CAIRO - Atop his permanently unfinished rooftop in Cairo's Manshiyet Nasser District, Hanna Fathy twists the spigot of his homemade solar heater. A trickle of hot water cascades to the dust-swept floor as the blazing sun sinks on the horizon.

Hanna Fathy demonstrates a water...
Posted August 26, 2008 | 03:19 PM (EST)