questions on moisture on windows

[BRJ]

Does anybody know why all our indoor windows have heavy moisture when we get up in the morning...太多水气, 以至于window frames 有酶点...we already turned off humidifier, but it still not change...thanks

 

[newer]

type "condensation on Windows" in Yahoo and Google to find solutions.

Introduction

Every year, with the arrival of cold, winter weather, questions about condensation arise. The moisture that forms on window glass, obscuring the view, freezing or even collecting in puddles on the window sill, can be irritating and possibly even damaging. The first reaction may be to blame the windows for this problem, yet windows do not cause condensation. Excessive water vapor in the air, the temperature of the air and air circulation or movement are the three factors involved in the formation of condensation.
Today’s modern homes are built very “air-tight” for energy efficiency. They provide better insulating properties and a cleaner, more comfortable living environment than older homes. These improvements in home design and construction have created some new problems as well. The more “air-tight” a home is the less fresh air that home circulates. A typical central air and heat system only circulates the air already within the home. This air becomes saturated with by-products of normal living. One of these is water vapor.
Excessive water vapor in the home will most likely show up as condensation on windows. Condensation on your windows is a warning sign that the relative humidity (the measure of water vapor in the air) in your home is too high. You may see it develop on your windows, but it may be damaging the structural components and finishes through-out your home. It can also be damaging to your health.
The following review should answer many questions concerning condensation and provide good information that will help in controlling condensation. (top)

What is condensation?

Condensation is the process by which water vapor becomes a liquid. The air in our atmosphere contains anywhere from 0 to 4 % water vapor. This water vapor will remain in the air until either 1) so much water vapor is added to the air that it becomes saturated and can no longer hold the water vapor, or 2) the temperature of the air drops low enough that the air can no longer hold the water vapor. In either case the water vapor turns into liquid and forms on a surface as condensation. (top)

What does it indicate?

When you see condensation forming on your windows it is a warning that there is too much water vapor in the air of your home or that there is insufficient air circulation next to the windows on which the condensation is occurring. (top)

What causes condensation?

Condensation is caused by the air temperature becoming too low to hold the water vapor that is in it. The factors involved in condensation are as follows:
1. The amount of water vapor in the air of the home (measured in relative humidity).
2. The circulation of the air within the home.
3. The air temperature. Both in the home and outside.
The air in a room contains water vapor. The amount of water vapor in the air varies and is commonly expressed in terms of relative humidity. Relative humidity is the measure of the amount of water vapor actually in the air compared to the maximum amount of water vapor the air can hold at that particular temperature and pressure.
The fundamental principle concerning air and relative humidity is: the warmer the air temperature, the greater its capacity for holding water vapor. When warm air in a room comes in contact with a cold surface the air around that surface begins to cool. As it cools its ability to hold water vapor decreases. Eventually, it reaches a temperature at which it can no longer hold the water vapor. This is sometimes referred to as the dew point. When the air reaches this point the water vapor begins to condensate, forming as tiny droplets of water on the cooler surface. Often times the glass in your windows is the coolest visible surface and this is why you may see condensation develop there first. (top)

Where does water vapor come from?

Water becomes vapor by a process known as evaporation. Evaporation is the opposite of condensation. The air in a home gains water vapor by evaporation from a number of sources. The most obvious are running water in sinks, baths and showers, washing machines, and cooking. Some less obvious sources may include house plants, the ground beneath the house, leaky basements, humid outside air allowed in through open windows or doors, any new construction materials and even the air that you exhale contains water vapor produced by your body.
Newly built or remodeled homes will acquire excessive amounts of water vapor from the new materials and finishes used in the project. As the water evaporates from these materials it will cause high levels of relative humidity in the home until the materials stabilize and the humid air is properly vented. (top)

How does air circulation affect condensation?

