Ways to Prevent Mold
Mold Prevention & Control Tips
instead of Reactive
only factor that can be controlled is moisture."
Association of Home Builders (NAHB)
statement on controlling mold
way to control indoor mold growth
is to control moisture.”
U.S. Environmental Protection Agency
instead of Reactive
Once mold infests the home, it is
very expensive to clean up. To make matters worse,
many home insurance companies are denying mold claims.
Mold causes strong allergic
reactions in many people. If the mold level is high
enough in the home, or if those exposed have
vulnerable immune systems (e.g. children, elderly), it
can also cause neurological effects.
Value of Home
Mold infestation can cause the value
of your home or building to drop tremendously. If it
has not been cleaned properly through expensive
remediation efforts, it may not even be
Mold Prevention & Control
1. Controlling Humidity
Level (Relative Humidity)
2. Monitoring Relative Humidity
4. Preventing Water Leaks / Water Intrusion
5. Basements / Crawl Spaces
6. Ductwork / HVAC System
7. New Construction
8. Dirt / Dust Removal
10. Properly Vent Combustion Appliances
11. Keep Firewood Outdoors
12. Shower Curtains
13. Air Purification
Controlling Humidity Level
humidity level in any part of your home or building approaches
or exceeds 55% Relative Humidity (RH), then it needs to be
corrected. Toxic molds and other forms of biological
contaminates (like dust mites) will thrive and expand in this
type of atmosphere.
There are two
elements to controlling humidity levels:
Monitoring Relative Humidity
It is absolutely
vital to know whether or not you have a humidity problem. Not
only do you need to know "if", but you also need to
know "where" (which areas or rooms) a humidity
problem may exist, since the humidity level will not
necessarily be consistent throughout a home or building.
you will not know if something needs to be done to correct the
problem, or where you need to focus your efforts.
monitor the relative humidity level throughout the home or
building, you will need relative humidity sensors, also
known as hygrometers or moisture meters.
Humidity Sensor Buying Guide
you should monitor Relative Humidity (at least
- Each of the rooms
- Attic, space
between roof and ceiling
- Basements, crawl
- In wall cavities
especially closer to air handler (nearby where
filter is installed)
- Closets, food
Series Humidity Sensors
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Humidity Sensor Buying Guide
you find through monitoring the relative
humidity that your home or building (or certain areas
within it) has chronically high relative humidity (55% or
more), then you will need to use dehumidifiers. Dehumidifiers
will control the humidity level, which will help minimize
toxic mold and other microbiological contaminates.
dehumidifiers, it is more effective to use multiple room
units, as opposed to a single large unit that attempts to
dehumidify a large area. It is also affordable to include a
few small-area units for bathrooms, closets, cabinets,
etc. Dehumidifiers can reduce the humidity in the room or area
where they are placed, but a single unit will not impact the
humidity level beyond this area very much, if at all.
are other factors to consider with dehumidifiers:
- Water extraction
(measured in pints)
- Automatic tank shut off
(when tank is full)
- Air filtration
- Anti-frost sensor
- Efficient air flow
- Water pumped out of
- LCD screen
- Fan speeds
- Energy consumption
- Chassis material
- Lowest temperature at
which it can operate
- Noise level
Leaks / Water
Other than just having a high humidity level
in the home (due to humid climate), water leaks and other
forms of water intrusion into the home or building is the most
common reason a toxic black mold problem originates.
Below are types of water leaks and places
where unwanted water can enter the home, and ways to avoid
these types of water intrusion problems.
Condensation or rusting on or
around a pipe is a sign of a leak. Covering
cold surfaces, such as cold water drainpipes, with insulation
helps to prevent condensation.
difficult part of preventing leaking pipes is determining
whether or not they are leaking in the first place, since they
are normally concealed from view.
some signs to look for:
You can hear running water sounds when nothing
is turned on.
Musty odors that seem
to originate from walls or floors.
Running toilets and
Abnormally high water
A water meter reading
that changes when you aren’t using any water for an hour.
Discolored or damaged
A cracked or damp
foundation or slab.
Warm spots on concrete
slab floors, mildew, or excess moisture under carpets.
Regular sewer backups.
Areas in the yard that
are too wet and with unusual plant or grass growth.
To prevent water from collecting around the
foundation, and seeping up through the walls, make sure the ground
slopes away from the foundation.
Here are some additional tips in
preventing water seepage through the foundation:
Ensure the floor is well ventilated and walls
are properly sealed against moisture entry. Polythene put over
damp ground can help prevent dampness rising into the house.
Insulate your home properly.
In the winter, insulated ceilings, walls and floors
have temperatures similar to those of the warmer air inside
the home, therefore condensation is less likely to form.
Prevent rising damp
from entering a foundation wall by improving your home’s
perimeter drainage. Direct
all surface rainwater away from the home through drainpipes,
culverts, French drains, etc.
If no other methods
are feasible, a last resort would be to install either a
physical or chemical horizontal damp-proof course.
