Guide to Understanding Condensation - part II
Part I - November 2005 Featured Product - Windows and Condensation and Andersen® High-Performance Glass

CONTROLLING INDOOR HUMIDITY

Does the amount of condensation depend on the window type?
Bay or bow windows usually experience more condensation than other window styles. This is because inside air circulation around these window styles is usually more restricted. And, since they hang away from the insulated house wall, bays and bows are usually a few degrees cooler in temperature. To help control excessive condensation, it's smart to insulate between the window head and platform. In extremely cold climates, additional insulation above and below the window platform may be needed. as a secondary measure, placing a common electric fan near the window helps promote air circulation and can reduce window condensation.

How do drapes and window shades affect window condensation?
Drapes and other window coverings can contribute to a condensation problem by restricting the flow of warm room air over glass surface. Therefore, indoor condensation is more apt to occur when the drapes are closed or the shades are pulled down.

Why does a 1"-wide strip of condensation sometimes form all the way around the window?
If a strip of condensation forms all the way around the window, chances are good that the unit features metal components that are transmitting cold from the outside to the inner glass, cooling the glass surface where the condensation forms. In effect, the center of the glass stays warmer than the glass close to the edge. This strip of condensation doesn't mean the window is leaking air or not working properly.

What causes condensation on the inner surface of storm windows?
All operating windows leak some air between the window frame and sash. So when warm household air seeps in around the sash and becomes trapped by the colder storm window, condensation forms on the inside surface. Providing outside ventilation to the combination storm window can usually reduce condensation buildup.

What causes moisture to form on the outside of the windows?
It's dew, the same condensation you see on windshields. lawns and streets on many mornings. Condensation like this happens only when the exterior surface temperature of the glass falls below the dew point of the air. When humidity levels are higher, this kind of condensation is more likely to form. Most of the time, exterior window condensation takes place in the Spring and Fall, when cool nights follow warm days.

Can excess condensation damage windows?
Excess window condensation can cause paint to peel from the sash. Excess moisture can also damage the window frame.

Is exterior condensation anything to worry about?
Dew on windows is a natural atmospheric phenomenon, and it doesn't mean your windows are leaking air or malfunctioning in any way. In fact, exterior condensation is a sign of energy efficiency, since it means the outside pane is thoroughly insulated from the heat indoors. Depending on where you live, it may occur just a handful of times per season.

Are there any cases where window condensation in only temporary?
There are primarily three causes for temporary window condensation.

New Construction: Wood, plaster, cement and other building materials used in new construction and remodeling produce 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.
Heating Season: At the beginning of the heating season, there may be a certain amount of temporary condensation. During the humid summer months, your house can absorb some moisture. After the first few weeks of heating, this moisture should dissipate.
Preceding Temperature Shifts: Sharp, quick drops in temperature can also create temporary condensation problems during the heating  season.

Andersen® High-Performance™ Glass

What is the relationship between window performance and relative humidity?
 

What causes condensation between the panes of glass?
Condensation between two panes of glass in a multi-pane unit can be one of the most annoying condensation problems. It not only clouds the view, but can leave stains between the glass. It is also an indicator of an even more critical problem - seal failure. Window systems with two or more panes of glass, and especially those with low-emissivity coatings, rely on the integrity of the glass-to-glass seal to a) protect the Low-E coating b) help retain any specialty gases that may be in the unit c) ensure long-term energy efficiency. Such seal failures can be the result of a manufacturing defect. Depending on the warranty, the manufacturer should be contacted in order to replace the unit.

How does Andersen® High-Performance™ Low-E glass work?
It works through a special metallic coating bonded to the interior surface of the outside pane of glass. It's almost invisible, but this revolutionary coating actually detects radiant heat and restricts its flow through the glass. During cold weather, High-Performance™ glass keeps heat inside. In warm weather it keeps heat outside.

What is the difference between Andersen® High-Performance™ & High-Performance Sun™ glass?
Andersen High-Performance glass is generally used in climates with harsh winters. In the heating months, it is 35% more energy efficient than ordinary double-pane insulating glass. High-Performance Sun glass, on the other hand, is specifically designed for the hotter climates or homes with a full western or southern exposure. In the cooling months. Andersen High-Performance glass is 41% more energy efficient than ordinary double-pane glass.

You can learn more about Andersen® Windows or condensation by calling us or visiting www.andersenwindows.com.

"Andersen" and the AW logo are registered trademarks of Andersen Corporation

Information and specifications are subject to change without notice.
09/18/06

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