Air circulation affects the supply of fresh air to the living areas of your home. Poor air circulation within your home will cause the air next to your windows to cool down quickly. When air remains still, next to a cool surface, it cools down sooner than air that is well circulated. As the room air temperature decreases its ability to hold the water vapor in it decreases. Using the same principle as a defroster in an automobile, suppling fresh air circulation to the glass area slows down the cooling process and reduces condensation.
Drapes, blinds or other coverings tend to trap air next to the window greatly reducing the air circulation around them. Bay and bow windows and other windows that extend from the walls of the home outward are also susceptible to air circulation problems. (top)

What about air quality?

Not only is it important to have good air circulation in a home, but the quality of the air that is being circulated is very important. The new home construction designs and materials that are used today help make the homes more energy efficient and air-tight. This has greatly affected the quality of the air in the home. Most heating and cooling systems are used as the primary air circulation system. In a modern air-tight home, these systems will only circulate the air already within the home unless a fresh air supply system is also used. Fresh air supply is mandatory to properly vent and maintain humidity levels in the home. (top)

How does the temperature affect condensation?

The amount of water vapor air can hold is directly related to the air temperature. Warmer air can hold more water vapor than cooler air. When warm air is cooled it looses its capacity to hold water vapor and, if it cools enough, it will begin to condensate.
It is important to remember that relative humidity is not the measurement of the actual amount of water vapor in the air, but rather the amount of water vapor present compared to the maximum amount of water vapor the air can hold at that particular temperature and pressure. For example: The air temperature in a room is 70° and it has an amount of water vapor that produces a relative humidity of 50%. Without changing the amount of water vapor, the air temperature is lowered to 50°. This changes the relative humidity to 100%. The air is now holding its maximum amount of water vapor for that temperature. It has the same amount of water vapor, but because of the lower temperature the relative humidity becomes greater.
During the heating season the air temperature in your home will probably be maintained at a fairly constant temperature. The real affect of temperature will be the relationship between the indoor air temperature and the outside temperature. The colder the temperature outside the colder the glass surface temperature will become as well as the air temperature in the hidden structural areas of your home. As these areas cool down the air near them begins to cool as well. The air temperature in the room may be relatively unaffected, but the air next to the window glass or in these hidden areas will cool down. The air in these areas may cool below its maximum vapor saturation point and condensation will begin to form. (top)

What about EIFS / Synthetic Stucco?

Serious concerns have been raised regarding Exterior Insulation Finish Systems (also known as EIFS and Synthetic Stucco) and excessive moisture problems in buildings using this finish system.
Many experts agree that it is common to expect some amount of water or moisture to enter almost any building exterior system. The building exterior system should allow that water or moisture to drain or “weep” back out to the exterior. Most exterior systems do this. However, some EIFS systems may not allow water or moisture that enters the wall system to “weep” to the exterior. This can cause excessive moisture to accumulate within the wall, seriously damaging the wall and building. EIFS or so-called “barrier” systems have been reported to be highly susceptible to this problem.
Moisture control in any building requires proper design and construction. Proper flashing and sealing of all exterior components. The use of qualified materials and construction techniques. Following all building codes and guidelines. And professional design and workmanship of the entire building, to include moisture management systems for the entire structure.
Proper building design, materials, components and construction are the responsibility of the building designer, the contractors, and materials manufacturers. Concerns about moisture management issues should be addressed to these professionals. Sun Windows, Inc. is not responsible for problems or damages caused by inefficiencies in building design, construction or maintenance, failure to properly install our products, or the use of our products in wall systems that do not effectively manage moisture. (top)

What should be done when condensation occurs?

