Many strategies to reduce climate change have large, immediate health benefits, while others may pose health risks or tradeoffs. Examined systematically, a powerful new dimension of measures to address climate change emerges.WHO's "Health in the Green Economy" series reviews the evidence about expected health impacts of climate change mitigation strategies for key economic sectors, both in terms of health co-benefits and risks. The series identifies how better design of housing, transport and energy policies could yield significant health co-benefits and help prevent a growing global burden of non-communicable diseases. Examined through this health lens, a powerful new dimension of evidence emerges to support more coherent win-win strategies for health, climate and sustainable development. Opportunities for potential health and environment synergies are identified in this first report for the housing sector.