Moisture Problems in the Home
Condensation can be a problem in both winter and
summer. Three conditions in the home increase the chances
that condensation will occur. The first of these is a
relatively recent phenomenon. Many homeowners have added
insulation to cut heat loss and heat gain, while others
have caulked and weatherstripped around windows and doors
to reduce the infiltration of cold air into their homes.
The same practices that trap heat in the home also trap
high levels of moisture.
A second common condition contributing to moisture
problems in Michigan homes is the existence of cool
surfaces with which interior moisture vapor naturally
comes in contact. In less energy-efficient homes, certain
locations are prime candidates for condensation problems
because they commonly have cool surfaces. These include
poorly weatherized and insulated windows (in winter),
poorly insulated exterior walls and ceilings (winter),
masonry or concrete surfaces (summer), toilet tanks
(summer) and cold water pipes (summer).
A third condition contributing to household
condensation problems is excessively high humidity levels
in the air within the home. The normal indoor humidity
range in winter is 15 to 50 percent. In the summer, the
humidity range may be higher because of the higher
outdoor humidity levels we sometimes experience then.
High Humidity Level Problems
The first step to be taken in attempting to control
condensation problems is simply to reduce the level of
humidity in the inside air.
During the winter, the humidity level you will want to
attempt to achieve in your home will depend on the outside
temperature. As outside temperatures drop, you need to
lower inside relative humidity levels to minimize
condensation.
Monitor the interior surfaces of double-pane windows
during winter. If running water (condensation) is
apparent on them, the interior relative humidity level is
too high and should be lowered.
Levels to achieve in summer are somewhat more
arbitrary---they depend mainly on how uncomfortable you
are in high humidity conditions.
Summer Problems
During the summer, one of the major functions of an
air conditioner, in addition to cooling warm interior
air, is removing humidity from the home. A second
alternative available to lower summertime humidity levels
is to purchase and operate a dehumidifier. If humidity
levels remain high in winter, you may need to run it
then, too. Though both air conditioners and dehumidifiers
are effective solutions to excessive moisture problems,
they are relatively expensive to buy and costly to
operate. Expect increases in your electricity bills
during the months you use them.
Houses on Crawl Spaces
In homes built on crawl spaces, evaporation of
moisture from the earth is a major source of household
humidity. The high levels of humidity in crawl spaces can
be a problem in both summer and winter. Foul odors in the
home or crawl space, mold and mildew growth in the
interior of the home (especially in closets) and growth
of fungi in the crawl space itself are signs of the
problem. Covering the crawl space ground with a vapor
retarder (polyethylene or heavy plastic sheets available
at lumberyards) is crucial in preventing moisture
problems in crawl space homes.
In addition to a vapor retarder covering the ground, crawl
spaces should be provided with adequate natural
ventilation to facilitate air movement throughout the
space. If a vapor retarder is present in the crawl space,
1 square foot of free vent area is required for every
1,500 square feet of crawl space ground area. Without a
vapor retarder present, 1 square foot of free vent area is
required for every 150 square feet of crawl space ground
area. Most crawl space vents include louvers and/or
screens to prevent the entry of insects and small animals.
These coverings slow air circulation and cut down on the
vent's effectiveness. Thus, you will need to double the
amount of ventilation needed in most cases to compensate
for this reduction. Locate vents near corners and across
from one another to facilitate air movement through the
crawl space.
Attic Ventilation
Adequate natural ventilation is important in the
attics of homes as well. If a vapor retarder is not
present in the ceiling to slow migration of moisture from
the home's interior into the attic, attics require 1
square foot of free vent area for each 150 square feet of
attic area. An exception occurs when the attic vents are
located in a high/low configuration (i.e., half of the
vent area in the eave/soffit area and the other half in
the roof ridge area). In that case, 1 square foot for
each 300 square feet is adequate. If a vapor retarder is
present in the ceiling, attics require 1 square foot of
free vent area for each 300 square feet of attic area.
