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Lack of Air Movement
Without air movement, evaporation is almost impossible. Think of a hot,
humid summer day when there isn't a gently breeze. Now, take that same
day and add a gently breeze. The thermometer may read the same, but
because of the airflow, it doesn't seem as hot. Why, because of
evaporation. Evaporation occurs when there is an increased disturbance
between water and air. After a heavy rain, it may take two or three days
for a puddle of water to evaporate. However, if that same puddle
is spread out, it can evaporate in a matter of hours. The more surface
area of the water is exposed to air currents, the faster evaporation
occurs. When you take a shower and do not turn on the exhaust fan, your
mirror clouds over with condensation.
However, if you
turn on the exhaust fan, the amount of condensation is less. So, what
does evaporation have to do with windows?
Condensation occurs on a surface because when there is a lack of air
current no energy is provided for water to revert in vapor. A strange
thing sometimes occurs when replacing old windows with new, energy
efficient windows, more condensation occurs. Why? You've just invested a
lot of money and your windows have condensation. This can be a good
thing. How, you ask. With your old windows, the inside of your home had
favorable conditions for condensation, but because your old windows
permitted draft to occur, the constant airflow evaporated any
condensation. However, your drafty windows also increased your heating
bill. Your new energy efficient windows don't permit heat to escape, so
the moisture in the air settles condenses on your windows as
condensation. Your energy efficient home has less heat loss and a
better balance of inside humidity and temperature.
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