Resources are dwindling, prices are rising - and energy efficiency has never been more important. Commercial buildings have long been designed with conservation in mind - Taiwan's national stadium is covered almost entirely with solar panels, and the CaixaForum Museum in Madrid boasts a living wall of 15,000 plants.
However, with the world's population predicted to exceed 8 billion by 2050, architects are turning their green design skills to residential homes. Potential structures range from ancient mudbrick domes, to space-age Earthships.
Some designs are more viable than others. The Big Deal team have identified five of the most promising candidates - for a glimpse of the future, check out our infographic below.