Household condensation, or “sweating”, on windows is typically caused by excess humidity or water vapor within the home. When water vapor in the air comes in contact with a cold surface, such as a mirror or glass window, it turns to water droplets — commonly called condensation. All homes have occasional condensation, often showing as fogging on the windows. This should be no cause for concern. 

However, excessive window condensation, frost, peeling paint, or moisture spots on ceilings and walls can be signs of excessive condensation. These warning signs should be taken seriously as they can be potentially damaging to your home. 

We typically notice condensation on windows and mirrors first because moisture doesn't penetrate these surfaces quickly. These surfaces are not typically the problem, however. They simply show the warning signs – indicators that you need to reduce the indoor humidity of your home. 

Household condensation can be difficult to solve – and there are many factors that affect condensation: the number and type of windows in your home, the heating system used in your home (hot air or water), the type of insulation and vapor barrier in the walls of your home, and even the type of soil and quality of drainage surrounding your home.

Are you wondering why your new “energy-efficient” replacement windows often show more condensation than your old windows that were typically draftier? The common answer is that your old windows allowed humidity to escape. Your new windows create a much tighter seal, so the extra moisture in your home is unable to escape, which makes you more aware of excess humidity. 

This is how we can say that windows do not cause condensation. Rather, they prevent humidity from escaping and provide an easy surface for condensation to collect.

All air contains a certain amount of moisture, even indoor air. Many household items generate indoor humidity such as your heating system, humidifiers, cooking devices, showers and baths, and more. In fact, every activity that involves water – yes, even mopping the floors counts – can contribute moisture to the air. 

Condensation is much more likely to occur in homes where January temperatures typically drop below 35oF because there are greater temperature extremes affecting the glass in the home. 

Additionally, it is very normal to experience condensation at the start of each heating season. During humid summer months, your home absorbs moisture and then “sweats” when you turn on the heat. This is no cause for concern – it is only temporary. After the first few weeks of heating, your home should be dried out, and condensation reduced or eliminated. 

If you have recently had some remodeling or construction complete, you may notice a similar thing. Due to the high levels of moisture in wood, plaster, and other building materials, your home may temporarily sweat during the first few weeks of the heating season. 

Another factor in condensation is technology. With today's modern insulation, moisture-barrier materials, and air-tight home construction, energy-efficient homes are possible. These homes, however, effectively keep the cold out, but trap moisture in the home, producing higher humidity levels and more condensation.

The best way to reduce condensation in your home is by eliminating excess humidity. 

Studies have shown that relative humidity ranges between 30% and 70% can be considered “comfortable”, depending upon a person's activity. 

However, for indoor air quality, upper ranges should be maintained below 50%, as the population of dust mites in a home increases rapidly at humidity levels above 50%. Additionally, fungal amplification occurs at relative humidity levels above 65%. So be careful with indoor humidity adjustments! 

We recommend buying a Hygrometer to keep track of your indoor humidity levels. These instruments are inexpensive and can be purchased online or in hardware stores. You'll find this to be an indispensable device to properly managing your indoor humidity.

The following chart illustrates recommended comfort levels of humidity during winter months:
 
Outside Temperature / Inside Relative Humidity




 
 
Indoor humidity can be measured with a humidistat or psychrometer. 
By eliminating excess humidity in your home, you can eliminate many condensation problems.

-20°F
-10°F
   0°F
+10°F
+20°F
+30°F
+40°F

15 To 20%
15 To 20%
20 To 25%
25 To 30%
30 To 35%
35 To 40%
40 To 45%

Ensure all ventilation to the outside is fully functional and unblocked. Use kitchen, bathroom, and laundry room exhaust fans during and after humidity-producing activities to release moisture.

Air your home periodically. Opening windows for just a few minutes each day lets stale, moist air escape and fresh, dry air enter without compromising your heating. Check your humidifier settings. Use recommended humidity comfort levels to correctly set and balance the humidity in your home.

Be sure all louvers in the attic or basement are open and are large enough and unblocked. Optionally, you may choose to open your fireplace damper to allow excess moisture to escape.

If you have many house plants, locate them in one area – and watch overwatering.

If troublesome condensation persists, contact a heating specialist about an outside air intake for your furnace, venting of gas burning heaters and appliances, or installation of ventilating fans.

Similar situations that cause condensation on the interior of a window can also cause condensation on the exterior.

The following are typical reasons for exterior condensation on your window: 
High relative humidity in the outside air
Calm air
A clear night sky 
The glass temperature is below the dew point temperature
Well insulated glazing
 
When exposed to the above-mentioned conditions, the exterior surface of glass will cool, causing the glass temperature to fall below the dew point of the ambient air. When this occurs, moisture from the air condenses on the glass surface. Only when the glass temperature rises above the dew point will condensation evaporate back into the air. Dew on grass, car hoods, and building roofs is a good determinant – and quite common. 

The presence of moisture indicates that the coordinated set of atmospheric conditions exists and that the insulating glass is properly doing its job – insulating the building from the outside air. In this case, the insulation capability is what retards the flow of building heat through the glass, and prevents warming of the exterior above the dew point.

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Whether you're shopping for windows and doors, roofing and siding, glass block windows,skylights, or seamless gutters, you'll find the quality products you've been looking for at Terry's Discount Windows and more – FOR LESS! 

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We serve clients throughout Porter County, Indiana, as well as Lake, LaPorte, Starke, Jasper and Newton Counties in Indiana.