Minimizing The Miseries Of Mold And Mildew:
You might smell a musty odor when you walk into
your house or maybe just when you go into the
basement. You might sneeze, you might not
Maybe you're allergic to mildew or mold spores,
and maybe you're not but chances are you really
don't know. While some medical experts say that
about 30 percent of the general population may
be allergic to mold and/or mildew. they note
that most in that group people who are only
mildly allergic probably ignore the symptoms.
Whether or not you are allergic mildly or
otherwise it's easy to keep minor mold and
mildew under control. So for your own comfort,
perhaps, and for the convenience of potentially
allergic guests, here's what you should know.
Spores and Dampness:
Think of mildew and mold spores as microscopic
seedlings floating in the air. They are
everywhere in trace concentrations; the problems
start when the concentrations increase. When
airborne spores make contract with damp or moist
surfaces, they multiply rapidly.
While you can't eliminate the spores, you can do
a lot, with proper ventilation and humidity
control, to eliminate their breeding grounds and
lower their concentration.
Humidity refers to moisture in air, the higher
the air temperature, the more moisture air can
hold. The amount of moisture the air is actually
holding relative to what it is able to hold is
called relative humidity. If air at any given
temperature is holding all the moisture it can,
the relative humidity is said to be 100
percent.
Walls:
When an air mass at 100 percent relative
humidity encounters a colder surface a glass
filled with iced tea, for example some of the
air will cool. Since the cooled air can hold
less moisture than it could when it was warm,
some of the moisture from the air will condense,
probably on the outside of the glass.
The same effect takes place when warm air comes
in contact with cooler walls something that
happens in various seasons at various times of
the day on the inside and outside of all
buildings. Inside it often occurs when heated
air comes into contact with cool interior walls
especially in un-insulated basements (finished
or unfinished). Outside this can happen when the
air meets the shady part of the house in the
evening, when the air itself is cooling and
beginning to lose some of its moisture;
encountering a cooler surface accelerates the
condensation. In both cases, airborne spores are
deposited on the damp surface and rapidly
multiply.
NOTE:
Operating dehumidifiers in basements is a good
idea in the summer. Spreading chlorinate lime
crystals over a concrete floor can absorb
moisture and kill mildew as well.
Sometimes mildew will form on a foundation wall
behind a finished wall. If there is a return
grill in the basement it can cause a negative
pressure on the basement area and pull mildew
spores into the living space air. Special
chemical fogging can sometimes to accomplished
to kill the mildew behind the walls. This is a
job for a professional.
Crawl spaces:
Homes with crawl spaces rather than full
basements often suffer from very damp conditions
frequently unobserved for years. The problem
here is a basic one, usually caused by water
seepage due to poor landscape drainage and
leaking pipes, resulting in a closed area with
high humidity and lots of mildew and mold. To
make matters worse, the humid air tends to rise,
carrying spores into the spaces above.
Heating and cooling systems:
Forced-air heating systems work by recycling
household air over hot metal. Simultaneously,
they can raise the spore concentration
throughout the house in several ways.
Forced-air systems often are fitted with
humidifiers designed to add moisture for
increased comfort during the winter. Many
humidifiers operate by passing a sponge or metal
discs through troughs of water that are almost
always spore generators.
Forced-air systems also may be fitted with air
conditioning coils above the furnace. The coils
"perspire" and drip moisture into a drain. If
the system is poorly filtered, dust can collect
on the wet coils and provide a perfect
environment for spore growth.
Some forced-air systems in houses built on slabs
have ducts laid under the slabs. These ducts are
good spore breeding grounds because humid summer
air can enter and condense on the cooled
interiors. In addition, poor drainage around a
house often will allow some water to seep into
the ducts. Return ducts through damp crawl
spaces act like vacuum cleaners sucking up
spores.
SPECIAL NOTE:
Some rarely used forced air systems actually
utilized sealed crawlspaces for delivery of the
air. Air was pressured into the space and then
exited via grills cut into the flooring system.
No ducting was utilized. This type of system is
highly likely to contribute to mildew and radon
problems.
Closets:
Closets on outside walls often have mildew or
mold growing in them because there isn't enough
air movement to ventilate the space properly.
Attics:
Moisture tends to rise in houses, and if the
attic is insufficiently ventilated it can
condense on the cold underside of the roof.
REMEDIAL ACTIONS:
Basement walls should be insulated with a
plastic vapor barrier stretched against the
foundation.
Dehumidifiers should be run in the summer with
the windows closed.
Clothes dryers should be vented to the outside
of the house.
Steamy bathrooms can be fitted with exhaust
fans.
Mildew on walls can be sponged with a solution
made from I quart of chlorine bleach, 1 gallon
of water, 1/3 cup liquid household detergent and
1/3 cup of tri-sodium phosphate. This solution
may bleach out some colors, so try it first on a
small, inconspicuous spot. (Because chlorine and
ammonia give off a poisonous gas when they are
combined, be sure the household detergent does
not contain ammonia. Never mix chlorine and
ammonia.)
Crawl spaces should be kept dry. Make certain
the grading against the foundation works to keep
water away. Stretch a 6mil polyethylene
(plastic) vapor barrier over any dirt. Vents
through the foundation walls should be left
open.
Fungicides can be applied to mildewed or molding
flooring.
Furnaces should be kept very clean (include the
inside coil in your air conditioning maintenance
contract); ducts that run through crawl spaces
should be sealed and insulated; and trough-type
humidifiers should be avoided.
Closets should not be stuffed with clothing.
Allow space for air circulation and consider
installing a vent in the door.
Never close attic vents for the winter and make
sure they are not blocked by siding.
If bath or kitchen exhaust vents open into the
attic, extend those ducts directly to outside
vents. Problem attics can be fitted with
additional vents.
Caveat Emptor:
When buying a house, persons with known
allergies to mold and mildew should avoid those
with basements or crawl spaces; if that is not
possible, they should be certain that these
spaces are bone dry. Also, avoid houses with
slab duct systems and houses that are heavily
shaded and surrounded by trees.
CAUTION:
This primer is an over simplification to assist
quick understanding. Mildew and mold problems
can be difficult to control and may require
professional help by a heating and air
conditioning specialist.