The successful implementation of a new housing technology needs social acceptance which has to be tested by post-occupancy evaluations. In discussions about strengths and weaknesses of passive housing, possible overheating in summer is a main critical point. A field project supported by Wienerberger AG asked about user behavior and satisfaction in passive housing under summer conditions.Ten apartments in three passive housing estates of Salzburg City, Austria, were analyzed. Four apartments were part of Paradiesgarten, 5-floor low-energy brick buildings, three in Postareal, a concrete high-rise (8-floor) block, and three in Samer Moesl estate, a 3-floor wood construction. Participants received a diary form and were asked to evaluate three times per day their subjective living room temperature, humidity and air quality, and to record their sun shading and ventilation behavior without behavior briefings. Temperature/humidity loggers were installed in the living and sleeping rooms of every apartment. For every estate, an outside temperature logger profile was obtained. The survey period from August 1 to 18, 2011 included several days with maximum temperatures over 25° centigrade. Debriefings on optimum behavior were given at the end of the project.322 diary records were obtained from the ten apartments together with a parallel 3,812 hourly temperature/humidity logger record series for two rooms each. A correlation analysis of the three estates showed that about 90% of the diary records came from living rooms. Logger living room temperatures correlated significantly with the number of persons present, and with subjective air quality. Logger living room temperatures also correlated significantly with subjective temperature wishes (lower/OK/higher) at Paradiesgarten and Samer Moesl, but not at Postareal. Logger living room humidity did not correlate with subjective humidity wishes.Only at Paradiesgarten, measured living room air temperatures correlated significantly with shading behavior. Effective self-reported ventilation behavior (windows closed at daytime, open in cooler nighttime) correlated with living room air temperatures in all three estates.Problems with high living room temperatures were caused by open bottom-hinged sash windows at Paradiesgarten estate and by open balcony doors at Postareal estate. In 295 self-reported diary episodes, 69% recorded effective and 31% ineffective summer ventilation. As a result of the Salzburg field project, it is recommended to instruct occupants of passive housing how to shade and ventilate their apartments in hot summer periods to optimize performance of this building type and to reduce complaints.