Pressure difference across windows in relation to wind velocity

States that it is usual to assume a certain pressure difference across a window for a given wind velocity. Describes method of recording and instrumentation used to record wind speed and direction and pressure difference across two windows. Gives results of measurements showing dependence of pressure on winddirection. Shows that stack effect, even in buildings of moderate height, may be of sufficient importance to require a different allotment of heating capacity between lower and upper floors.