Condensation

What it is & where it comes from?

Sometimes people express concern about condensation – the fog or moisture that can appear on windows in the colder months.  This does not indicate a problem with either the construction or installation of the windows. Quite the contrary, it indicates that the windows and sealed units are performing well.  Aluminium frames are even more likely to cause condensation problems.  Basically, condensation occurs when humid air comes into contact with a surface that is cooler than the air itself. This happens most often in winter,

The humidity that leads to condensation is a normal product of everyday life. According to studies, a family of four can release up to twenty pounds of moisture that is the equivalent to two and a half gallons of water – into the air every day, just through the daily routines of cooking, showering, cleaning, and breathing. Therefore, the more activity in your home, the more likely you are to see condensation.  Other major contributors to household humidity include: humidifiers, water pans on radiators or wood stoves, kerosene heaters, drying laundry, and houseplants. The construction of the home – the kind and amount of ventilation, the presence or absence of a cellar – even the soil type and drainage patterns of the land on which it is built can add humidity as well.  In many cases, simply being aware of the sources can reduce humidity and reducing daily use – for example, boil less and bake more when cooking and take shorter showers.

Here’s what you can do to reduce the humidity that causes condensation.

Fan it out: when using bathrooms, kitchen, or laundry room, turn on any built-in fans.

Dry it Out: Use a dehumidifier to remove excessive moisture from the air.

Air it Out: Every day, open a door or window for a few minutes to air out the home.

Move it out: in cold weather, move houseplants to the sunroom or other seldom-used room.

Other methods exist, but may require professional advice.

Outdoor condensation

Condensation on the outdoor surface of an insulating unit is not and indication that the glass or insulating unit is defective. Under the right set of atmospheric conditions it is possible to get condensation on the exterior glass surface of an insulating glass unit.

Exposed to certain atmospheric conditions, the exterior surface of the glass can radiate heat away to the night sky such that the glass temperature falls below the dew point of 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 the condensation evaporate back into the air. Just like the dew formation on grass, cars and outside furniture it is common and accepted as a fact of nature.

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

If exterior condensation occurs on insulating glass, there is little or nothing that can be done to prevent its reoccurrence. Draperies should be open to allow as much heat transfer through the glass as possible. Trees or buildings can block the radiation view to the sky. Shrubbery immediately adjacent to the glass can increase local humidity and may need to be moved. The exterior surface of the glass will warm and the condensation will evaporate when the heat loss to the sky is blocked (i.e. clouds), the wind picks up, or sunlight is absorbed on the glass surface.