Condensation on interior windows - is this a problem?

When I wake up in the morning, I’ve noticed that my bedroom windows are fogged, like mirrors in the bathroom after a shower. Is this a sign that I need new windows?

Check your weep holes.

Not necessarily, if the condensation is on the inside surface of the window (meaning you can wipe it of as you would the bathroom mirror). There can be several things causing this:

  1. you have poor quality windows that require replacement.
  2. you have already replaced your windows with a quality replacement window, yet you have heavy draperies and/or blinds that are not allowing adequate air circulation on the glass surface. This will allow moisture in the air to condense on that cool surface.

Do you notice the condensation only when it is cold outside and the condensation is only on the inside, not between the glass panels in a double pane window? If this is the case you may have too much humidity inside your home and as the window cools from cold temperatures outside the moisture condenses on the window. Check your furnace and see if you have a humidifier set too high. You can also check your humidity. In the heating season it is good to keep it around 45%. A dehumidifier can also help reduce humidity if it is too high.