CONDENSATION
WHEN A LEAK ISN’T A LEAK!
 
CONDENSATION AND SKYLIGHTS

   Condensation is usually more noticeable on skylights because warm, moist air rises to the ceiling. The problem, however, usually isn’t the skylight. It’s the excess moisture in the room. Condensation is more prevalent in new homes. After a few years, new homes tend to dry out and have less moisture problems. Eliminating excess moisture by using a dehumidifier and providing adequate ventilation and air circulation will go a long way in preventing condensation.

UNDERSTANDING CONDENSATION

   Condensation is the conversion of vapor to liquid. It occurs when the air becomes saturated with moisture and releases it in the form of water. It is recognized by the wet mist that sometimes clouds the interior glass on your home’s windows.

   This may also be the first warning sign that your home is retaining too much moisture elsewhere. And even if your house doesn’t actually feel damp, that excess moisture could be doing damage in unseen places.

WHAT CAUSES THE EXCESS MOISTURE?
   The air around us contains water vapor (humidity), and we add more water vapor to it by normal breathing, perspiration, cooking, cleaning and showering. When the air becomes saturated with excess humidity, it dispels the moisture by condensing it back into water. This is what shows up on your window’s glass.
 
OUTSIDE AIR TEMP.
INSIDE HUMIDITY
-20° F or below
15 – 20%
-20° – -10°
20 – 25%
-10° – 0°
25 – 30%
0° – 10°
30 – 35%
10° – 20°
35 – 40%
Based on engineering studies at 70°F indoor air temperature.
    WHY DOES CONDENSATION OCCUR MAINLY IN THE WINTER?
   Condensation occurs more often during cooler weather because a greater temperature difference exists between the warm interior of your home and the colder outdoors.

   Warm air carries larger amounts of water than cold air. When warm, moisture-laden indoor air contacts a cool surface, such as a window pane, the moisture in the air forms condensation on that cooler surface.

The chart at left shows general guildlines inside humidity levels that should help to avoid condensation.

This information is provided solely as an aid to owners of VELUX Roof Windows and Skylights who may be experiencing condensation problems. VELUX America Inc. cannot, however, accept responsibility for these problems, the accuracy of any statement or the failure of remedial action.