The indoor environment is an increasingly studied habitat for microorgan- isms, particularly fungi and bacteria. However, microbiology of the built environment (MBE) studies tend to be located in one discrete region, and often in one specific locality. While these individual studies have helped to elucidate some of the important ecological drivers of the built environment microbiome, taken together they suggest that different processes may structure communities depending on, for example, the target organism, building type and operation, or climate. We propose a NESCent working group to undertake a composite analysis of publicly available microbial datasets from a range of built environments.