What is Condensation?

Condensation is the process of removing water from the air. Condensation occurs anytime moist warm air contacts a cold surface. For example, the beads of water that drip down a cold can of pop or glass of ice water are products of condensation. In the winter, the fog that forms inside your car windows before the defroster has a chance to work is also condensation from the moisture in your breath. In your home, condensation may appear as frost around the edges of your windows, caused by the moist air contacting the cold surface.

What is Problem Condensation?

Problem condensation is EXCESSIVE condensation. It is the kind that causes enough frost or fog to block whole windows. It causes water to run off the windows, staining woodwork and damaging wallpaper, sheetrock or plaster. If you have this kind of condensation on your windows, you have a good reason to worry. It's natural to blame your windows but you shouldn't. Windows don't cause problem condensation. They only warn you that you have it.

The Cause of Problem Condensation is EXCESS HUMIDITY Inside your Home.

It's the same as water vapor, too much water vapor. It may be freezing in the insulation in your attic where it will melt and damage your ceilings exactly like a roof leak when warm weather comes. It may be forcing its way out through siding to form blisters on exterior paint. That means the most expensive kind of paint job.

Humidity, water vapor, moisture, steam, call it what you will, they are all the same. They are all water in the form of invisible gas in the air. They can be present in varying quantities in the air.

Humidity can be a Powerful Force.

Moisture in wet air forces its way toward drier air and mixes with it. Scientists call this force vapor pressure. It is often a very powerful force. Vapor pressure can force moisture easily through wood, plaster, brick and cement. Vapor goes right through most of the materials that we use to build our homes. That is exactly what happens when moisture seeks to escape from the humid air inside your home to the drier winter air outside.

More Moisture Trapped in Less Space.

Some building materials stop water vapor. Glass is one of these. Also on this list are some varnished, paints, tiles and 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 devastation of water.

Increased use of these moisture trapping materials required by building codes and manufacturers, in the last few years has created the modern term tight home. Moisture created by bathrooms, kitchens, laundry rooms, and occupants, no longer flows easily to the outside as it used to in older homes. The modern insulation and construction that keeps cold air outside also keeps 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 of a combination of many causes that build excessive moisture in the modern home. More washing, more bathing, more showers, more appliances, more gas furnaces all pour more water vapor into homes now than in former years.

Heating and Ventilating magazine provides builders with reference data on sources of water vapor. For instance, based on a family of four, cooking adds 4 ½ pounds of moisture each day to a house. Each shower contributes ½ a pound a day; a weekly laundry, 30 pounds; human occupancy, 6 to 8 pounds. All of this moisture must eventually escape from your home. So you see that the modern lifestyle of a family of four can easily release 150 pounds, or more that 18 gallons of water per week into the air in your home! Houses with no basements have further moisture problems.

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.

A score or more of entirely different conditions may affect the way the condensation problem works out in different homes. Let's mention a few:

• Size of the home
• Ventilation of the house
• The heating system- hot air or water- perimeter or interior wall heating
• The type of insulation and vapor barrier
• Even the 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 first try any of the six humidity controlling steps listed in this article (Chart 1.1) before calling in outside help. Often, these simple steps will solve the problem and require minimal expense.

Temporary Condensation Problems

Before we leave the subject of what causes excessive condensation problems we would like to add the following information about temporary condensation. Two causes of condensation 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 is quite a lot of moisture in the wood, or the plaster or other building materials of a new home. When the new 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.

Mush of the same sort of thing happens in milder form at the beginning of each heating season. During the summer, your house absorbs some moisture. After the first few weeks of heating, your house will dry out and you will have less trouble with condensation.

While we have been discussing the causes of condensation, we have mentioned just about everything except windows. There is a good reason. There just 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 the cure.

1.1 Six practical steps to controlling condensation and excess humidity

1. Replace old worn out windows with insulated glass. This will better insulate your windows from the outside cold air. Remember, moist air must contact a cold surface in order to condense. By installing windows that maintain a warmer indoor surface you will minimize the amount of moist air but it will make looking out your windows easier.
2. Be sure that louvers in the attic or basement crawl spaces are open and they are large enough for your attic space. You can refer to your local building code or contractor for a chart on how much exhaust you need for your home.
3. Run your kitchen or other ventilating fans longer and more often than has been your custom. This will help release the condensation that has built up.
4. Shut off your furnace humidifier and any other humidifying devices in your home. The process of heating your home will reduce the relative humidity providing its dry heat. This alone will counterbalance most or all of the moisture produced by modern living.
5. Open your fireplace damper to allow easier escape for moisture.
6. A dehumidifier can help reduce interior condensation. If you don't have a dehumidifier, air out your house for a few minutes each day. Air out your kitchen, laundry, and bathrooms during use or just following their use.

If these common remedies don't work, the condensation problem should be looked at by a heating or ventilation contractor. They may suggest an outside air intake for your furnace, venting a gas burning heaters and appliances, or the installation of new ventilating fans or roof/ soffit vents. These inexpensive options will be less costly than a major painting job or plaster work caused by excess water vapor.

The Basic Principal of Reducing Condensation is Extremely Simple.

Where there is too much condensation on your windows, it means that humidity is too high in your home. You should take necessary steps to reduce humidity until condensation disappears.

Following is some basic data about recommended indoor moisture levels. You can refer to it if you are inclined to test the moisture levels in your own 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 for your home not just for your windows. These levels are even more important for your paint, insulation and structural members.

In most cases, reducing moisture to these levels will cure troublesome condensation on windows and will cause no dryness discomfort to you and your family.

If you test humidity in your home, be sure to use an accurate instrument, preferable a good sling psychrometer. Remember too, that these relative humidity levels are for 70 degrees fairenheight. For higher temperatures, lower humidity levels are required.

Outside Air Temperature	Inside relative humidity for 70 degree F. Indoor air temperature.
-20 degrees F or below	Not over 15%
-20 degrees F to -10	Not over 20%
-10 degrees F to 0	Not over 25%
0 degrees F to 10	Not over 30%
10 degrees F to 20	Not over 35%
20 degrees F to 40	Not over 40%

These humidity levels are comfortable. They are about the average humidity levels you would expect in a spring month in Phoenix, Arizona.

References:
Soft-Lite Windows LLC, 1998