In this design of a passive solar house there is on wall that will provide all the heat and light you need to live in the house or "room." In the picture below it will show you that the summer sun is higher than the winter sun. So there is a small slope hanging off the edge of the house that will get the right ammount of sun and not to much heat from the sun. Also the wal that is heated in the winter is designed that the will get all its enegry and will heat the house at the right temp.