A number of types of vents are available to provide
attic ventilation. As with crawl space vents, most
include louvers or screens to prevent the entry of
insects and rodents, and these coverings slow air
circulation. Therefore, twice the amount of ventilation
is needed in most cases to compensate for this reduction.
With or without a vapor retarder, circulation of the air
throughout the attic space would be more effective if the
vent openings were distributed equally between low areas
(eave and soffit) and high areas (roof ridge).
Mechanical Ventilation
A final method to reduce interior humidity levels is
to control in-home sources of moisture vapor generation.
The kitchen, bath, laundry and utility room are primary
moisture generation locations. Consider
installing exhaust fans or vents in both the kitchen and
the bathroom if they are not present. The vents should be
ducted directly to the exterior of the home rather than
to an attic or some interior space. Clothes dryers should
always be vented to the outside as well. Removing
moisture and depositing it outside is an effective way to
control condensation problems in both winter and summer
months.
Three additional sources of moisture periodically
cause problems for homeowners: humidifiers, new
construction or remodeling, and malfunctioning combustion
appliances.
Humidifiers
Many homeowners use humidifiers to add moisture to
their homes in winter. In the past, when homes were leaky
and so less energy efficient, much of the moisture
generated inside the home went out with the warm air
escaping around and through windows and doors.
Overly dry air-was common, and people experienced
static electricity buildup on carpets and clothes,
breathing difficulties due to dry nasal passages and
somewhat destructive overdrying of furniture. To combat
this dryness, they commonly used humidifiers. Some were
incorporated directly into forced air heating systems, and
moisture was circulated in the home along with heated air.
A second type of humidifier, the free-standing model, is
portable and can be moved freely around the home to
provide moisture where it is most needed. Whether you have
extensively weatherized your home or not, experiencing
condensation problems means you should not use a
humidifier.
Construction Moisture
Homeowners who move into a: newly constructed home or
complete remodeling projects often experience high
moisture levels in the interior as the building materials
and systems dry. If it is necessary to close the house
because of cold weather, the problem may seem excessively
serious. Over time, the building materials will dry and a
form of equilibrium will be established. In the meantime,
airing the house when you can and using exhaust fans will
help to move the moist air to the outside.
Malfunctioning, Combustion Appliances
Oil- or gas-fired heating, appliances that are not
functioning properly or unvented heating units can cause a
buildup of moisture in a dwelling. If you suspect any
combustion appliance in your home is not functioning
correctly, have a repair person inspect it. Heating
systems, in particular, should be regularly inspected and
adjusted by a heating contractor. Oil-fired furnaces need
annual inspections. Gas-fired systems, depending on their
age, can be inspected less frequently, though three years
is the maximum time a gas-fired unit should go without
being serviced. If you use unvented space heaters in the
home, follow the manufacturer's use and maintenance
instructions carefully.
Cool Surface Condensation Problems
In less energy-efficient homes, cool surfaces are
readily available for water vapor to condense and collect
on. Warming these surfaces by adding insulation or
cutting down on the amount of cold air that can get to
them by caulking and weatherstripping will lessen
condensation problems.
Window Surface Problems
Condensation on window surfaces in cool or cold
months can be controlled by adding layers of glass in the
form of storm windows or using double- or triple- glazed
window units, installing a plastic film on the outside or
inside of the window frame (a less expensive way to add
storm window protection), repairing broken glass, and
sealing any leaks in and around the window with
weatherstripping and caulking on both the inside and
outside.
