Guide to Common Household Condensation


Common household condensation or “sweating” on windows is caused by excess humidity or water vapor in a home. When water vapor in the air comes in contact with a cold surface such as a mirror or glass window, it turns into water droplets called condensation. All homes have occasional condensation, such as a little fogging on the windows, but this is no cause for concern. On the other hand, excessive window condensation, frost, peeling paint, even moisture spots on ceilings and walls can be signs of excessive condensation and potentially damaging problems in your home. We tend to notice condensation on windows and mirrors first because moisture doesn’t penetrate these surfaces. Yet they are not the problem, simply the indicators that you need to reduce the indoor humidity of your home.


You may be wondering why your new energy-efficient replacement windows show more condensation than your old drafty ones. It’s simple—your old windows were not airtight and allowed humidity to escape. Now that your new windows create a tighter seal, the extra moisture in your home is unable to escape, therefore making you more aware of excess humidity. Windows do not cause condensation; instead they prevent humidity from escaping and provide an easy surface for condensation to collect.


All air contains a certain amount of moisture, even indoors. Indoor humidity is generated by many household items and activities, such as your heating system, humidifiers, cooking and showers. In fact, every activity that involves water, even mopping the floors, contributes moisture to the air.

Climate can also contribute to condensation. Condensation is more likely to occur in homes where January temperatures drop below 35°F because there are greater temperature extremes affecting the glass in the home.

It is typical to experience condensation at the start of each heating season. During the humid summer months your home absorbs moisture and then perspires when you turn on the heat. This is only temporary though; after the first few weeks of heating your home should dry out—reducing, if not eliminating, condensation.

You’ll notice the same scenario if you have done some remodeling or building. Due to the high levels of moisture in wood, plaster and other building materials, your home will temporarily sweat during the first few weeks
of the heating season.

Another factor in the condensation equation is progress. With today’s high-performance insulation, moisture-barrier materials and airtight construction, we all enjoy a more thermally efficient home—one that blocks the cold out, yet traps the moisture in, producing higher humidity levels and more condensation.


The best way to reduce condensation is by eliminating excessive humidity. The following table illustrates the recommended or comfortable levels of indoor humidity during the winter months.

-20°F                 15%
-10°F                 20%
0°F                  25%
10°F                 30%
20°F      35% – 40%
(Indoor humidity can be measured with
a humistat or psychrometer.)

By eliminating excessive humidity in your home, you may very well eliminate most, if not all, of your condensation problems.


  1. Make sure all sources of ventilation to the outside are functional, and use kitchen, bathroom and laundry room exhaust fans during and after humidity-producing activities to vent excess moisture.
  2. Air out your home periodically. Opening windows for just a few minutes a day lets the stale, moist air escape and the fresh, dry air enter without compromising your heating.
  3. Check your humidifier settings. Use the humidity comfort levels provided in the table to correctly set and balance the humidity level in your home.
  4. Be sure that all louvers in the attic or basement are open and large enough. You can even open your fireplace dampers to allow excess moisture to escape.
  5. If you have a large amount of houseplants, try to concentrate them in one area and avoid over-watering.
  6. If troublesome condensation persists, see your heating contractor about an outside air intake for your furnace, venting of gas burning heaters and appliances, or installation of ventilating fans.

How to care for vinyl replacement windows

Proper care for vinyl replacement windows

Today I’d like to share with you the proper ways to care for vinyl replacement windows.

The day of installation, we recommend that you refrain from opening or closing your new window for at least twenty-four hours to allow the caulk to properly set.  So please resist the temptation to open your brand new, beautiful windows until the next day.

During this time, you may have some remaining labels or tape adhesive still attached to the glass of your new replacement windows, we recommend removing these with any alcohol-based cleaner.  Once you’ve removed this residue, wet the glass and rinse with plain water.  Avoid washing the vinyl frame with alcohol-based and/or abrasive cleaning solutions.  Like any other window, use Windex or similar ammonia-based cleaning solutions on the glass portion of your window.

The vinyl (PVC) frame can be cleaned with a mild soap and water solution.  If the job requires more than just soap and water, use any non-abrasive household cleaner.  Your windows shouldn’t require more than that, using solvents, paint thinner or removers, or sharp objects is not recommended.

Replacing your old windows with new energy-efficient vinyl windows will tighten up your home.  If you experience an increased amount of condensation on the inside of your windows, it’s caused by an excess amount of moisture in your home.  Prior to the installation of your new windows, not only were you losing energy in the form of cold air from your air conditioning in the summer and warm air from your heating source in the winter, the lack of a proper seal allowed moisture to flow in and out of your home.  Having excess moisture in your home can result in the growth of mold, which can be potentially hazardous to your health.  By replacing your windows, you’ve prevented outside moisture from entering your home through the windows.  However, your windows will also prevent moisture from escaping, sometimes resulting in condensation on the inside of your windows.  It is your responsibility to control your home’s humidity.

If mildew is a problem in your area, use an appropriate cleaner or mildew controller.

The color of your vinyl windows is solid throughout all window components.  You should not paint or varnish your new windows, it will void your warranty.

The outside tracks of your double hung or slider windows are exposed to dirt, leaves, sand, grease, soot or other abrasive materials.  These materials can be ground into the vinyl tracks when you open and close your window sashes.  We recommend you clean the tracks every six months or as needed. You should clean these tracks with a small, stiff nylon brush, then wipe down with a soft cloth. If necessary, an occasional light coat of silicone spray lubricant on the balance shoe track of a double hung, and the tracks of a slider window, will help ease the operation of your window without leaving an oily residue which can collect more abrasive elements.

Always follow the manufacturer’s recommendations for safe use of any chemical or cleaner. Any cleaning information we suggested is only to assist you. We assume no responsibility for results obtained which are dependent on the chemical solutions as prepared, and quantity and method of application.

If you follow these tips on how to maintain and care for vinyl replacement windows, they’ll remain as beautiful as the day they were installed.