commercial side of the codes is mis- guided because the taller a building is, the greater the pressures exerted on it by wind and stack effect, and the great- er the potential for air fl ow. The amount of air leakage through a building shell will be defi ned by the cumulative size of the holes in the shell and the difference in air pressures from one side of the air barrier to the other. In other words, for a hole of any given size in an air barrier, if there is no pressure difference from one side of the hole to the other, air won’t fl ow, no matter how big the hole. Conversely, if the pressure differential is increased, then, given the same-size hole, air fl ow will increase. In addition to naturally occurring pressures, like wind and stack effect, mechanical equipment typically pressurizes tall buildings for fi re-safety purposes, leading to even greater pressure differentials and thus greater air leakage for a given-size hole. Currently, only certain “stretch
codes,” a term generally applied to vol- untary or “beyond the norm” codes, re- quire commercial building-shell testing. For instance, the International Green Construction Code has a provision for air-infi ltration testing. The Washington- based U.S. Department of Defense has a requirement that its new construction and major renovation projects undergo air-leakage testing under an “Army Corps of Engineers Standard.” This standard is by far the most progressive in the country, and the DoD remains proactive in requiring tighter build- ings. Washington state also requires air infi ltration testing for all new buildings and major rehabs. One of the reasons for the discon-
nect between residential and com- mercial air-infi ltration testing seems to stem from a lack of information in the marketplace and industry regarding the relative ease with which commercial tests can be conducted. In the not-too- distant past, buildings would have been tested with large trailer-mounted en- gine-driven fans. This was in contrast to the hand-carried fan (commonly called a blower door) used in residential test-
of the codes is misguided because the taller a building is, the greater the pressures exerted on it by wind and stack effect, and the greater the potential for air fl ow.
ing. The perception in the marketplace is that commercial testing is complex, intrusive, expensive and unwieldy. How- ever, fan technology and software have advanced dramatically. The days of the trailer-mounted fans are all but over. Advanced computer control software and fan technology allow for any num- ber of smaller hand-carried fans to be connected together, allowing relatively easy testing on buildings of almost any size. Six or seven of these hand-carried fans have about the same capacity as one of the old trailer-mounted blowers.
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As commercial building codes
continue to evolve, we will see more attention placed on the deleterious ef- fects of air infi ltration on our buildings. Tighter building envelope design will most assuredly become one of the next green-building best practices that be- comes commonplace for architects and engineers. As building owners become aware of the benefi ts of reduced air in- fi ltration, including energy savings and more productive work environments, the current indifference to air infi ltra- tion will rapidly become history.
Not addressing air infi ltration in the commercial side
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