This paper presents a study in support of decision mak-ing for building retrofit and energy supply strategy at the Royal Botanic Gardens, Kew in southwest Lon-don, England. The study considers the issues that af-fect simulation at the building scale specific to this site, in particular simulation of heat flow in botanical glasshouses, retrofit of heritage structures and simula-tion of power load for buildings with high equipment density. In addition, the study considers the potential benefits to be gained from energy microgeneration and supply at the district scale, investigating supply opti-misation for a cluster of buildings within the Kew site.