Building problems can cause degraded air quality in all phases of a building's lifecycle: design, operation, and maintenance. The purpose of this article is to examine common design characteristics that may be problematic to the achievement of acceptable IAQ and that are generally easily identified and are usually avoidable.
A not-so-uncommon problem is an oversized air conditioning system. The oversized system could be due to a design error or seasonally reduced occupancy/thermal loads such as often occurs in schools in summertime. The oversized system causes rapid response to high temperatures. However, because of oversizing, hot, humid air brought into the system is not adequately dehumidified, producing increased relative humidity (rh) in the space. Sustained rh above 60% increases the likelihood of microbiological growth on environmental surfaces. The air-handling system can serve as a distribution conduit for microbes throughout the zone.