HA-2459 -- The Calculation of Air Infiltration Rates Caused by Wind and Stack Action for Tall Buildings PDF

The air that leaks through cracks and openings in a building envelope contributes to the heating and cooling loads of a building. Because its contribution to the total loads can be quite large, accurate estimates of infiltration rates are required for proper sizing of HVAC systems and analyzing the performance of various energy conservation measures. At present, methods for calculating infiltration rates are either over simplified with possible attendant large errors or very complicated involving the use of a computer model building.

A method for calculating the air infiltration rate caused by stack action was given in a previous ASHRAE paper! by the authors. For this paper, it was necessary to develop methods for calculating infiltration rates caused by wind action alone and in combination with stack action. A literature search for suitable wind pressures measurements for air infiltration calculations revealed that investigations of wind pressures on tall buildings have been directed almost exclusively to improving structural load calculations with measurements concentrated on those areas of the wall surfaces likely to be exposed to the greatest wind pressures. As air can leak through any part of exterior walls, detailed information on the distribution of wind pressures is required for infiltration calculation.

Recently, the National Aeronautical Establishment of the National Research Council of Canada (NRCC) conducted extensive pressure measurements on a tall building model in a boundary layer wind tunnel. Wind pressure data from this investigation were made available to the authors and, with the aid of a computer model building, procedures for calculating air infiltration rates were developed.