Indoor Condensation

The installation of your new Thermal Industries Vinyl Windows has made your home more air-tight and energy efficient. Over the years, you will save considerable energy dollars and enjoy a more comfortable living environment as a result of your investment.

Now that your house is more air-tight, moisture created by everyday activities (cooking, bathing, laundry, etc.) is no longer escaping through the drafty holes and cracks of your old windows. This moisture, now trapped in your home, looks for a place to rest/collect. Most often this moisture or "condensation" collects on your windows. It is important to understand that windows do not cause condensation, they simply reflect a condition in the home. Condensation is an indication of too much moisture in the air which manifests itself on the glass surface in three ways; (1) fogging, (2) droplets, (3) ice.

A little condensation is quite normal, and moisture can add to the comfort of an extremely dry home. However, excessive condensation can cause damage to paint, wallpaper and plaster if not controlled. The good news is, condensation can be controlled by reducing the sources of humidity within your home to an acceptable level of comfort.

Outdoor Condensation

During the spring, summer and fall seasons, when warm days are followed by cool nights, moisture may collect on the outside pane of glass on your windows. This collection of droplets is called dew, and is the same type of condensation you may see on your car windshield or lawn in the morning.

Insulating glass units utilizing high-performance glass systems, such as Peak and Super Peak Performance^™ Glass from Thermal Industries, are designed to reduce the amount of heat that flows from the inside of your home, to the outside of your home, during colder weather. By keeping more heat inside your home, the outside surface of the insulating glass unit stays colder. When the glass surface of your windows falls below the dew point (that's when water vapor in the air begins to condense), condensation forms on the outside glass surface.

Therefore, if you see condensation on the outside of your windows, this is visible evidence that your energy is being saved, and that your window investment is paying off.

Helpful Hints to Control Condensation*

• Shut off furnace humidifier and any other humidifying device in your home until condensation subsides.


• Be sure that louvers in the attic or basement crawl spaces are open and that they are large enough to allow adequate air flow.


• Run kitchen or other ventilating fans while cooking.


• Run exhaust fans while showering and keep bathroom door closed.


• Do not hang full loads of wet laundry inside your home to dry during the heating season.


• Vent clothes dryer to the outdoors.


• Open fireplace damper.


• Open a window and air out your house for a few minutes each day.


• If troublesome condensation persists, see your heating contractor about an outside air intake for your furnace.

*University of Minnesota Engineering Laboratory

NOTE: Condensation on glass is a natural result of excess moisture in the house and does not indicate a defective product or faulty installation. Maintaining proper household humidity levels may prevent problems such as mold, mildew and related health issues. In no event shall Thermal Industries, Inc. be liable for any damages including special, incidental or consequential damages resulting from condensation, mold or mildew. If you become aware of persistent condensation on your windows, you should take immediate remedial action to prevent water, mold and/or mildew damage to your property and to avoid potential health risks. Additional information is available upon request.

Back to Top