I live in a hundred year-old house where most everything is original: the windows (drafty), the walls (uninsulated), the furnace (burns oil). I need only look at my heating bill every month to deduce what the Commission for Environmental Cooperation has determined through a two-year study—homes and office buildings in North America account for over one-third of the continent's greenhouse gas emissions. They are terribly inefficient.

The next time you close your eyes and imagine your house of the future, picture a bunch of soda bottles. That´s essentially what Philadelphia architects Stephen Kieran and James Timberlake have been working with in their quest to identify materials, technologies and mass-manufacturing techniques that they expect will reinvent their profession.