Environmental Engineering Reference
In-Depth Information
cannot be supported by medical science. It would be more desirable to use
heated vaporizers if humidification is required to protect indoor materials
and increase humidity levels during the wintertime in cold climates.
It is not uncommon for building occupants to overhumidify their resi-
dences. Such overhumidification can result in the formation of condensate
on cold windows, with subsequent mold infestation on windowsills and
frames. Overhumidification should be avoided.
Dehumidification.
Elevated humidity is common in basements, even
when a building site is relatively dry. Basement environments are influenced
by the cool environmental conditions associated with the ground. Conse-
quently, relative humidities are often high. Relative humidity can be reduced
by heating basements to achieve acceptable humidity levels during winter
in northern climates and dehumidifying during summer. Dehumidification
units require a minimum temperature of approximately 65°F (18°C) to oper-
ate properly (to prevent coil freezing).
Water intrusion.
A common, but hidden, problem in brick veneer and
masonry-clad homes is penetration of rain water into building cavities
through the mortar, particularly during windy, rainy weather. Such cladding
should be constructed with weepholes that are open and functioning. If not,
it should be provided with functioning weepholes on a retrofit basis.
Rain penetration into building cavities can also occur through cracks
around windows and doors due to poor caulking practices and caulk failure.
Good maintenance requires that windows and doors be well caulked at all
times. It also requires that settling cracks in mortar be caulked early in their
development to prevent water intrusion and mold infestation.
Miscellaneous condensation.
Water condensation on poorly insulated
walls and ceilings during winter weather can be prevented by use of insu-
lation; mold growth in bathrooms due to high humidity can be avoided by
installation and use of bathroom exhaust fans; mold growth associated with
water spills in bathrooms and leaking plumbing can be avoided by quickly
(within 24 to 48 hours) drying the wet materials and, in the case of plumbing,
repairing leaks as soon as possible; borders around windows and door frames
need to be well caulked at all times and routinely inspected and attended to;
and all water leaks associated with roofs and other damaged materials need
to be quickly repaired and all materials dried within 24 to 48 hours.
. Though nonresidential buildings
experience mold infestation problems, they are usually somewhat different
in their origin. Common causes of mold problems include roof leaks, plumb-
ing failures, leaks from AHUs, improper operation of HVAC systems, and
infestation of filters and duct liner materials.
Roofing leaks.
Leaks are common on flat-roofed buildings. Significant
maintenance attention and sealing roof surfaces are necessary to prevent
water intrusion. Once leaks develop, they must be repaired quickly, and
wetted materials dried, to prevent infestation.
Plumbing failures.
Plumbing failures may include leaks at joints or sink
fixtures, overflowing toilets, pipe breaks, sewage backups, etc. The key to
Problems in nonresidential buildings
