The house is specially designed to be easily transported. In this design each part is prefabricated and shipped together--even the vegetable-growing roof tiles.
The parts can be moved to the building site on one tanker truck, cutting down on costs (both environmental and monetary), says the original WSJ article about green housing ideas:
This method exists today, but it's not used very much, since homeowners associate prefabrication with lower-end homes. But the benefits for lowering energy use are substantial. The standardized construction in prefabricated homes reduces defects that can hamper energy conservation. And it's easier to ship prefabricated parts, which means reduced fuel use for deliveries.