Ways to Inspect for a Roof Leak.
common cause of leaks is from cracked or damaged
chimneys. Look for loose brick, cracked mortar joints, and
a solid metal or concrete cap on top.
for water stains on the inside ceiling, and on the
beams in an attic. Beams
that have been exposed to water will become weakened and cause
a sag in the roof.
for any visible damage such as cracks, tears, splits.
These will most likely lead to leaking.
inspect all roof penetrations (i.e. skylights,
chimneys, vents, etc). Look
for signs that the cement is separating from the surface,
especially at a vertical penetration of the roof.
areas where different materials meet such as metal to
brick, shingles to metal, etc. These
surfaces expand and contract at varying rates and will pull
away from each other. Make
sure the seals between materials are tight, not loose.
can attempt to find a leak from the inside by using a
flashlight and tracing the leak uphill.
How to Protect/Maintain the Roof.
your roof at least twice a year.
Especially proceeding harsh weather conditions and
will weather under the heat/sunlight.
It can essentially be “baked” and become dry and
brittle (alligatoring), hence it is more likely to split and
eventually leak. Metal
components of the roof can rust and corrode, and asphalt-based
plastic cement used for seals around pipes, vents, and other
penetrations may deteriorate over time and leak.
You can apply a coating to some roofs to create a layer
of waterproof protection.
Ice Dams and Leaks.
caused by ice dams occur when warm, heated air from the home
begins to migrate through the insulation and into the attic
area of the house. Without proper ventilation, this warm air
collects in the attic area and may warm the underside of the
outside temperatures keep the top outside layer of moisture
frozen and the warm decking melts the bottom layer of ice
turning into liquid water. This water will run down the
shingles until it meets the "dam" at the gutter
line. With no escape route, the water pools, then backs up
underneath the shingles and enters the attic area through nail
holes and seams in the roof decking
4. Ways to Minimize the Occurrence of Ice Dams.
the attic adequately insulated.
not cover the attic soffit air intake vents with insulation
(add these to your home if you don’t have any).
attic has sufficient air exhaust outlets and airflow is
distributed evenly throughout the attic (peak mounted
ridgevents maximize air flow).
ice and water shield can be installed at the eaves of the home
and under the shingles to prevent water from entering the
electric heat tapes in the gutter system.
Condensation on or around the window is the
sign of a excessive moisture. If this is happening, use a sealant
around the window to make sure that it is completely air
Taking measures to reduce water leakage
through the roof, leaky pipes,
and the foundation (see above
for each of these), as well as through the gutters
(below) will go a long way in keeping the walls from
collecting too much moisture.
In addition to this, make sure that the air
pressure is not too high on the positive side (see
Ventilation tips below). However, you do want the air pressure
inside to be slightly positive.
Also, make sure that the relative
humidity level is below 55% to prevent your walls from
taking in too much moisture (Relative
Humidity Sensor Buying Guide). Use dehumidifiers if
Clogged or faulty rain gutters can cause
excessive water leakage through the walls, roof, and
foundation of the home. You can clean
your rain gutters with a light broom, a garden hose with a
controllable-spray nozzle, or by using one of many
gutter-cleaning devices on the market.
Adding perforated covers over your
rain gutters will cut down on the frequency of cleaning.
Rainwater and some dirt/small debris can permeate the cover
but large debris, such as large leaves and twigs, cannot.
These covers can typically be found in a local hardware store
for only a couple of dollars for about every 4-feet of length.
Make sure your gutters' downspouts
are properly cleaned too. Spray water into the gutter or the
top of the downspout to ensure it drains freely and with no
obstructions. Water must also be diverted away from your
If you don't have a spout going directly
into a drain system in your yard and toward the street or a
drainage basin, use splash blocks. These relatively
small devices will channel the water from your downspout and
away from your home and only cost a couple of dollars.
Click here for more
on basements and crawls spaces.
Put a plastic cover over dirt in crawlspaces
to prevent moisture from coming in from the ground. Be sure
crawlspaces/basements are well ventilated with good
cross ventilation under the house so air will circulate
freely. Make sure all
vents are unobstructed and repair any torn vent screens.
If you don’t have sufficient vents, add more.
Get your basement
waterproofed through a professional service:
Seal you concrete yourself against water and
vapor with RadonSeal deep-penetrating concrete sealer
practices to prevent moisture in a new home, particularly in
selection. The first and perhaps most important step is to
select a suitable site. Moisture problems are greatly reduced
if a home is built on a site with a high water table.
drainage. Landscaping should be graded/sloped to direct
rainwater and melting snow away from the foundation. At least
six inches over the first ten feet from the foundation wall.
A dampproof coating on the below grade portion of the
foundation wall. Tell your builder you want a high quality,
durable waterproofing. A thin dampproof coating is vulnerable
to damage during construction.
slab. The basement floor can be a significant source of
moisture. To reduce water absorption, the concrete slab should
be poured on top of three to four inches of washed aggregate,
with a sheet of polyethylene installed beneath the aggregate.
