The built heritage of Wales and the wider UK is a multifunctional collection of structures, many of which have moved beyond their original purpose to a present in which they must perform for communities and collections on a local and national scale. Whether a renowned visitor attraction or a modest private home, historic buildings are environments in which the wellbeing of people and things are safeguarded. How effectively are they performing in this role? Set against a landscape of sky-high energy prices, ambitious net-zero carbon targets and rapidly evolving heating technologies, can heritage and conservation sciences guide owners, tenants and managers of historic buildings in their decision-making? Can we benefit from understanding traditional building methods and retrofit principles to improve lived experiences of housing today? In a changing climate, what leeway do we have to broaden our long-held acceptable environmental parameters for preservation of heritage artefact collections? Led by Cardiff University experts from the School of History, Archaeology and Religion and the Centre for Sustainable Building Conservation in the Welsh School of Architecture, PERFFORM puts built heritage under the microscope. Using heritage science to understand how buildings work, it examines the impact of their internal environments on human lifeways, past and present. It activates conservation science to correlate those environments with decay of buildings and collections to offer guidance for their preservation.