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What
is a Uniform Building Code and what does it have to do with mold?
During the last century, building standards were developed to assist
builders and architects to design and build structures that met the
needs of those who used them. One major flaw which developed during
this period was the idea that you could apply a single building standard
to a wide area of the United States. This code eventually came to be
most commonly known as the Uniform Building Code. There are several
variations of building codes and some of them were developed to provide
information relevant to specific areas of the country. The one we are
most familiar with is called the Southern Building Code.
During the recent past, new materials came on the market that contained
synthetic materials and bonding agents which continued to release gasses
such as formaldehyde into the living space long after they were installed.
As far as we know this alone did not cause many problems until the energy
crunch of the 1970's caused the building industry to "tighten the
envelope". Replacing single layered windows with double and triple
glazed windows, adding caulking, insulation and interior wrapping of
the exterior walls with polyethylene vapor barriers as well as other
features intended to completely seal the interior of the house from
the exterior air caused the problem of "off gassing" to be
exaggerated thereby causing health problems for the occupants.
The first solution to this problem was a modification of our air conditioning
system which called for an increase in air exchange rates. In other
words, we increased the air flow rate of the system in an attempt to
"dilute" the air by exchanging it more often. The problem
remains that there less fresh air being introduced because we have already
sealed out the outside air.
Initially this "tightening of the envelope" had little effect
on the proliferation of mold growth because moisture was not being introduced
from the outside. Yes, there was moisture being introduced on the inside
in the form of water vapor condensing on the interior walls of our bathrooms,
but so long as these rooms were properly ventilated with exhaust fans
or windows these mold problems were minimized.
Where does mold come from and why now?
As these homes that were build to be air tight started reaching ages
of 20 years to 30 years and developing problems common to their age
such as leaks in the roof or in the plumbing. Such leaks in flashing
around a chimney or a plumbing line that has a "pinhole" leak
can remain undetected for a period of time.
The flashing leak may be periodic since it only leaks when it rains,
but when it does leak, the water soaks into the masonry chimney and
remains within the brick for several days or more. Essentially, this
water "outgasses' from the brick in the form of water vapor over
a long period. Water vapor is not harmful by itself, but since the remainder
of the house is still relatively air tight, the "outgassed"
moisture has no place to go. If the air humidity and air temperature
remain at appropriate levels, mold spores will come to life and start
a colony.
Buildings need to breath just like everything else. Our clothes breath,
our cars breath, our closets need to breath and so do our houses. Grandma's
house may have breathed a little too much but since it was not air-conditioned
it had to be more open. Later when we decided that we needed tighter
houses to save money on energy costs for air-conditioning we ran into
a conflict of interest with mold spores.
What does this all have to do with building codes and why do we different
codes for different areas of the country?
The simple answer has to do with where is the warm humid air located
and where does it want to go and how can a building envelope determine
where is goes. In the South, our warm humid air is located outside so
it stands to reason that we want to keep it there especially if our
air conditioned house contains cool dry air. So what happens if it gets
in and cannot get out?
The biggest mistake of all came when building codes allowed for the
installation of polyethylene vapor barriers to be placed on the INSIDE
of the exterior walls. While this may be acceptable in Northern climates
it is a problem for homes built in the southern regions. The result
for us is that all of the humidity that is introduced into the inside
of the house cannot escape to the outside. Should our a/c system fail
to evacuate enough of this humidity (which is what helps to make the
air cooler), then we have a continuous build up of moisture. We cannot
blame the entire problem on the building codes however, because the
second factor in the problem is caused by how the occupants use the
system.
Is it the buildings fault or is it the users fault?
Condensation is the natural by-product when the warm humid air meets
the cool dry air. Simply stated, we now have water accumulating on the
inside of our house. So long as the a/c system remains working we may
still not have a problem but if we turn the system off every day while
we are gone in an attempt to save money we continuously allow the room
temperature and humidity levels to meet the demands of mold spores to
grow. We allow the moisture from our morning shower to remain in the
house when we turn off the a/c during the day. The temperature rises
until the relative humidity reaches the right conditions are present
for mold to grow. This is what mold is for, it lives and thrives on
these conditions and is natures way of balancing the air. The more mold,
the more mold spores are present when we get back home
There are many other ways that moisture can be introduced into the interior
space such as when we have our air conditioner humming away at a nice
72 degrees and a relative humidity of 40% and the kids open and close
the door 500 times every day. We let the moisture in but it cannot get
out unless the a/c system takes it out. Allowing the condensation drain
line to get plugged up is an invitation for mold to accumulate in or
near the a/c evaporator coil. When the system is turned off long enough
and the conditions are right, mold will grow on the coils themselves,
then when we turn it back on we circulate the spores throughout the
house.
