Universally recognised as emblems of many cities, historic buildings account for a quarter of Europe’s existing construction. Retrofitting such buildings presents many opportunities for reducing carbon emissions but can also present many challenges for preserving historic and aesthetic traits. Given the unique character of each building, standard energy saving measures are often not viable. SBE21 Heritage aims at fostering multidisciplinary dialogues and finding new affordable and efficient retrofit approaches to save our common heritage and guarantee a sustainable future.