WINDOW CONDENSATION

What is Humidity?.

Each winter sees more and more homeowners vitally interested in the subject of window condensation. It's not happy interest. It stems from bad experiences with window condensation, which range from irritating to downright expensive

It may strike you as odd, but the growing condensation problems of the nation are caused by progress. Yes, if you have trouble with window condensation it's probably because you live in a "tight" modern home that you can heat for a fraction of the money it takes to heat the house your parents lived in - a home that's cleaner and more comfortable besides! A "tight" home is one that is insulated better and sealed from all outside elements better than older homes that have less problem with condensation.  The older less tight homes have many ways for the moisture to escape and therefore cause less problems with moisture.  Your condensation problems also result from widespread use of several labor saving appliances that make life easier than it use to be.

This is information that explains the moisture problem of the "tight" home. It offers suggestions for curing condensation problems in existing homes. It provides additional suggestions for you who are planning a home. You unquestionably will build a "tight" home, and there are more things you can do to PREVENT excessive moisture when you build than can be done in a home where the problem already exists.

What Causes "Trouble" Condensation

A little fog on the lower corners of your windows now and then probably doesn't bother you. It shouldn't. By the time you've thought about it a second time it has usually gone away.

What we're talking about is EXCESSIVE or troublesome condensation. Condensation that blocks whole windows with fog or frost. Water that runs off windows to stain woodwork.... or in serious cases even damage the wallpaper or plaster. It's natural and easy in such cases to blame the paint, or the insulation, or the windows, but it's wrong to blame them.

What is Humidity?.

The real villain is invisible. It's water vapor ... too MUCH water vapor. The best, usually the ONLY way to prevent this trouble is to get rid of excess water vapor. Once you've equipped your windows with good storm windows or double glazing, there isn't very much more you can do to the windows to lick condensation. Humidity, water vapor, moisture steam, they're all the same. They are all one form of water. Humidity is an invisible gas. It is in varying quantities in nearly all air. THIS MOISTURE IN WET AIR TRIES TO FLOW TOWARD DRIER AIR AND MIX WITH IT.

Scientists describe this force as "vapor pressure" It is often a very powerful force indeed. It can act independently of the flow of the air that holds the moisture. Vapor pressure can force moisture easily through wood, plaster, brick, cement ... right through most of the materials we use to build our homes. That's exactly what happens when moisture seeks to escape from the humid air usually found inside your home to the drier winter air outside. More Moisture Trapped in Less Space certain building materials stop water vapor. Glass is one of these. Also on the list are some varnishes, paints, tiles, plastic wall coverings, Vapor-seal insulation is designed specifically to stop the escape of water vapor and protect the insulation and your walls from the ravages of water.

Increased use of these "moisture trapping" materials in the last few years has created the modern "tight" home. Moisture created by bathrooms, kitchens, laundries and occupants no longer flow easily to the outside. The modern insulation and construction that keep cold air OUTSIDE also keep moisture in. So it is very easy to build up excessive and even harmful moisture levels in such homes. AMERICAN BUILDER magazine calls the problem a combination of many causes that build excessive moisture in the modern home. First, more washing, more bathing, more showers, more appliances, more gas furnaces - all pour more water vapor into homes than in former years.

HEATING AND VENTILATIONmagazine provides builders with reference data on sources of water vapor. For instance, cooking for a family of four adds 4.5 pounds of moisture a day to a house. Each shower contributes half a pound; a weekly laundry, 30 pounds; human occupancy contributes 6 to 3 pounds per day; dish washing 1.2 pounds, etc.

All of this moisture MUST eventually escape from your home. So you see that the modern living of a family of four can easily release 150 pounds, or more than 18 gallons of water per week into the air in your home! House's with no basements have further moisture problems. Now increased production of humidity is only part of the story.

Houses generally have been growing smaller and this means an even greater concentration of water vapor which is trapped by modern "tight" construction. It means MORE moisture contained in LESS space. No wonder we've created a condensation problem for ourselves!

