Bob Prewett explains why Passivhaus is often too much for heritage buildings

Episide 30. Retrofit expert Bob Prewett describes how a client’s brief for an ‘extreme retrofit’ in 2008 gave him ‘something bigger than architecture to think about’. Divided between London and Wells, the ten-strong Prewett Bizley Architects has a portfolio of completed retrofit projects that achieve upwards of 70% energy savings and regularly monitors its buildings to understand how they operate over time. Although a founder member of the Passivhaus Trust, Bob observes that ‘we rarely push all the way to Passivhaus which is a bit strong for many heritage buildings’. Self-taught when retrofit resources, training and exemplar projects were scant, Bob explains the many ways architects can upskill today.