I've been trying to do it every day lately because it's supposed to be good for your health. I like to open two windows to get a cross breeze going if it's warm enough, but usually it's too cold. It's easy to keep the windows closed for days and days because it's cold, but I like to at least leave them open when we're not home (we have bars on our windows) for a couple of hours each day.

In the summer we probably open our windows less because it's so hot and humid!

What about you? How often do you open your windows year round?