The paper evaluates the carbon viability of office-to-residential retrofits. It aims to determine at what point in time a retrofit becomes more carbon-intensive than a theoretical newbuild scenario (with a similar design in the same location), primarily due to enhanced operational performance of the latter. Comparative Life cycle Assessments (LCAs) showed that despite the high embodied carbon savings of the retrofit, the newbuild scenario has a lesser carbon impact overall when considering a typical lifespan of 60–100 years. This was due to the newbuild outperforming the retrofit with regards to lower operational carbon emissions, annulling the initial embodied carbon advantage after 22 years. Considering that LCA is typically conducted for 60–80 years, and that on average a buildings’ lifespan in the UK is 60–100 years, it can be concluded that the retrofit would present a significantly higher carbon footprint over the entire life cycle, when compared to demolition and reconstruction. To address this, the paper also presents recommendations for minimal energy standards for retrofits, which aims to result in significant carbon savings.<p></p>