Environmental Engineering Reference
In-Depth Information
of appropriate building sites, provision of adequate site drainage, and atten-
tion to good building maintenance. Once a building (or some portion thereof)
becomes infested, the problem may be mitigated easily or only with great
difficulty. The prevention and mitigation of mold infestation problems
require an understanding of factors that contribute to mold growth. These
are described in detail in Chapter 6.
i. Avoidance. Moisture, both in the liquid and vapor phase, is a key
factor in causing mold infestation problems. As indicated in Chapter 6, many
species require a minimum R.H. of 70% for spore germination but can grow
at lower R.H. Avoidance of mold infestation problems requires that buildings
and materials be kept relatively dry.
ii. Building sites. Many mold infestation problems, particularly in
residences, are associated with building sites that are poorly drained. Such
sites are typically characterized by heavy clay soils and persistent or seasonal
high water tables. Moisture problems on wet sites may be exacerbated by
trees that produce heavy shade. Individuals and occupants who have a
history of allergy or asthma should avoid living on a poorly drained site.
Sites can be evaluated for drainage hazards using soil maps, or by profes-
sional soil scientists. Many existing homes on poorly drained sites (depend-
ing on their age) have developed mold infestation problems. These may be
identified from a casual building inspection (e.g., strong mold odor) or a
more rigorous professional inspection.
iii. Building management. Mold infestation in many buildings occurs
as a result of poor management (and sometimes construction) of the building
and its environment. This is true for both residential and nonresidential
buildings. In both instances, mold infestation problems are often a result of
neglect or various occupant behaviors.
. Mold problems in residences not associ-
ated with poor building sites include infested cool mist humidifiers; overuse
of humidification systems; lack of dehumidification in basements; use of low
nighttime and seasonal setback temperatures; poorly constructed brick or
stone veneer; inadequate wall and ceiling insulation; poorly ventilated bath-
rooms; inattention to water spills and plumbing leaks; inadequate caulking
of windows and doors; and a less than expeditious response when cleaning
up, drying, and repairing materials associated with water intrusion through
the building envelope.
Humidifiers and humidification.
Use of cool mist humidifiers in a resi-
dential environment can result in significant localized mold exposure from
contaminated reservoir water. Such contamination results when humidifiers
are not cleaned routinely. Studies have shown that cool mist humidifiers
require regular cleaning to maintain low microbial levels. Because of the
significant cleaning that is often required, it is better not to use cool mist
humidifiers. Use of humidification based on recommendations of allergists
Problems in residential buildings