When condensation occurs it is important to first identify the cause before a solution can be implemented.
1. Is the home new or newly remodeled? New or newly remodeled homes will often have high levels of water vapor present in the air for the first year or longer. This occurs because the new materials used are slowly stabilizing and water is evaporating from them into the air of the home. During the first heating season, condensation will often appear on the windows, until the high level of water vapor in the air is dispersed.
2. Check the relative humidity in each room of the home. Your windows are your first gauge for measuring relative humidity. When you see condensation on the windows it is a warning sign that excessive water vapor is present. The best way to measure relative humidity in a home is to use a sling psychrometer. It will give accurate readings when properly used. Take reading when condensation is on the windows. Take readings in every room, even if the windows in other rooms do not have condensation on them. Relative humidity levels will often vary significantly from room to room. Keep a record of your readings, the time of day, the weather conditions, and the temperature outside and inside. It may be necessary to take readings more than once a day, especially if condensation occurs at a particular time each day.
3 Where is the window located? Windows that do not receive direct sunlight will probably develop condensation before windows that are exposed to direct sunlight. Windows, such as bays and bows, that extend out from the main walls of the house may be more exposed to the cold elements outside and may be isolated from good air circulation inside the home.
4. Other conditions. Window treatments like drapes, mini-blinds, and shutters can prevent good interior air circulation, cutting off air exchange near the glass surface. Windows in different rooms are likely to have different environments due relative humidity levels, the location of heat registers and other physical factors. (top)


Solutions

To control condensation it is necessary to control the relative humidity levels, air temperature, and air circulation within the home.

Controlling Relative Humidity

Relative humidity is controlled by controlling the amount of water vapor in the home. The best way to control the amount of water vapor in the home is by properly venting the home with a fresh air exchanger system. Fresh air exchangers can work in conjunction with your heating/cooling system or they can function independently, depending on the system. These systems will exhaust the moisture saturated air and continually provide a fresh air supply to the home. Additionally, use exhaust fans in the kitchen and bath rooms to remove excess moisture from those rooms. Make sure the basement or crawl space is properly sealed or protected from ground moisture. Ventilate the attic and crawl spaces to promote evaporation. Ventilate all appliances to the outside, not to the attic or crawl space. In extreme cases a dehumidifier may needed to remove high levels of water vapor. Dehumidifiers should only be considered as a temporary solution because they do not affect the source of the moisture. (top)

Controlling Air Temperature

During the heating season it is important to keep your heating system in good, efficient operation. Remember, the temperature of the air directly effects the relative humidity and the amount of water vapor the air can hold. (top)

Controlling Air Circulation

Air circulation will primarily be controlled by the heating/cooling system. The registers and return air vents should be located to provide good cross-flow. Locating the registers under windows is highly recommended. Ceiling fans and other portable fans can be be used to increase the circulation. Be careful with the use of window treatments not to isolate windows from good air circulation. (top)

Recommended Inside Humidity Levels

To control window condensation it is recommended that the humidity levels in the home be controlled. The general rule is to reduce the humidity levels as the temperature outside decreases. The following chart, developed by the University of Minnesota Agriculture Extension Service, establishes guidelines of recommended inside humidity levels at various outside air temperatures to minimize condensation on windows with insulated glass.
Room Outside Inside
Temperature Temperature Relative Humidity
70°F -20°F 15% to 20%
70°F -10°F 20% to 25%
70°F 0°F 25% to 30%
70°F 10°F 30% to 35%
70°F 20°F 35% to 40%
(top)

Install The Best Insulated Glass In Your Windows

Upgrade your windows to Sun Windows with high performance LowE/Argon insulated glass or on compatible products use Triple Glazed LowE/Argon insulated glass. Both types are designed to maximize the energy efficiency of your windows as well as provide most insulating power. The warmer you can keep your window glass the lower your chances of experiencing excessive condensation on your windows. (top)

 

[newer]

Facts About Condensation

Condensation is the fog that suddenly appears in cold weather on the glass of windows and sliding glass doors. It can block out the view, drip on the floor, and freeze on the glass. It’s annoying.

While it’s natural to blame the windows, you shouldn’t. Window condensation is the result of excess humidity in your home. And the glass only provides a visible cold surface on which humidity can condense.

The important thing is your foggy windows and sliding glass doors are trying to tell you to reduce indoor humidity before it causes hidden, costly problems elsewhere in your home.

Problems like peeling paint, rotting wood, buckling floors, insulation deterioration, mildew, and even moisture spots on ceilings and walls.

Foggy windows and sliding glass doors are the indicators, the warning signs, that humidity could be damaging your home.

