State University Extension
Home Maintenance And Repair - 01500575
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
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.
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
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.
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
(Vis. 2) 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
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.
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.
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
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
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, http://www.msue.msu.edu/msue/imp/mod02/01500181.html
and E-954, Replacing Broken Window Glass. http://www.msue.msu.edu/msue/imp/mod02/01500161.html
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. http://www.msue.msu.edu/msue/imp/mod02/01500192.html
They are all available at your county Cooperative Extension Service
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
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.
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
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
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
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 with the state of Michigan? The State Licensing and Regulation
Department can tell you. Contact it at (517)335-1669 or 337-0678. 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
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.
This information comes from Michigan State University Extension
bulletin E-2109, Moisture Problems in the Home.
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status. Issued in furtherance of MSU Extension work, acts of May 8 and
June 30, 1914, in cooperation with the U.S. Department of Agriculture.
Thomas G. Coon, Director, MSU Extension, East Lansing,MI 48824. This
information is for educational purposes only. Reference to commercial
products or trade names does not imply endorsement by MSU Extension or
bias against those not mentioned.
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