This is an important topic. In order to make it a better essay, consider the following.
First, make sure that you have a clear thesis statement and have a road map of where your essay is going, so that the reader will know what to expect.
Second, put in some research on how much money will be saved by considering the window direction and window coverings. Hard data is probably the best way to make your point. The facts are the fact, as they say.
Finally, situate your paper in the context of the need for energy conservation. This can make your point very urgent and applicable for your readers. I will add a link on alternative energy, which can give you some further insights.