IBSE TM40 | PERFORMANCE CRITERIA A rigorous exercise CIBSEs upcoming TM40 includes new performance criteria definitions for health and wellbeing. CIBSEs Julie Godefroy says designers should target specific outcomes and use health-based metrics to ensure everyone is speaking a common language T he past decade has seen signicant advances in our understanding of how environmental factors affect our health and wellbeing, and in design solutions in the built environment. Combined with worldwide trends such as increased life expectancies, ageing populations, pressures on healthcare systems and the growth in urban living, these developments have prompted a signicant revision of CIBSE guidance on health and wellbeing considerations in building services Technical Memorandum 40 (TM40) Health and Wellbeing. TM40 is now in the nal stages of production, and this article summarises one aspect: the approach for dening indoor environment criteria for health and comfort. The TM will also include guidance on design, construction and operation. For an overview of the revision, see CIBSE Journal March 2018 (bit.ly/CJJun19TM401). Regular updates are provided at the CIBSE Knowledge Portal (bit.ly/CJJun19TM40). Defining performance A signicant update in the TM is the focus on building performance outcomes for each environmental factor (light, humidity, thermal condition, and so on), the TM summarises existing health-based guidance and regulations, and proposes recommended levels accordingly. These levels may be used as targets for example in new buildings, t-outs and refurbishments or as benchmarks in existing buildings to dene priorities and short-to-longer-term improvement programmes. In some areas such as air quality, this is a 4 June 2019 www.cibsejournal.com CIBSE Jun19 pp04-06 TM40 Supp.indd 4 24/05/2019 13:36