Wind tunnel tests are conducted with a 1/50 scale model of a low-rise detached house. Models of detached house are arranged uniformly with various density(building coverage). The model concerned is located at the midst of the arrangement. Coefficients of surface wind pressure on the roof and the walls of the model house concerned are measured under this condition. The inside pressure and the air change rate of the house are evaluated by numerical method on the basic of measured wind pressure coefficients, assuming a uniform distribution of leakage areas. Findings are given as follows. 1. When the model house is surrounded by similar buildings, both of infiltration and exfiltration are observed on the walls and the roof. 2. The air change rate of the model house with the arrangement of 40% building coverage is about a half of that of the single model with no surroundings. 3. Air change rate is 0.8 times per hour under the following conditions: (1) the house is one story with gable roof, (2) grade of air tightness is 5(αA = 12.5cm^3/m^3), (3) standard wind velocity is 4m/s, (4) building coverage is 20%. 4. When wind velocity exceeds 3m/s, air change rate is greatly affected by the characteristics of leakage.
