Facts about Condensation and Moisture

Condensation occurs when humidity is high and/or temperature is low. The important point to remember is “warm air has more ability to hold moisture than cold air”.

“Moisture” is water in all forms, including: vapor, liquid, ice, or frost. Air always contains some moisture in vapor form. The moisture vapor in outside air comes from evaporation of water from lakes, rivers, and oceans.

What is Relative Humidity?

Relative Humidity (RH) is the percentage of water vapor present in the air, relative to the maximum amount of moisture that the air can hold at that temperature.

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Cooling the air raises the humidity; and heating the air lowers the humidity, assuming moisture is not added or removed.

Prevention or Control of Moisture/Condensation

Prevention or control of moisture in the air may be accomplished by one or more of the following:

  • In the winter months, develop adequate ventilation in the attic, or install a dehumidistat control with a fan in the attic.
  • Install vapor barriers and retarders on the warm side walls, ceilings, and floors. Envelope the living space.
  • Increase insulation in the ceiling of the top floor living space.
  • Use double or triple glass and wood frame windows.
  • Install a dehumidifier in the basement during the summer.

Prevention of Low Humidity in the Winter

When cold air is brought inside and heated, it becomes dry.

  • Utilize a humidifier
  • Increase the insulation
  • Install vapor barriers and retarders on the warm side walls, ceilings and floors. Envelope the living space.

More Condensation Facts…

  • Condensation develops in the basement during the summer because the RH in the outside air is often high (60%-100%), and the basement areas are cooler than the outside temperature.
  • Condensation develops in attics when moisture vapors are not vented, and the lower temperatures cause them to turn liquid.