Naturally ventilated buildings have a key role to play mitigating climate change. The predicted indoor temperatures in spaces with simple single-sided natural ventilation (SNV) are compared with those in spaces conditioned using a form of edge in, edge out advanced natural ventilation (ANV) for various UK locations. A criterion, for use in conjunction with the BSEN15251 adaptive thermal comfort method, is proposed for determining when the risk of overheating, both now and in the future, might be deemed unacceptable. The work is presented in the context building new, and refurbishing existing, healthcare buildings and in Particular hospital wards. The spaces conditioned using the ANV strategy were much more resilient to increases ill both internal heat gains and climatic warming than spaces with SNV. The ANV strategy used less energy, and emitted less CO2 than conventional, mechanically ventilated (MV) alternatives. In a warming world, the 'life-expectancy' of passively cooled buildings can be Substantially influenced by the internal heat gains. Therefore, resilience to climate change, susceptibility to internal heat gains and the impact of future heat waves, should be an integral part of any new building or building refurbishment design process. (C) 2009 Elsevier B.V. All rights reserved.