I've taken a lot of classes about how to design buildings. One thing that sticks out to me is how good trees are. What the crap does that have to do with building right? Well, not a lot, but it sure has to do with how hot or cool your building is. And you know how great trees are right? They eat the CO2, and are great for the environment. But there is more than just filling your yard with trees.
The winter is cold, and so you want to be warm. Winter wind is horrible; if your door faces north you know this is true. So how do we counter this, besides never having a door on the north? Trees. Evergreens, such as the look of Christmas trees, never get bare. The whole year long they are in full force protecting what is around them. If stuck on the north side of the house they protect from that wind threatening to destroy.
These are okay kind of plants, but the best are the kind that shred their leaves. They want to be on the south side of the house. During the winter they do not have leaves, and so they let the sun come hit the house. The sun is mostly on the south side of the house all day, so it gets the most heat gain there. The summer is hot, and so you do not want the heat gain, which is why these trees are so great. In the summer months they are in full bloom, shading the house from the sun. I know you like to sit in the sun; shouldn't you let your house as well?
I would love to report that I do this. I do not. My father is kind of in charge of the yard, and somehow is not in favor of what trees leave behind. Slowly all the trees in our yard have left. However, this is going to be one of the first things I do when I get a house for myself, plant trees.
The Arbor Day Foundation will give you 10 free trees with a free membership. Totally worth checking out!