What to do? We’ve compiled this Condensation Answer Book to answer that and other questions you may have about indoor humidity and condensation. We’ll start with the basics, and offer solutions and alternatives along the way.

However, some solutions to window condensation problems pose a different kind of problem – that of energy efficiency. Some ventilation techniques (e.g. opening windows to air out a home; running fans more frequently) may add slightly to a home’s energy bills. It is up to the reader to decide which solutions are most practical for him. This, of course, will depend on the severity of the condensation problems, both on windows and in other less obvious places in the home.

Finally, as you read through this information and learn the causes and cures for condensation, remember: it’s not the windows, it’s the humidity.
Humidity and Condensation

What is humidity, anyway?

Humidity is water vapor, or moisture, in the air. Usually it’s visible, but sometimes, such as with steam or ground fog, it’s concentrated enough to be seen. But see it or not, all air contains a certain amount of moisture.
Where does the moisture come from?

There are many things that generate indoor moisture. The normal perspiration and breathing of a family of four adds about ½ pint of water to the air every hour. Cooking three meals a day adds four or five pints of water to the air. Each shower contributes ½ pint. In fact, every activity that uses water (like dishwashing, mopping floors, doing laundry) adds moisture to the air. The truth is daily living activities of a family of four can add more than 18 gallons of water a week into the air in their home. And more water vapor in the air means a higher indoor relative humidity.
What’s relative humidity?

Air can hold only a limited amount of water vapor, and that amount depends on the air temperature. When air at a certain temperature contains all the vapor it can hold, it’s said to have a relative humidity of 100%. Thus, when it holds only half the water vapor it can hold, the relative humidity is 50%. Cooler air is capable of holding less vapor than warmer air. So air at 30º F and 100% relative humidity actually contains less water than air at 70º F and 100% relative humidity.
Just what is condensation?

Fog on windows is a form of condensation. So is the water that forms on the outside of a glass of iced tea in the summer. It all comes from water vapor in the air.
What causes it?

Excess moisture in the air. When warm, moist air comes into contact with cooler surfaces, the moisture condenses. That’s because the cooler air surrounding cooler surfaces can’t hold as much moisture as warmer air.
What does condensation on windows mean?

Window condensation can be a danger sign. It may mean that excessive indoor humidity could be doing unseen damage to other parts of your homes.
How do I know if I have excess indoor humidity?

Check for damp spots on ceilings and room-side surfaces of exterior walls, particularly closets. Look for water and ice on windows. Even water-filled blisters on outside paint surfaces indicate excessive indoor humidity.
What does excess humidity do to my home?

Excess humidity contributes to the deterioration of a home. Excessive humidity can pass through walls and freeze in the insulation. In spring it melts, damaging your ceiling and walls. Or, humidity can force its way out through siding to form blisters under your exterior paint.
You mean moisture can actually go through walls?

You bet. It’s because of a force called "vapor pressure". Moisture in wet air tries to flow toward drier air to equalize itself. This flow acts independently of air currents. In winter, inside air is much more humid than colder outside air. So, the vapor pressure, or equalization process, actually forces the inside moisture through cement, wood, plaster, and brick, toward the outside.
What happens then?

Because certain varnishes and paints block the flow of moisture, condensation can occur between the inside and outside walls, or under exterior paint surfaces. It can rot a home’s wood frame and blister the paint.
Is condensation more prevalent in any geographical region?

Yes. Condensation is more apt to occur in climates where the average January temperature is 35º F or colder.
Does condensation occur only in winter?

Usually, but it can occur during cold weather anytime, and occasionally it will form on the outside of windows on hot, humid summer days, when your air conditioner has cooled the glass.
Does condensation depend on whether my home is new or old?

Generally, yes. Years ago, before the concern with energy efficiency, homes were built with less weather-tightness than homes today. Insulation concepts were not as advanced as today. Walls and ceilings were built with much more porous materials. Water vapor could easily flow in and out of walls.

