After our cars and our homes, our heating and cooling systems are the most expensive thing most of us own. Yet, unlike our cars, we don’t think about it until it breaks. It’s in a closet, or the basement, quietly working to keep us comfortable, and as long as that is true, we ignore it. But doesn’t it make sense to take care of it, so it works more efficiently and lasts longer? Here are some simple steps you can take to keep your system in good shape.