Special Maintenance Considerations - Effective Building Maintenance: Protection of Capital Assets - page 122

criterion is most appropriate, moldmildewcanusuallybeavoidedbylimiting
surfacemoistureconditionsover80%toshorttimeperiodsand70%forlonger
periods(eventhoughsomemoldswillbegintogrowatarelativehumidityas
lowas60% ). These criteria should only be relaxed for nonpo rous surfaces
that are regularly cleaned. Most molds grow at temperatures above ap-
proximately 40°F. Moisture accumulation below 40°F may not cause mold
and mildew if the material is allowed to dry below the critical moisture
content before the temperature rises above 40°F.
Potential substrates for mold growth include wood, paper, and tex-
tiles, which are common in buildings. Some molds will even grown on
substrates that provide no nutrients, such as steel or fiberglass, as long as
nutrients and water are present in the air or in dust settling on the molds.
Themostimportantriskfactorformoldgrowthindoorsisexcessliquid
waterinbuildingmaterialsduetowaterintrusionduringconstructionorwater
intrusionfromrainand/orwaterleaksafterthebuildingisoccupied.Inhot,
humidclimates(whichincludesmostofthesoutheastUnitedStates),thesecond
mostimportantriskfactorishighhumidity,eitherintheairorinthesubstrate
materialduetoiniltrationofhumidoutdoorairandexacerbatedbyimproperly
designedoroperatedHVACsystems.
The best way to prevent mold growth is to prevent moisture intru-
sion problems and this process starts with the roof.
Every facility must develop and implement an aggressive roof-
maintenance program as outlined in this text. This program would in-
clude periodic inspection of every roof to identify deficiencies. It is best
to perform these inspections in each spring and fall. Inspections should
be performed by individuals capable of determining not only apparent
immediate problems, but also conditions that could become problems in
the future. The inspections should concentrate on high-risk areas such
as around roof hatches, drains, mechanical equipment, and high-traffic
areas. As part of these inspections, also include roof flashings and drains,
plumbing vents, etc.
In addition to semi-annual inspections, perform inspections after
severe storms, repair or alterations to rooftop equipment, or re-roofing
projects in adjacent roof areas. Perform repairs in a timely manner; once
inspectors have identified deficiencies, a qualified roofing mechanic must
make the repairs immediately.
Aside from the roof, foundations and walls are often the source of
water intrusion problems. Groundwater can be kept out a building if the
surrounding grade properly slopes away from the wall and adequate site