For Phase II, the evaluated dorm rooms were located in 13 buildings. Four were built between 1940 and 1960, two between 1977 and 1983, three between 1993 and 1999, and four after 2000. For newly constructed dorm buildings, concrete structure and PVC frame windows were used instead of the brick-stone structure and the wooden frame windows used in older buildings. Ventilation for all dorm rooms consisted solely of opening doors and windows. The out-to indoor air flow rates for rooms measured during summer varied significantly, from 0.8 to 110 L/s per person, with a median of 18 L/s per person. Air flow rates measured in the heating season (from Dec. 5, 2006 to Apr. 14, 2007) varied from 0.3 to 24 L/s per person, with a median of 3.0 L/s per person. Ninety percent of the dorm rooms had an outto indoor air flow rate less than 8.3 L/s per person.