Interior Condensation

Interior Condensation

Surface Condensation

Each person has his or her own preference regarding the humidity level in his or her home. If the occupants insist on a high level of humidity within the house, surface condensation must be expected when outside temperatures are low. Some indications of surface condensation are:

• Frost on door handles and hinges, or door frozen shut
• Water or ice on windows
• Damp spots on walls and ceiling
• Damp spots on closet walls
• Moisture on light fixtures
• Moisture on water closets
• Moisture on cold water pipes, walls and floors.

Some humidity is necessary for comfort and health. In many homes, it is a struggle to keep enough moisture inside the home to maintain an acceptable humidity level for the occupants. Frequently, humidifiers are installed to add moisture to the air, but their use must be controlled or surface condensation problems may result. Unfortunately, a dry house may indicate a high leakage rate (depending on the amount of moisture added by the homeowner), which can contribute to concealed condensation.

In some newer homes, however, air leakage is controlled so well that removing moisture from the house becomes a problem. This problem is made worse by the use of humidifiers, resulting in condensation on windows, mold growth, or damp spots on ceilings and room-side surfaces of exterior walls.

Because windows do not provide much resistance to heat loss, they are often the coldest component of a building enclosure, and can be an indicator of humidity problems. Because condensation occurs on inside window surfaces whenever the surface temperature falls below the dew point temperature of the room air, window condensation may signal a need to reduce the humidity level in your home.

What Can Affect the Performance of Windows?

(The following may cause condensation to form on a window)

Air Circulation - a window may be in an area in which there is poor circulation of warm air. This means that the temperature of the inside glass surface is colder than in other parts of the home and this may cause condensation to form at humidity levels which are practical for the rest of the home.

Drapes - based on natural circulation of warm air on the inside surface of the window. By drawing heavy drapes or venetian blinds over a window or patio door the possibility of condensation can be increased because the flow of warm air is restricted.

Varying Humidity Levels - remember that the humidity in some rooms, kitchens and bathrooms in particular, can be higher than in other areas of the home, thus encouraging condensation to form on the windows in these rooms.

Orientation - if windows are exposed to prevailing winds, then they will be slightly colder than the other windows in the home and may cause condensation to form at humidity levels which are practical for the rest of the home.

Exposure - some windows in the home may be protected by other buildings, trees, etc., which form a windbreak while others are totally exposed to the wind and, therefore, colder.

Exterior Condensation

With high performance glazing it is possible, under certain conditions, to have condensation on the outside of the glazing. The glazing radiates to the sky and on a clear night that can reduce the temperature of the outside surface to below the dew point. Condensation will form similarly to the condensation on a car windshield and, once the sun comes up, the condensation will disappear.

The phenomenon is only possible when the glazing unit high performance and little heat is being transmitted to the outer surface. It is not likely to occur on a cloudy night.