Solar thermal systems for sustainable buildings and climate change mitigation: Recycling, storage and avoided environmental impacts based on different electricity mixes

•Solar thermal systems for buildings: environmental life-cycle assessment and policy.•Materials with considerable impacts on human health/ecosystems have been identified.•By involving recycling, appreciable reduction in these impacts can be achieved.•During the phase of usage, solar thermal systems offer considerable avoided impacts.•The avoided impacts based on the electricity mixes of Spain and Italy are presented.