NELLIE PEYTON and CHRISTOPHE VAN DER PERRE CONSTRUCTION is booming in Dakar, where unfinished apartment blocks tower over most streets, their exposed concrete bricks a dull uniform grey. In one site, however, a building stands out - the bricks the workers are laying are made of raw, red earth. Concrete is inexpensive and used with abandon in Senegal's capital, but it is poorly suited to the West African heat. On summer days, when temperatures frequently reach 100 degrees fahrenheit (38°C), the buildings become furnaces, cooled only with blasts of air conditioning. Earth naturally regulates heat and humidity, say the founders…