Insulating the floor slab saves energy and improves comfort;
it also reduces basement condensation in the summer.
system. An effective exterior drainage system drains bulk
water away from the foundation. A channel of coarse rock or
drainage tile may be used. The drainage system must be
installed on the outside, and near the bottom of the footing
wall insulation. Foundation insulation may be placed on
the exterior wall, be an integral part of the wall, or placed
on the interior of the foundation wall. Regardless of where
the insulation is placed, a moisture barrier is required to
reduce outdoor moisture from coming through the foundation
wall. In the case of insulation placed on the interior side of
the foundation wall, both sides of the insulation must be
protected. A moisture barrier is required between the
insulation and the wall from floor to grade, and a vapor
retarder is required on the interior side of the insulation.
To keep water out of crawlspaces, dig ditches
around the sides of the house down to the footing.
Install gravel and drain lines that are sloped
about 2 inches per 10 feet to carry water away from the house.
Direct the water to a natural drainage, to the street,
or a French drain. Before
backfilling, place waterproof membranes against the foundation
wall. Also, ensure
water from downspouts is directed away from the house.
Ductwork / HVAC System
Sanitize Cooling Coils
sure you periodically wipe any biological growth from the
coils. Condensation is continually dripping off the coils when
the HVAC system is running. This condensation provides a
perfect place for mold to grow. In
which case, disinfectant should be periodically applied
to the coils.
This is where the condensation
from the cooling coils drips. If you have a flat drain pan,
the stagnant water will become infested with mold growth. In
which case, a sloped drain pan should be used, so the
water runs off to the proper location. You also need to
check to make sure that drain lines are flowing
addition, the drain pan should be cleaned with a disinfectant
on occasion, and should be replaced when corrosion
your HVAC filters on a regular basis. If this is not done, the
filter itself can become a fertile breeding ground for
all the molds and other biological contaminates that are
collected. Once this happens, the spores from the mold will
multiply, and will be circulated throughout the
home or building through the ductwork.
you have insulation lining the interior of the
ductwork, then it should be removed, so you are left
with bare sheet metal. The fiber glass insulation collects a
lot of dirt and dust, which provides a good habitat for mold
colonies. Once the mold begins to grow inside the ductwork,
the mold spores will be spread throughout the house when the
HVAC system is running.
in the HVAC System
In many cases, mold problems can be avoided
or caused during the construction of a home or building. In
which case, you can take precautions during this phase to save
yourself mold headaches down the road.
First, review many of the tips on this
page to make sure that the house is built in such a way
that as many of these as possible can be put into place.
addition, avoid using moldy materials, ensure that any
fake stucco that is used is installed 100% properly, since
this is a common cause for mold growth in exterior wall
cavities. If you are really adamant about preventing potential
mold problems, then you may want to avoid using fake stucco
/ Dust Removal
An environment that is "dirty" or
"dusty" is far more conducive to mold problems than
a clean environment. Dirt, dust, and grime are often composed
of organic material, which is a staple of the the toxic
"black" mold diet.
House dust also serves as a means for
locomotion for mold spores, enabling them to spread
throughout the home more effectively.
Proper ventilation can reduce moisture in
the home. Keeping the air pressure in the home or
building at a slightly higher level than the air
pressure outside will help to ensure proper ventilation.
Slightly positive air pressure forces moisture and
If the air
pressurization is the other way around (negative), where the
air pressure is higher outside, then it will force moisture
and pollutants back into the home or building.
over-pressurization though (too much of a positive air
pressure), since it will cause moisture to be forced into
walls and structural cavities, compounding the moisture level
inside, and potentially damaging the home or building.
order to achieve a slightly positive air pressure, adjust the
supply ventilation slightly higher than the exhaust
Also, try to ventilate
appliances and bathroom/kitchen fans outside if possible.
Vent Combustion Appliances
appliances include space heaters, ranges, ovens, stoves,
furnaces, fireplaces, water heaters, and clothes dryers.
these appliances are safe. However, the combustion process
always produces water vapor, if the appliance is not
properly vented, it can lead to increased amounts of moisture
in the home and provide an ideal environment for mold growth.
of properly venting combustion appliances include
equipping ranges with hood fans that are exhausted to the
outside, keeping doors open to rooms where these appliances
are operating, making sure that the vents are connected and
unblocked, and that there are no holes or cracks in the
ventilation systems. Finally, make sure that you follow
manufacturer instructions when installing and using combustion
Firewood often has a little mold growth on
it before being brought indoors, since it contains nutrients
for mold to grow and thrive. This is not a problem if kept
outdoors, but the mold growth can really progress if the
firewood is kept in contained areas.
shower curtains when mold begins to become visible.
may want to use an air
to minimize the airborne particulate, which allows mold spores
to disperse to other areas of the home or building.
To neutralize something as difficult as mold,
an air purifier with multiple technologies is needed (Air
Purification Buying Guide). HEPA filters and ionizers
combine to effectively capture the allergenic spores
released into the air (HEPA stands for High Efficiency
Particulate Arrestor). Germicidal UV light purification is
also important to destroy the toxic micro-organisms
associated with mold.
Air Purifier with Hepa filtration,
germicidal UV light and ionizer:
The Multi-Tech air purifier will capture
mold spores and
disinfect the trapped micro-organisms.
Humidity Sensor Buying Guide