Technical Updates

Posts Tagged ‘outside air infiltration’

Shortly after construction was completed, a seven-story, four-star hotel in Charleston, South Carolina, developed severe moisture and mold problems. The investigators attributed the problems to rainwater intrusion through the hotel’s exterior brick veneer. Following that diagnosis, the hotel owner spent more than $10 million on renovations, including a completely redesigned and reconstructed building envelope.

The summer after the renovations were completed, the moisture and mold problems returned. While focusing on the envelope leaks, the investigators had overlooked the significant secondary source of moisture: outside air infiltration.

In areas like South Carolina, where hot, humid conditions persist, IAQ problems are largely due to a combination of high ambient moisture, improper interaction between the building envelope and the HVAC system, and misapplication of design and operation principles.

1) High ambient moisture – Given the high ambient moisture levels in humid climates during the summer months and the dehumidification limitations of many AC systems, excessive moisture accumulation within buildings and the resulting microbial growth are understandably major problems. Microbial-related IAQ problems in buildings can also occur in temperate climates, although more serious errors in the design, construction, or operation of a building normally must occur for such problems to develop in these areas. Cold climates are just as susceptible to moisture problems as hot, humid climates, and building envelopes must be designed accordingly. Many microbial problems in temperate climates are more commonly a result of water intrusion (rainwater and subsurface water) through breaches in the building envelope system, including subsurface envelope systems.

In all climates, anything that elevates the indoor RH or results in damp materials (leaky pipes, for example) for an extended period can cause microbial IAQ problems. Landscape irrigation systems, indoor swimming pools, and building humidification systems can provide enough moisture to create microclimates and microbial growth problems, even in dry climates. Buildings in Boise, Idaho; Denver, Colorado; and Kona, Hawaii have all been hit with severe IAQ problems from microbial growth as a result of introduced moisture, despite the fact that they are considered arid climates.

To be continued…