History: The first traceable concepts of environmental designs focused primarily on solar heating, which began in Ancient Greece around 500 BCE. At the time, most of Greece had exhausted its supply of wood for fuel, leading architects to design houses that would capture the solar energy of the sun. The Greeks understood that the position of the sun varies throughout the year. For a latitude of 40 degrees in summer the sun is high in the south, at an angle of 70 degrees at the zenith, while in winter, the sun travels a lower trajectory, with a zenith of 26 degrees. Greek houses were built with south-facing façades which received little to no sun in the summer but would receive full sun in the winter, warming the house. Additionally, the southern orientation also protected the house from the colder northern winds. This clever arrangement of buildings influenced the use of the grid pattern of ancient cities. With the North-South orientation of the houses, the streets of Greek cities mainly ran East-West. The practice of solar architecture continued with the Romans, who similarly had deforested much of their native Italian Peninsula by the first century BCE. The Roman heliocaminus, literally 'solar furnace', functioned with the same aspects of the earlier Greek houses