The traditional gabled roof that we are all familiar with was engineered to slough off snowfall. But in an uncertain post peak oil future of possible energy shortages and water shortages, more and more houses are showing up with roof-shapes engineered to harvest their own rainwater, and support solar power generation.

This creates a butterfly roof, the opposite of the traditional gable. The very post peak oil Kangaroo House in increasingly drought ridden Australia has the same distinctive roof shape, for the same reasons: it acts as a huge funnel for rainwater, which can then be harvested.

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