A number of bulletins available at your county
Cooperative Extension Service office provide information
on caulking and weatherstripping procedures. Ask for
Extension bulletins E-1104, Weatherstripping your Doors
and Windows (covers weatherstripping, caulking, adding
storm windows); E-1573, Caulking and Weatherstripping,
Exterior Peeling Paint and Ceiling/Wall Discoloration
Problems
Peeling exterior paint and discolored interior walls
and ceilings (usually in the form of mold or mildew
growth) are good indications that condensation is
occurring inside wall cavities and attics. During winter,
cold outside air collects in these areas and can cool
attic, ceiling, wall cavity and interior wall surfaces to
the point where condensation occurs. Adding insulation to
these areas will warm these surfaces and thus help
prevent condensation. Vapor retarders should be used in
conjunction with the added insulation to prevent the
migration of vapor into these areas from the interior of
the home. Note: specially formulated vapor retarder
paints are available on the market. They seem to be the
least expensive and the easiest way to create a vapor
retarder on the winter warm side of the ceiling or wall
when insulation is added to these areas.
Sealing Interior Cracks and Holes
When you add insulation, be sure to repair, caulk or
weatherstrip any holes or cracks in ceilings, walls and
floors and along baseboards. These are prime areas for
moisture migration to occur. Moisture vapor moves with
air, and any cracks or holes that allow air to flow
freely through them are potential trouble spots. Recent
findings indicate that the sealing of these small, often
overlooked areas can be a major factor in solving
moisture problems occurring in attics and wall cavities.
For additional information on weatherizing, consult
Extension bulletins E-813, Weatherproofing Michigan
Homes,; E-1103, Insulate Your Unfinished Attic, and
E-816, Wall Repair and Fasteners.
Basement Wall Condensation Problems
Adding insulation to basement walls has advantages
similar to adding it to wall cavities and the ceiling: it
eliminates cold surfaces where condensation can occur,
and it cuts energy costs. Basement walls are often
insulated by adding furring strips to the walls and
installing rigid or batt insulation between the furring
strips. If you use batt insulation, install a vapor
retarder such as polyethylene film on the winter warm
side of the batt insulation to prevent future moisture
migration into it. To achieve a finished effect, place
drywall over the vapor retarder. (Note: There is some
question about using a second layer of polyethylene when
batt insulation is used on basement walls.)
Rigid insulation is relatively impervious to water
and moisture vapor damage. Therefore, it does not require
the addition of a vapor retarder over or behind it when
it is added to basement walls. As with batt insulation,
drywall can and should be used over rigid insulation to
provide a finished look and, in accordance with building
codes, to provide a fire protective covering over the
material that separates it from a habitable living space.
Procedures for adding insulation to basement walls are
described in Extension bulletin E-1105, Insulate Your
Basement Walls, available at your local county
Cooperative Extension Service office. Keep in mind, too,
that if condensation is occurring in the basement during
humid summer weather, windows and doors to the basement
should be closed to help keep the humid air out. Open
doors and windows when outside humidity levels are low to
introduce dry air into the basement.
Toilet Tank and Water Pipe Surfaces
Toilet tank surfaces are another common place for
condensation to occur, particularly during warm, humid
months. Warm toilet tank surfaces by either installing
rigid waterproof insulation on the inside of the tank or
adding a mixing valve to the cold water supply line. This
introduces hot water into the tank water supply and can
help warm the tank to a level that prevents condensation.
Install tubular or wrap insulation around water pipes to
prevent condensation there.
Seepage and Leakage
Seepage or leakage problems commonly occur in the
basement or crawl space in the early spring when snow and
ice are melting and frost is beginning to leave the
ground. They can also occur in the spring, summer and
fall during and after heavy rains.
Seepage in a basement is the slow (non-pressurized)
movement of groundwater through the basement walls. It may
appear as a damp spot in an isolated area or in many
spots. Leakage, on the other hand, is the fast
(pressurized) movement of groundwater through the wall. In
the case of leakage, the entry routes for the water are
cracks or joints in the wall; with seepage, the water
migrates through pores in the wall material.
Two conditions must exist for seepage or leakage to
occur. First, the soil near the basement or foundation
walls must be wet or saturated. Second, the basement or
foundation wall must have a weak spot where water
infiltration can occur.
