Each house built should keep passive energy systems in mind. Realizing where the sun is in relation to the orientation of the house and the relative direction of the wind, we are able to use certain techniques that can help to cool and heat our houses without any energy at all. For instance, using sun shades over the windows, will allow more sun in during the winter months and less sun in during the summer months. We can also use the wind to keep our houses cool by using cross ventilation. Relatively simple features can increase energy efficiency of our houses.