It has been necessary to check air leakage in dwellings due to complaints about thermal comfort and ever-increasing heating expenses. Airtightness of 18 rooms and air infiltration rate's of 34 rooms were measured using two blower doors and decaying tracer gas technique with nitrous oxide (N²O). Due to their availability, Canadian and ASTM standards were used for measurement. One of the blower doors was designed and constructed in Turkey. The test rooms were selected from new, unoccupied multistory apartment buildings and two-or three-story dwellings. Airtightness of the rooms was about 2.64 to 20.54 air changes per hour (ACH) at 50 Pa indoor-outdoor air pressure difference, while air infiltration rates were in the range of 0.16 to 1.99 ACH. To compare this with test results obtained abroad and with Turkish standards, normalized air leakage areas and air permeabilities of windows were also calculated from the results of airtightness experiments. They were found to be in the range of 0.57 to 24.45 cm²/m² and 1.7 to 4.5 dm³/(s.m), respectively, at 10 Pa indoor-outdoor air pressure difference.