The 26th international conference on Passive and Low Energy Architecture (PLEA 2009) explores our quest for passive and low energy architecture through the occupants’ perspective at the urban and building scales. In the current context of major technological shifts in the fields of alternative materials and energy, the aim of the conference is to position the inhabitants as a key ‘active’ determinant of energy performance in ‘passive’ design through adaptive opportunities. Some 171 scientific papers selected by our Technical Committee amongst more than 500 extended abstract submissions present the most recent thoughts and researches within the rapidly evolving world of low energy architecture and occupants’ behavior. These proceedings are structured into three main chapters: Challenges: Occupants-Communities-Education; Strategies: Daylighting-PassiveHeating/Cooling-Post Occupancy Evaluation; and Integration: Integrated Design Process-Certification Tools-Innovative Materials and Systems. A companion CD includes all oral and poster papers.