Utilization of Turf for Green Roofs in the Tropical Island of Guam.

On the island of Guam air temperatures as well as the daily amount of solar heat are nearly constant year round. Because of frequent and strong typhoons most roofs are 20-25 cm thick poured concrete, usually slightly pitched or flat with no attic space or dropped ceilings inside. Daytime temperatures for concrete roof surfaces reach around 40oC and overnight temperatures cool to around 30oC. Most residential houses and other buildings use air conditioning continuously. The establishment of suitable turf on the roofs of residential houses may reduce temperatures by 7-9oC, therefore significantly reducing the amount of heat stored in 30-40 m3 of roof concrete to be offset by house air-conditioning systems. A real challenge are typhoons with winds exceeding 200 km h -1 threatening the resilience of green roofs. Several turf species were tested. Slow growing Zoysia tenuifolia with its dense root system anchored into metal mesh affixed to the roof surface is the most promising. Data and discussion will be presented.