Soil Saturation
Wet or saturated soil near basement walls can have
several causes: improper disposal of roof water runoff,
poor surface drainage away from the house, separation
between the basement or foundation wall and the soil
surrounding it (this crack acts like a funnel), window
wells collecting rain water, lawn sprinklers located too
close to the house, an inadequate below-ground footing
drain system or a high water table.
Once the soil is wet or saturated, cracks, weak joints
or pores in the masonry provide a route through the
basement or foundation wall.
Alleviate wet or saturated soil near the basement
walls by minimizing or eliminating the moisture at its
source. The installation, repair and maintenance of the
gutter, downspouts and eavestrough discharge system are
necessary to minimize the poncling of roof water runoff
close to the foundation. Eavestrough discharges
should terminate at least 3 feet away from the basement/
foundation wall and gently slope away from the foundation
at least 1 inch per foot of discharge run.
An adequate ground slope away from the
basement/foundation wall is needed to ensure that
rainwater will be distributed away from the foundation.
Generally, a slope of 6 inches in a 10-foot run of ground
is adequate. All pockets or openings between the soil and
the foundation should be filled with clean material
that has good drainage characteristics, such as pea gravel
and sandy soil.
Window well covers should be installed so that
rain-water will not collect in the wells. Locate lawn
sprinklers so they don't sprinkle the walls.
A sump pump can be attached to the footing drain tile
(a building contractor will be needed for this unless you
are an experienced do-it-yourselfer) to drain excess
groundwater away from the tile system and discharge it
into a sump well set in the basement floor. In turn, the
sump can then pump the waste water into the storm sewer
system or to a ground area adjacent to the house. Choose a
spot where the water will not damage the foundation or any
adjoining property. Contact your local township or city
building officials for specific guidelines on where to
dispose of sump pump discharge.
Wall Repair and Conditioning
If the seepage or leakage is occurring through a
small, visible crack, use a wire brush to clean the crack
and fill it with mortar cement or hydraulic cement. For
larger cracks, chisel out a dove-tail groove and clean
and fill the groove with either mortar or hydraulic
cement. If leakage is heavy or under pressure,
you may need to install weep pipes to direct the leakage
to a sump pump or drain. A professional may have to be
hired to help with these methods.
An additional solution for serious basement moisture
seepage/leakage problems is installing a footing drain
tile system around the exterior walls. While this is
being done, the exterior side of the foundation walls
should be waterproofed. This solution involves
excavating the soil around the exterior walls, installing
a footing drain tile system, waterproofing the wall,
backfilling with clean and porous material, and sloping
the backfill away from the walls. Contact your local
township or city building official to secure information
about discharge of footing drain tile water.
The addition of a footing drain tile, weep pipes and
the procedures involved in attaching an existing footing
drain tile to a sump pump are expensive and time
consuming. Consult an experienced building contractor,
engineer or architect before attempting these solutions.
Before you hire anyone to do such a job, look for
background information about these people. How long have
they been in business in or near your community? What type
of reputation do they have with local banks, savings and
loans associations, or lumberyards? Are they licensed ?.
Ask for the names of at least three references
who have had work similar to your done by the individuals
or their companies. Ask these people if they were
satisfied that their problems were correctly identified
and solved. Finally determine if working arrangements and
business dealings between the references and the
contractor were comfortably and professionally handled.
Conclusion
Finding solutions to moisture problems, be they
condensation or water problems, is often a difficult,
time-consuming and expensive undertaking. The first step
in any situation is to identify the source of the
problem. This may not be easy because two and often more
things may be working together to create the problem.
Once you know the source, rethink the basics about
condensation and/or water problems. What are the no-cost
or low-cost solutions you can try first? Can the
solution(s) attempted help you in other ways in addition
to solving the moisture problem? The addition of storm
windows, for example, can cut heating costs as well as
help prevent fogging or icing of windows. In such a case,
the cost of the solution may be well justified. In some
cases, you may find you have to rely on outside help,
such as contractors, engineers or architects. Do look
into the backgrounds of these people to ensure that you
are getting the best help available and that the
solutions they offer will indeed solve the problems.