Dealing with Jack Frost

Dealing with Jack Frost

Posted by:  Simon Paquette (Service Manager)

When condensation appears on your windows during the winter months, the immediate thought is that the window performance is inadequate or that the window has been installed improperly. In reality, the culprit is usually too much humidity. Interior surface moisture can appear on many different cool surfaces in your home, such as toilet tanks, cold water pipes, door hinges, and windows. The lower the level of humidity in your home, the less likely you will see this happen.

Below are a few tips on what to do should you experience this problem:

  1. Turn off your humidifier during the first winter. In new homes, considerable quantities of moisture may be released from various construction materials (ie: concrete, paint, lumber). This adds considerably to the total moisture load during the initial 18-24 months of occupancy but will dissipate over time.
  2. If you have a power humidifier see control panel for recommended humidity percentage vs. outside air temperature and adjust accordingly and keep a separate humidistat to monitor humidity levels.
  3. Change furnace filters frequently during winter to enable the furnace to circulate air as efficiently as possible
  4. Open windows periodically to allow dry outside air to replace moist inside air
  5. Always use bathroom fans when bathing or showering (leave fan running for approximately a half hour to clear fan vents of excess water) and hood fans while cooking.
  6. Avoid multiple daily temperature adjustments as this can have undesired effects on the humidity level
  7. Do not block hot or cold air vents, as this can affect air circulation
  8. Leave blinds or drapes open as wide as possible at night and open all window coverings during the day. This will increase the warm air circulation over the cool surface and increase the temperature of the glass

The table below shows the maximum recommended relative humidity for different outside temperatures. It shows that as outside air temperature drops, the relative humidity must also drop to minimize condensation. Improved ventilation will also assist in reducing the amount of condensation, by increasing the temperature of the cold surface.

Outside Air Temp (℃)
Desirable Maximum Inside Relative Humidity (%)
(at indoor temperature of 21 ℃)
-30℃ or below Not over 20%
-30℃ to -24℃ Not over 25%
-18℃ to -12℃ Not over 30%
-12℃ to -6℃ Not over 35%
-6℃ to 0℃ Not over 40%

NOTE: If you have hardwood floors, please refer to the manufacturer’s warranty for the required humidity level.


About the Author

Simon is quick to fix everything that needs fixing, but even quicker to whistle a happy tune.

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