It is recognized that as humans age, their ability to withstand high or low temperatures reduces. Temperature extremes can also worsen chronic conditions, including cardiovascular, respiratory and other health issues. This study analyses 40 apartments in a single building in Auckland, New Zealand to determine whether the newly designed and constructed apartment, specifically for retirees, is delivering a suitable thermal interior environment during the warmest months of the year. Despite holding this green certification and meeting specific requirements to achieve cooling points that are meant to reduce the likelihood of overheating, the building exhibits significant signs of overheating in the two warmest months of the year (January and February) with two-thirds of apartments failing the CIBSE TM59 overheating criteria. The summertime performance of this green-rated building crucial insights for design professionals policymakers and developers of green building rating tools.