| Since the 1973 embargo by the oil producing and exporting countries (OPEC), this nation has been aware of the need to save energy. While many sectors of the economy, notably transportation, have been critically studied, unitl recently, one of the largest sectors--the buildings sector--has been virtually neglected. In the last few years, researchers have recognized that infiltration (the flow of air through leaks in the building envelope) is a critical factor in energy loss in buildings and merits concentrated research effort if national energy conservation goals are to be served. We know, for example, that the energy loss due to infiltration is between 6% and 9% of the total energy budget for the nation.;Our model, based on the determination of the "effective leakage area", was used to predict the infiltration at 15 separate sites. Pressurization was used to calculate leakage area which, in turn, was used to calculate infiltration. Findings were then compared to direct measurements of infiltration at these sites. Agreement between the model and direct measurement by tracer gas techniques was (+OR-)20% overall--a degree of accuracy far surpassing any previous model of infiltration capable of being generally applied.;This model can be used in large programs that model building performance, or it can be used by the policymaker who wishes to estimate the effect that certain regulations concerning leakage or leakage retrofits might have on infiltration. In this way, a simple leakage measurement (or estimation) replaces the costlier and more complex direct infiltration measurement as the experimentally measured quantity. We also discuss the limitations of the model and indicate directions for future research in this area.;*The work described in this report was funded by the Office of Buildings and Community Systems, Assistant Secretary for Conservation and Solar Applications of the U.S. Department of Energy under contract No. W-7405-Eng-48.;In this work we develop and validate a physical model of infiltration in buildings that can be used to predict the infiltration for a wide range of construction types and climate regions. To that end, the problems associated with commonly-user tracer gas methods for measuring infiltration were examined in detail so that results obtained from the model could be properly compared with actual measurements. In addition, a simple model of the hydrodynamics of typical leaks in the building envelope was devised to study the physical processes of infiltration (i.e. the flow of air through cracks in the structure of the building). Finally, a method for quantifying the leakage of the building envelope (the quantity analogous to envelope thermal conductance) was developed. The name given to this measurement technique is "AC pressurization". Although other methods exist for measuring the leakage of a building envelope, AC pressurization is far more accurate and can be used at lower pressures than any existing methods. |
