Window Condensation

By Ron Dalton, R.C.M., A.I.H.M.
From the WB Condo Connection – Volume 2, Issue 3
It has come to our attention that many people experience problems with condensation on their windows and balcony doors during the heating season and, in some cases, the moisture is damaging the walls and floors. To assist in eliminating all or most of this problem we recommend the following parameters for your health and comfort:

• Set your thermostat to keep the temperature at or near 20 degrees C (68 degrees F). Warm air holds more moisture than cool air. When warm air with 60% relative humidity at 25C is cooled to 20C, the relative humidity increases to 80%. Cooling the same air to 17C causes it to reach the dew point (saturation point). Further cooling when this same air is exposed to a cold surface (i.e. windows) causes some of the moisture in the air to condense; that is, some of the moisture in the air will become water.

• During cold weather, the relative humidity should be 30 to 55%. (35 to 40% is usually comfortable for most).

• Use your kitchen and bathroom ventilation fans when cooking, showering/bathing etc. Apartments require a 5 liter per second (10cfm) minimum ventilation rate during the winter.

• Try to keep good air circulation and distribution to all rooms. It will help if you open your windows slightly when the outside temperatures permit.

There are many sources of moisture in your apartment, some of which are: house plants, dryers, washers, dishwashers, cooking and boiling water, bathing and showering, floor washing, furniture and people. Furniture absorbs moisture in the summer during times of high humidity and releases the moisture in the winter. Each person produces about 1.25 liters of moisture per day by respiration.
If water condenses and collects on doorsills and windowsills it is helpful to dry it as soon as possible as this water also becomes a source of moisture and humidity. Overflowing sills causes damage to walls, carpets and floors etc. It is also helpful to keep the drainage ducts in the doorsills and windowsills clean so that any accumulation of water will drain to the outside.
Additionally, in a high-rise building it is important that your entry door to your unit does not have weather stripping applied around the perimeter. The entry doors are designed with a gap to allow make-up air from the corridors to help with ventilation in your suite.