Window Condensation in the Winter and What To Do About it

Window Condensation in the Winter and What To Do About it

Why does condensation accumulate on windows and sills in the winter?

The answer stems from indoor humidity levels and temperature. Cold air does not have the ability to hold moisture as well as warm air. In addition, there is always moisture in the home. When this moisture cannot escape, it makes contact with the cold window surface… Now you have a perfect scenario for creating condensation.

Consider this example: When you take a can of pop out of the fridge and place it on the table, you’ll quickly notice water droplets on the outside of the can. (Condensation) The principle is the same, except we are talking about windows.

Other contributing factors include vapor diffusion throughout the home from wet building materials, poor balance of ventilation systems, improper use of exhaust fans in the bathrooms and kitchen, wet items left in the home and, believe it or not… people breathing.

If you are concerned that you may have high humidity levels in your home, you can purchase a hygrometer to measure moisture levels. For our environment in the Vancouver area, a good level to maintain is 55%.

Condensation is especially problematic with single pane, metal framed windows, most commonly found in older homes. When left unchecked, these older window assemblies will result in moisture damage, creating wood rot and mold growth to the window sills and corners. Newer, homes with tight building envelopes experience problems as well when metal framed windows have been installed. Be mindful however, windows are not the cause of condensation, high indoor humidity is the problem.

So how do we solve this problem?  The best way is to reduce indoor moisture levels by…

  •  Removing condensation from windows. On cold mornings, you’ll see a build up of moisture, or in some cases, frost. Simply take a cloth and wipe it away.
  •  Using proper ventilation when you cook, shower, wash clothing & dishes. All of these activities contribute to considerable moisture levels within your home. So it is always a good idea to keep the bathroom exhaust fan on before, while and after a hot bath or shower for a period of at least 20 minutes. Ensure that the fan is in good working condition and pulling enough CFMs (cubic feet per minute). In the kitchen, it is necessary to have a working fan that vents outside. Recalculating fans do noting to solve your indoor moisture issues.
  •  Maintaining a warm dry indoor temperature. When the temperature is warmer, less condensation will occur.
  •  Moving plants away from windows. Plants release a lot of moisture, so it is best to keep them away from the windows.
  •  Opening windows daily, for short periods of time. The introduction of fresh air into the home will help dilute and allow some of the moist air to escape. If you have the budget, install an HRV (Heat Recovery Ventilation) system.
  •  Servicing your furnace or boiler. The proper heat distribution balance and air intake for these combustion appliances can affect indoor moisture levels.
  •  Venting all large appliances outside. Laundry machines need to have all of the warm moist air to exhaust outside. So check the laundry connection points to ensure that they are properly installed and venting outside, not in the walls or attic.
  •  Installing double/triple pane, low E, vinyl windows. If you have double pane windows that have lost their seals, or there is significant damage in and around the window frame, then I suggest replacement.  Vinyl frame windows do not fluctuate in temperature as metal does. Note- Replacing your windows is expensive, so don’t run out and buy new windows without addressing the indoor environmental factors first.

When it comes to maintaining the window sills, be sure to monitor them often, keep them clean and paint only in the summer when the weather is dry.

To learn more about this topic or other issues relating to the home, call me at 604-729-4261 or send an email.