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Serving NE Ohio Since 1956 |
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Mold and
Mildew Effective Attic
Ventilation: Just What the Doctor Ordered One the hottest
topics in the construction industry and elsewhere
is the adverse effect that exposure to mold and
mildew can have on human health. It has recently
been reported that the mold count inside a building
can be two to five times higher than
outdoors. The key to protecting
the health of residents is to minimize the
occurrence of mold and mildew from the start. One
important prevention method lies squarely with the
roofing contractor: the proper installation of
appropriate attic ventilation. Sick Building
Syndrome There have been
reports of cases in which exposure to mold and
mildew has led to violent bronchial attacks,
chronic sinus infections, central nervous system
problems and even memory loss. According to
cec-consultants.com, the Web site of an industrial
engineering consulting firm, biological
contaminants also have been linked to Sick Building
Syndrome. Building occupants in a "sick building"
may develop health conditions that appear to be
linked to time spent in the building. Research
indicates that symptoms disappear when the person
leaves the building. Although no specific cause of
symptoms has been identified, mold and mildew have
been named as one possible factor. The challenge for
contractors is that buildings typically possess all
elements necessary for mold growth: mold spores, a
sufficient nutrient base, a temperature of 40 to
100 degrees F and the presence of
moisture. Attic
Ventilation An effective attic
ventilation system can prevent moisture and control
humidity, thereby minimizing mold and mildew
growth. Inadequate ventilation is the cause of
about 50 percent of indoor air pollution and may
also cause shingles to deteriorate twice as fast.
Shingles installed with improper ventilation may
result in voiding the manufacturer's
warranties. An attic can easily
reach temperatures of 150 to 160 degrees F. Cooling
requirements for the home are raised dramatically
in warmer months. The rate of moisture condensation
increases when warm, moist air is trapped in the
attic and comes in contact with cool air and
building materials in colder weather. An article by B.R.
Stewart, "Attic Ventilation for Homes," which he
published as an agricultural engineer,
environmental control, at the Agricultural
Extension service of Texas A&M University,
further explains. "Ventilation of the home attic is
important for two reasons," he says. "During the
summer, excess heat that builds up in the attic
during the day results in high-energy costs for
cooling. Also, moisture produced within the home
may move into the attic if ceiling vapor barriers
are not used. If this moisture is not exhausted
from the attic, it can condense and cause
insulation and construction materials to
deteriorate. Thus, temperature and moisture control
are the major reasons for providing attic
ventilation." Though today's homes
are sealed more effectively from weather intrusion,
moisture will still enter the home no matter how
tightly sealed. A typical family can generate 2 to
4 gallons of moisture per day through routine
activities such as cooking, bathing and laundry.
Other daily moisture causes in the home can include
flooding, leaking pipes, damp basements, and/or
leaky roofs. But moisture can also
be present in buildings in its gaseous state,
commonly referred to as humidity. At a 70-percent
humidity level, the growth of fungi is rapid.
Unfortunately, relative humidity often exceeds 70
percent indoors even when attic ventilation
requirements are met. This problem is prevalent in
humid climates where the outdoor relative humidity
value commonly exceeds 70 percent. By controlling
the indoor relative humidity between 30 and 50
percent, biological growth can be
minimized. What to
Do The question then
becomes "What is the best way to ventilate the
attic?" There simply is not one way that is "the
best" but contractors must consider which type of
ventilation will work in their individual
circumstances. There are two types of ventilation:
dynamic and static. Power, or dynamic,
ventilation is accomplished in two ways. According
to Stewart, in homes not mechanically cooled
(air-conditioned) the temperature can be controlled
to some extent by the use of attic fans. These fans
are usually ceiling mounted in a central hallway so
that outside air is pulled through open windows and
exhausted through the attic. Sufficient outlets
should be installed through the attic uniformly.
Again it is important to calculate the required
amount and position of vents to adequately
ventilate the attic. Keep in mind,
however, that power ventilation methods can add to
the energy use of the home. And according to
askthebuilder.com, "It turns out that rooftop- and
sidewall-mounted attic fans can actually suck air
conditioned air from your house into your attic
space." Another option is
static ventilation, which is the use of non-powered
ventilation products that work with the natural
flow of warm air and wind movement around the home.
This method takes advantage of two principles.
First, as air is heated it becomes less dense and
rises. Second, wind movement over and around a home
creates areas of high and low pressure. If a space
has high air outlets (exhaust) in conjunction with
low inlets (intake), ventilation occurs as the air
within the space is heated. Continuous ridge
ventilation combined with soffit vents is the most
common form of static ventilation. It provides for
a total movement of air throughout the attic space.
Other forms of static systems include gable vents
installed at the attic wall, and turbine vents and
pot vents installed near the peak of the roof that
work by drawing air from the attic
space. |
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