can help take the chill out of a cold window in the winter.
In fact, when I’m home alone, I like to sit with my computer in a sunny window to stay warm. Then I find I don’t need to turn the heat up as much.
Note that in the summer, if you have windows that the sun shines through you should *close* the curtains, so that the sun doesn’t make the air even hotter! Have you ever noticed how much hotter the air is inside your car than outside when it’s been sitting in the sun for a while? Some of that heat is hot coming through the metal, but most of it is the sun warming the air through the windows. In fact, next time you go to use your car on a cold but sunny afternoon, notice that the air inside the car is actually warmer than the air outside the car. This is a great example of the sun warming the air through the windows.