There are a variety of initiatives to increase the energy efficiency of buildings.

One mechanism proposed here is to use an exterior of organic materials to radiate excess heat through the evaporation of waste water from the building--much like humans sweat to reduce our internal temperature.

Many buildings in Bombay are covered with Moss during the monsoon, and dry up during the hot summer months. But what if waste water produced within the building could be used to sustain this moss growth year round? The moss could help purifywater, cool the building, and provide a beautiful exterior. The difficulty would be in designing a water distribution system for the exterior, and a building material that suits moss growth.

Bamboo
Another possibility is to cover buildings with bamboo panels, which would be highly cost effective. Water could be allowed to flow through the bamboo at a regular rate, facilitating the growth of vines and other plants.

Other possibilities with Bamboo include developing structurally engineered building methods for building inexpensive, reconfigurable housing structures.

Great Article on Bamboo Building Techniques