Add this to the pot of boiling water on the stove, add a few hot showers
and mist the house plants daily and we now have perfect conditions for
condensation which occurs wherever it can. A good place for condensation
is in the cool cracks and crevices located all around the house. This
helps to explain why the mold may grow in an entirely different place
than where the water has penetrated the house. The mold is not growing
in the obvious place near the doorway but in the far back bedroom closet
where it is rarely open or noticed. Here it can grow undisturbed. A
nice comfortable dark cool climate with plenty of moisture. Sooner or
later, the spores grow and become airborne and eventually find their
way into the air ducts where they are continuously distributed throughout
the house.
It is therefore a combination effect caused by many factors including
the way the house was built and the way the house is used. All of these
factors must be examined before determining a solution should mold be
found to be a problem.
Why should the vapor barrier be on the OUTSIDE of the exterior wall?
One good reason to use a vapor barrier in hot and humid climates is
when brick is installed on the outside of the exterior wall. Brick soaks
up water like a sponge and releases the stored water as water vapor
over a period of several days and even weeks. This is fine so long as
this release of moisture stays on the outside of the house, but bad
news if it should reach the inside of the wall cavity. It is therefore
important to make sure that this moisture does not penetrate into the
wall stud area where it can collect and condense on these cooler surfaces.
I have a mold problem, what do I do now?
Find the source of the problem and make appropriate changes to the house
and/or to the way the house is used.
If the mold cannot be cleaned it must be physically removed. This needs
to be done professionally in a way that does not spread the mold spores
any more than they already are. Once the moldy materials have been removed
everything should be cleaned again.
Verify that the original cause has been repaired and change the use
patterns of the occupants to prevent reoccurrence of the original conditions
that gave the mold a place to grow in the first place.
There are no 100% guaranteed solutions and each house is different.
Each has different construction methods, different orientations, different
ways of aging and different lifestyles of the occupants. It is simply
not a very good approach to try to attack any single problem with any
single solution. It is a balancing act between having a house that can
breath but not breath so much we are uncomfortable. Water, moisture
and water vapor as well as temperature fluctuations will always be present
and will change from season to season and we must be aware of them.
Mechanical solutions are often recommended, but it is rare that just
a new air conditioning system or a dehumidifier will completely resolve
everything so be wary of simple solutions that do not take into account
the complete picture.
What should I watch for?
Some of the worst offenders in poor interior air quality are water intrusion,
air leaks, poorly designed or installed heating and cooling systems,
troublesome architectural design features, the use of high emission
building materials, improper storage of chemicals and failure to allow
for proper evacuation of warm humid air. But the most common problem
in hot-humid climates found in the Southern regions is putting the vapor
barriers on the wrong side of the wall and ceiling.
The second factor is closing up the house without ventilation while
a moisture source is active inside the house. For instance, you should
not shampoo the carpet then close up the house and leave for a week.
What are molds, dust mites and mildew?
Molds, mildew, fungi, bacteria and dust mites are biological pollutants.
Mold grows on organic materials such as paper, textiles, grease, dirt
and soap scum. Mold spores float throughout the house, forming new colonies
where they land when they have the right conditions. If they do not
have the right conditions for growth, they lay dormant for many months
or even years.
They are a natural part of our environment and are not harmful in normal
numbers. Mold, mildew, fungi, and bacteria are often found in areas
of the home that have high humidity levels, such as bathrooms, kitchens,
laundry rooms or basements. Dust mites thrive on dead human skin cells
and in bedding, carpeting and upholstery. When these areas are disturbed
during vacuuming, making beds or walking on carpet, the dust particles
become airborne. The same is true of animal dander.
What are the health effects?
Biological pollutants can cause allergic reactions. Symptoms often include
watery eyes, runny nose and sneezing, nasal congestion, itching, coughing,
wheezing and difficulty breathing, headache, dizziness and fatigue.
Dust mites have been identified as the single most important trigger
for asthma attacks.
How can I guard against biological Pollutants?
Prevent mold growth by keeping basements, bathrooms and other rooms
clean and dry. Use a disinfectant to clean surfaces that have mold on
them. Humidifiers, dehumidifiers and air conditioning condensing units
should be regularly cleaned with a disinfectant such as chlorine bleach.
Keep humidity at acceptable levels (less than 50%) and make sure there's
ample ventilation, particularly in areas where moisture builds up. If
you are sensitive to dust mites, consider replacing carpeting with hard-surfaced
flooring and use area rugs that can be removed and cleaned.
Vacuums with high efficiency filters or central vacuum systems can help
reduce the airborne dust generated by vacuuming.
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