|During the winter months,
homeowners often encounter condensation on the windows in their homes. The
goal of this article is to define the problem, the causes, and the
solutions to this bothersome and ever present potential harm.
If you are troubled during the fall and
winter by condensation on the windows of your home, you aren't alone. It
is a common problem in cold climates. The typical family produces a lot of
moisture indoors (washing, showers, cooking, just breathing, etc.) and it
can be difficult to reduce it.
Understanding the causes of the problem
is the first step in solving it. Condensation and ice form on windows
because the window surface is below the dew point for the air near the
window, so some of the moisture in the air condenses on the glass. The
higher the relative humidity of the air near the window, the higher the
temperature of the dew point.
For example, if the thermostat is set at
20 C degrees, the temperatures on the surfaces of your windows will be
much lower, how much lower depends on the outside temperatures and the
insulating value of the window. When the outside temperatures are at the
freezing point, temperatures on the inside surface of a double glazed
window could easily be 10C degrees lower. As the temperature of the air
near these cold surfaces drops, its relative humidity climbs to the point
where condensation can occur. To eliminate condensation, homeowners either
need to raise the temperature of the window surface or reduce the relative
humidity in the room.
If the condensation occurs on the prime
window and the window is double-glazed, that usually means the relative
humidity is too high for the temperature conditions. With a thermostat set
at 20C degrees, condensation should not occur on double-glazed windows
until outside temperatures drop well below zero, if relative humidity is
kept below 40 percent. If you have additional glazing, including Low-e
coatings and argon gas filled spaces, it takes even colder temperatures
before condensation occurs.
Several conditions can increase
condensation problems. If you close drapes over windows, this can cause
the glass temperature and the temperature of the air between the drape and
the glass to become cooler, making condensation more likely. If the
thermostat setting is dropped substantially at night, this will cause an
increase in relative humidity and may increase condensation. This
condensation should vanish once the temperature rises in the morning.
The best way to deal with condensation
on high-quality, double-glazed windows is to reduce indoor relative
humidity to no more the 40 percent. The best method to control indoor
humidity is with ventilation. Run range hood, kitchen and bathroom vent
fans whenever you are using those rooms. The best solution is to install a
whole-house heat recovery ventilation system. These save heat from the
indoor air before it is exhausted outdoors and transfers this heat to the
incoming fresh dry air. These systems also improve indoor air quality
inside your home. The fans will be more effective if you open a window
elsewhere in the house to provide replacement air. Be sure that the fans
you use exhaust to the outside, instead of going to the attic or just
recirculating air within the house.