David Bareuther, Associated Press Building editor, sums up the problem of reducing humidity this way. He says there are only three ways to reduce humidity:

• 1. CONTROLLING SOURCES OF HUMIDITY: For instance, venting gas burners, clothes dryers, etc, to the outdoors. Use of kitchen or bathroom exhaust fans.
• 2. WINTER VENTILATION: Because outside air usually contains less water vapor, it will "dilute" the humidity of inside air. This takes place automatically in older houses through constant infiltration of outside air.
• 3. HEAT: The process of heating our home will reduce the relative humidity - providing it's DRY HEAT. It will counterbalance most or all the moisture produced by modern living. Now, before we summarize specific steps for reducing humidity in your home, let's include some basic data about RECOMMENDED MOISTURE. You can refer to it if you are inclined to test the moisture levels in your home. The table below is the result of long and careful experiments at the University of Minnesota Engineering Laboratories. It shows the maximum safe humidity's for your home ... not just for the windows. Even MORE for your paint, insulation and structural members. In most cases, reducing moisture to these humidity's will cure troublesome condensation on window. If not, you can reduce humidity further without discomfort to you or your family. If you test humidity in your home, be sure to use an accurate instrument, preferably a good sling psychrometer. Remember, too, that these relative humidity's are for 70 degrees F. For higher temperatures, lower humidity's are required.

• These humidity's are comfortable. They are about the average of humidity's you would expect to find in a spring month in Phoenix, Arizona. Here, arranged from easy to more difficult, are the steps you should take to reduce condensation on you windows.

1. Put on storm windows or double-glazing.
2. Shut off furnace humidifier and any other humidifying devices in your home.
3. Be sure that louvers in attic or basement crawl spaces are open and that they are large enough.
4. Run kitchen or other ventilating fans longer and more often than has been you custom.
5. Open fireplace damper to allow easier escape for moisture.
6. Air out your house a few minutes each day. Air out kitchen, laundry and bathrooms during use or just following use.
7.  If troublesome condensation persists, see your heating contractor about outside air intake for your furnace; about venting of gas burning heaters and appliances, or about installation of ventilation fans. If the commoner remedies we suggest (number 1 through 5) don't work, you REALLY have a condensation problem. The changes your heating contractor may recommend, to further reduce humidity in your home, should not be very expensive. Certainly they will be less expensive than a big paint job caused by excessive water vapor!

• You see, the basic principle of reducing window condensation is extremely simple. When there's too much condensation on your windows, it means that humidity is too high in your home, You should take steps to reduce humidity until condensation disappears. In practice, window condensation and reducing humidity may become very complicated, because a score or more of entirely different conditions may affect the way the condensation problem works out in different homes. Let us just mention a few:

• The number and type of windows in the home
• The type of double glazing system used in the windows
• The heating system -- Hot air or water perimeter or interior wall heating.
• The type of insulation and vapor barrier
• Type of soil and quality of drainage

Because of so many variables, a condensation problem can sometimes be very tough to solve. That's why we recommend that you put an expert to work on your problem if the simpler steps to reduce humidity doesn't solve your condensation problems. See your architect or your heating contractor first. If they can't help, we suggest that you ask tour general contractor or lumber dealer to put you in touch with a qualified expert. They are available both at engineering schools and from the staffs of heating, insulation, wallboard or window manufacturer. Before we leave the subject of reducing humidity, we would like to add the following:

There are two causes of condensation that are TEMPORARY. They will disappear after a few weeks or at most a season of heating. First, there is the moisture that comes from new construction or remodeling. There's much moisture in the wood, or the plaster or the other building materials of a new home. When the heating season starts, this moisture will gradually flow out into the air in the home. Then it will disappear and not cause any more trouble.

Much the same sort of thing happens in a milder form, at the beginning of each heating season. During the summer, your house has absorbed some moisture. After the first few weeks of heating, your house will be dried out, and you'll hove less trouble with condensation. While we have been discussing the control of condensation we've mentioned just about everything EXCEPT windows. There's good reason. There is nothing much that can be done with WINDOWS to cut down condensation.

As the building experts have often pointed out, the windows are not to blame for condensation. In the moisture content of the inside air, lies both the cause and cure.

Construction materials in new homes are required to be water base products. This would include paint and caulking compounds. As all of these products dry or cure, this moisture is combined with the normal moisture that your household normally produces.