It is often claimed that buildings certified as being sustainable secure high IEQ improving occupants' satisfaction and performance. There are few data that documenting this claim. Two multi-building, multi-country measuring campaigns were carried out to provide evidence on the performance of two certification schemes: Green Mark and DGNB-DK. Week long measurements of parameters describing thermal, atmospheric, acoustic and visual environment were performed, along with administration of a web-based occupant satisfaction survey and rating of their work performance. Three short cognitive games meaured short-term memory, concentration, and text comprehension. The results will be discussed comparing them to previously published data.