Today’s homes are much "tighter". Windows and doors are built to substantially reduce air leakage. Weather-stripping, modern insulation, vapor barriers, and construction techniques, which are intended to keep out cold air, lock moisture inside. As a result, moisture created by bathrooms, kitchens, laundries, and occupants no longer flows to the outside, unless provisions for mechanical ventilation have been made. So it’s very easy to build up excessive, even harmful moisture levels in today’s homes.
Controlling Indoor Humidity

How do I measure indoor relative humidity?

To get an accurate reading, you can buy humidity-measuring instruments, called hygrometers, or sling psychrometers. Otherwise, watch your windows for symptoms of excess humidity. When excessive moisture collects on the inside glass in a living room or bedroom, you’re approaching the humidity danger level.
Isn’t high indoor humidity healthy in winter?

That’s a common belief, but there’s little evidence to support it.

Many believe that dry air increases the susceptibility to colds. But humidity in a heated house, whether it’s high or low, is not an important health factor to a normally healthy person. And there’s little scientific evidence that the health of most people will be adversely affected if humidity is kept at a level that prevents excessive condensation.
Then what are some recommended indoor relative humidity levels for winter?

The University of Minnesota Engineering Laboratories performed a series of long and careful experiments on that subject. The following table shows the maximum safe humidity for your home, paint, insulation, and structural members:

​

Outside air temperature
​

Inside relative humidity for 70-deg. F Indoor air temperature
​

-30º F or below
​

not over 15%
​

-20º F to -10º F
​

not over 20%
​

-10º F to 0º F
​

not over 25%
​

0º F to 10º F
not over 30%

10º F to 20º F
​

not over 35%
​

20º F to 40º F
​

not over 40%
​

How can I reduce inside humidity in winter?

There are at least two steps you can take to reduce indoor humidity in winter:

Control the sources of humidity. Vent all gas burners, clothes dryers, etc. to the outdoors. Use kitchen and bathroom exhaust fans.

Ventilate your home. Because outside air usually contains less water vapor, it will "dilute" humidity of inside air. This takes place automatically in older homes through constant infiltration of outside air. But again, in newer "tighter" homes, the only way outside air can get in is by ventilation. More on ventilation in the next section.
Will reducing the humidity in my home during winter help control condensation?

It’s the most practical way. Condensation indicates excessive humidity. Eliminate the excessive humidity, and you eliminate the condensation.
How can I reduce humidity in my home during the summer?

Air conditioners or dehumidifiers are your surest ways of reducing humidity to desired levels. However, in most cases, outside air will be more humid in warmer weather, and condensation on the inside of windows usually isn’t a problem.
Ventilation

How can I ventilate my home?

There are basically two types of ventilation: interior and structural ventilation.

As a temporary solution to an acute problem, open a window in each room for just a few minutes. Remember that inside air continually gains humidity through daily living activities. Opening windows allows the stale, humid air to escape, and fresh, dry air to enter.

After a shower, for example, open the bathroom window or turn on the exhaust fan, so steam can go outside instead of remaining in the home.

Structural ventilation is slightly more complex, but will save your costly repair bills in the long run. Miniature louvers in exterior walls can be installed to prevent moisture from condensing between the outside and inside walls. This will keep paint from peeling as a result of indoor vapor pressure.

Does structural ventilation include attics?

Definitely. Many homeowners cover all attic louvers in winter in hopes of saving fuel. If the attic is properly insulated, this practice can only do harm. Because the indoor moisture penetrates ceilings, then condenses on the cool underside of the roof and can even form frost. If the attic were ventilated, moisture would be transferred to the outside air.
What harm can attic condensation do?

A lot. Moisture condensing in attics produces mildew, or rotting conditions. Or it drips down to the ceiling below to damage plaster or paint. Thermal insulation also becomes wet and provides less resistance to heat loss.
Are some kinds of attic ventilation better than others?

Yes. A combination of vents at the eaves and at the gable ends is better than gable vents alone. And, a combination of continuous eaves and ridge venting is best of all. However, regardless of the type you have, there should always be at least two vent openings, located so that air can flow in one and out the other.
Just how much attic ventilation should I have?

