Worried about window condensation?


All air contains humidity, and in your home, especially in winter months, you tend to notice that there is more humidity on the inside of your windows.

It’s often referred to as sweating.

Indoor humidity can result from everyday activities such as showers, cooking, your furnace and even mopping your floors… it’s very common. When water vapour comes in contact with a cold surface like a mirror or window, the vapour turns into water droplets called condensation.

So why do your new energy-efficient windows show more condensation than the old ones? It’s simple. Your old windows were not air-tight and allowed heat and humidity to escape, but your new windows come with a tighter seal and the extra moisture in your home is now not able to escape.

But don’t worry. After a few weeks of heating, your home should dry out – reducing if not eliminating condensation.

The table below shows the recommended or comfortable levels of indoor humidity during the winter months.


-20˚F                                                   15% – 20%

-10˚F                                                   15% – 20%

0˚F                                                    20% – 25%

10˚F                                                    25% – 30%

20˚F                                                    30% – 35%

(Indoor humidity can be measured with a humidistat or psychrometer.)

Here are a few ways you can help reduce humidity in your home:

  • Use kitchen, bathroom and laundry room exhaust fans after humidity-producing activities
  • Air out your home periodically, it helps get rid of stale, moist air
  • Adjust your humidifier to the recommended setting for your home
  • Make sure air circulation is adequate in your basement and attic
  • If troublesome condensation continues, see your heating contractor