The landmark Breathing Buildings Houghton-le-Spring Primary Care Centre is profiled in the August 2015 edition of the CIBSE Journal. (http://portfolio.cpl.co.uk/CIBSE/201508/natural-ventilation/) The article describes how the building is performing and reveals the robustness of the scheme. In winter the building performs like all Breathing Buildings, with mixing ventilation used to temper the incoming cold air. In summer the building uses a thermal wall to aid the cooling of the space on hot days. The extensive data now collected shows that the natural flow during a summer night is the reverse of the daytime flow, but that there are additional benefits in using fan-driven night-cooling in order to ensure the coldest air is in direct contact with the thermal mass. The article also describes the CO2 data collected during a summer day and explains for the first time why the CO2 levels can be higher near the entrance ways than in the depth of the interior – read the article to find out why!