That’s a difficult question to answer, because the size and number of vents depends on the location of the home, wind direction, physical size of the building, quality of workmanship and kinds of building materials used.

Consult a local heating and ventilating contractor, listed in the Yellow Pages. He’ll be able to tell you exactly how much ventilation your attic should have.
What about the crawl space? Should it be ventilated, too?

Yes. The crawl space beneath a house is another place where ventilation is important. The crawl space can evaporate gallons of water each day. When you seal the crawlspace, that water penetrates the floor above and causes more humidity problems in the home.

Providing foundation vents in the crawlspace reduces the humidity, and a vapor barrier (like polyethylene film) on the ground prevents moisture leakage into the house above.
How much ventilation should I have in the crawl space?

At least one vent should be located near each corner, and should be placed as high as possible, but not higher than the bottom of the joists. Plus, if you have a ground cover, one 8" X 16" vent for each 350-sq. ft. is needed, with a minimum of four vents.

Again, it’s wise to consult your local heating and ventilating contractor for number and proper placement of vents. He’s listed in the Yellow Pages.
Windows and Condensation

Do windows cause condensation?

Windows are not a cause, per se. They provide a ready medium on which the vapor can condense. But the primary cause of condensation is excessive moisture in the air. Windows are only indicators of excessive moisture.
Why do I see condensation on my windows and sliding glass doors first?

Condensation is generally seen first on windows and sliding glass doors because they tend to have the lowest temperature of any of the visible surfaces in the house.
Are windows the only place condensation is forming?

Possibly not. There’s a point between the exterior and interior walls that’s just as cold as the inside window surface. Chances are, if you can see condensation on your windows, it’s also forming between the walls, too. Room-side surfaces of exterior walls are normally warmer, but occasionally condensation occurs on cold spots such as nail heads and in the corners of outside walls and closets. This is because insulation is weaker and circulation is restricted in these areas.
What causes condensation on windows and sliding glass doors?

Recall that cool air is able to hold less moisture than warm air. Therefore, when the warm, moist air of the room comes into contact with the cool glass surface, some water vapor that can no longer be held by the cooled air is deposited on the glass.
Do drapes and window shades cause window condensation?

Drapes and other window coverings don’t cause window condensation, but they can contribute to the problem by restricting the flow of warm room air over the glass surface. Therefore, condensation is more apt to occur when drapes are closed and shades are pulled down.
What causes condensation on the inner surfaces of storm windows?

This indicates that air is leaking outward around the inner window, and is being trapped by a tight-fitting storm window. Moisture is then trapped between the panes, and condensation occurs on the outside pane. Tight storm windows should have some ventilation to the outside to relieve this problem.
What damage can excess window condensation do to windows?

It can cause the paint to peel from the sash or stain the inside. Water can run down into the window frame causing dampness around the frame. It can sometimes cause paint to peel on the outside of the window.
Are there any cases where window condensation is only temporary?

Yes, there are primarily three: new construction or remodeling; the beginning of each heating season; and quick changes in temperature.

New construction and remodeling produce a lot of moisture. Wood, plaster, cement, and other building materials contain a great deal of moisture. When the heating season starts, this moisture will gradually flow out into the air in the home. It will usually disappear during the first heating season and not cause any further trouble.

At the beginning of the heating season there may be a certain amount of temporary condensation. During the humid summer your house absorbs some moisture. After the first few weeks of heating your house will dry out, and you’ll have fewer condensation troubles.

Sharp, quick drops in temperature can also create temporary condensation problems during the heating season.
Can windows help control moisture in my home?

Only in the sense that they can be opened for ventilation. Otherwise, windows are only indicators of excessive moisture in the air.
Is there anything I can do to the windows to eliminate condensation?

If you have windows with good storm sash or double-pane insulating glass (both keep the inside glass surface warmer), there isn’t very much more you can do to the windows except possibly add triple-glazing (see below). But again, troublesome condensation indicates excessive humidity, and that problem must be eliminated at the source.
Is window condensation really reduced that much with double-pane insulating glass?

