Techniques to Estimate Commercial Building Infiltration Rates

The estimation of low-rise, residential building infiltration rates using envelope airtightness values from whole building fan pressurization tests has been the subject of much interest and research for several decades, constituting a major topic of discussion during the early years of the AIVC. A number of empirical and model-based methods were developed, with their predictive accuracy evaluated in field studies around the world. Infiltration estimation methods for residences are now commonly available in guidance documents and employed in whole building energy and indoor air quality modeling. However, the greater complexity of many commercial buildings, including their size, multizone airflow dynamics and the influence of mechanical ventilation systems, makes the estimation of infiltration rates from fan pressurization test results more challenging. As a result, progress on infiltration estimation methods for commercial buildings has been slower than in low-rise residential. This paper reviews methods for estimating commercial building infiltration rates going back to the 1970s. More recent approaches using correlations based on a large number of multizone airflow model simulations are presented as a more feasible approach. Particular attention is given to how energy models have dealt with infiltration estimation in commercial buildings, with a detailed discussion of how the energy analysis program EnergyPlus has considered infiltration. More complex and presumably more accurate methods of accounting for the energy impacts of infiltration in commercial buildings, based on coupled airflow and energy analysis models, are also discussed as they have become more accessible in recent years given the increasing power of personal computing.