Roof Vegetation Makes Residential Houses Cooler and More Energy Efficient.

Guam, a tropical island in the Western Pacific, populated by 180,000 people serves as year round destinations for 1.5 million tourists annually. Because of typhoons and earthquakes most walls and roofs of residential and commercial buildings are constructed from solid concrete that accumulates a massive amount of heat. The objective of this study was to determine the magnitude of temperature reduction resulting from the presence of vegetation covering the roof top and using this information to estimate energy savings.  Collected data indicated that vegetation on the roof reduced indoor temperature by 5-7^oC for at least 12 hours a day year-round. On Guam, typical energy consumption of a residential house with the air-conditioner maintained at 24^oC oscillates around 2000kWh per month. The use of roof vegetation cuts the total energy consumption by half. Since the price of electricity on Guam is very high, the benefit of roof vegetation could be significant. Details related to temperature fluctuation and vegetation resilience to typhoons accompanied by immense tropical rainfall will be also presented and discussed.