Windows and Condensation
Condensation is the transformation of water vapor into a drop of liquid. It occurs when warm air, with a greater capacity for holding moisture, comes in contact with a cold surface. The moisture that appears on the cold surface had been held in its gaseous state until it became chilled by "brushing" past the cold surface. A classic example is a glass of ice water. The glass is dry on the exterior when it is removed from the cupboard, but place a few ice cubes in it and fill it with tap water and see how quickly the glass becomes damp to the touch. The glass is not leaking or defective and the water you feel on the glass is not the water from the tap. Instead, it is water that moments earlier was part of the air we breathe.
In our homes, the coldest wall surface is always the window. Improvements in window technology have produced more thermally efficient products, yet in spite of these advances the window is still going to be colder than the adjacent wall surface. The window surface will be the first area to reach the dew point, the temperature at which the air can no longer hold water molecules as a gas. Much like the formation of fog outdoors in winter months, the combination of relative humidity and temperature make water vapor visible.
The presence of condensation moisture around window frames is not an indication of a faulty window. The window is acting as an indicator of relatively high humidity. We need to maintain a certain amount of humidity in our homes for personal comfort and even at moderate levels of relative humidity there are few noticeable indicators. The presence of high humidity is typically a result of multiple factors. Today's new home has been designed to achieve a higher level of energy efficiency and as a result the new home is less drafty than older homes. Homeowner personal habits contribute significantly to humidity levels in a home designed to minimize heat loss. Here are some tips to reduce condensation.
Circulate indoor air. Open a window. Use ceiling fans, especially
in rooms with less traffic such as a rear bedroom with adjoining bath.
Use laundry room and bath ventilation fans.
Ventilate the kitchen when boiling water or cooking. The steam rising from the pot is adding moisture to the air. Remember that moisture is a by-product of gas combustion and gas ranges produce moisture through normal use.