Yes. Double-pane insulating glass permits about 37% relative indoor humidity (at 70º F inside, 0º F outside) without condensation. Compare that to single-pane windows that permit just 12% relative indoor humidity (at 70º F inside, 0º F outside).
Building a Low-Condensation Home

I’m building a home. What steps can I take to prevent excessive condensation?

There are several ways you can plan your home to prevent excessive condensation:

Choose vinyl or thermally broken aluminum rather than metal for windows and doors. This will reduce the likelihood of condensation on the frame and sash. Metal frames without thermal breaks, on the other hand, conduct heat quite readily. So in the winter, the inside surface of a metal window frame is cold. When humid inside air comes into contact with cold metal, condensation, and often freezing, occurs.

Make sure the attic and crawl space are cross-ventilated. The crawl space should be covered with a vapor barrier. This will prevent water vapor from rising for the soil into your home.

If you have a hot air furnace, install an outside fresh air intake.

Make sure your clothes dryer and all gas appliances have outside vents. Water vapor is one of the products of gas combustion.

If you have a basement, take the necessary steps to prevent leakage of soil moisture into the basement. These steps will vary with soil and drainage conditions on your lot.

Make sure heat outlets are places below glass areas of windows and sliding glass doors.

Use exhaust fans in the kitchen, bathrooms, and laundry. They’ll not only help reduce excessive moisture, but will clear away stale air as well.

Select windows and sliding glass doors with double-pane insulating glass, Low-E glass or triple-glazing systems.
Summary

What steps can I take to reduce excessive humidity in my present home and control window condensation?

Recognize that the best way to stop condensation is to reduce the moisture in the inside air.

Be sure that attic or crawl spaces are properly ventilated. Add a vapor barrier to cover the earth in the crawl space.
If you have single-pane windows, install storm panels. If you have double-pane-insulating glass, install triple- glazing panels.

Be willing to try living in lower humidities.
Eliminate any sources of moisture in your home that you can control.

In winter, provide more controlled ways for moist inside air to get out. Run kitchen or other ventilating fans longer and more often than you normally do.

If troublesome condensation persists, see your heating contractor about an outside air intake for your furnace, about ventilation of gas-burning heaters and appliances, or about installation of ventilating fans. Heating and ventilating contractors are listed in the Yellow Pages.

Whey you’re planning a home, take the necessary steps outlined in this circular to prevent condensation problems. Again, work with your heating and ventilating engineer. Your gas or electric company may have a residential heating engineer you can consult.

Remember that the best way to avoid condensation is to reduce the humidity in the inside air.

Window condensation is certainly a problem. But in the vast majority of cases, it’s a problem that can be controlled or eliminated. If you follow the steps and suggestions outlined in this circular, you shouldn’t have a serious condensation problem.
​

 

[Timothy's]

1) turn furnace fan to ON, let air circle around the house.
2)turn on bathroom fan when you take a shower. turn on kitchen range hood fan when you are cooking(even when it is boiling water). There are major source of humidity in the house.
3)When you leave home to work, turn on one of bathroom fan and open a window little. Do this every few days to refresh the air.

 

[BRJ]

thanks

thanks so much for the detail information.

 

[a_little]

真是长见识。 谢谢分享。 建议列为精华贴。

 

[newer]

Opening the windows(all or some) for 10-15 minutes after lunch, dinner and showers can help a lot. Although some heat is lost, moisture goes out too and humidity will be lower in the house. Then you may feel warmer inside the house. You can even lower the temperature 1 or 2 degrees if the humidity is reduced inside your house. When humidity is high in the house, you feel colder because heat transfer is faster. Opening windows can also bring fresh air in and it is good for your health.

 

[Kay007]

If you have moisture between 2 glass. You need change your window since it is not air tight. Usually the window life is 15 years or less. special your window is wood. You can place them by yourself. Otherwise $ 260 for a window panel, not whole window. Count how many panel do you have. Cost a lot. For whole house all most @$10,000. 2 years ago, I changed by myself, just 1/3 more.