Q-Before I replaced my windows I had double pane aluminum windows. I would get condensation on the inside of my windows, now that I have new vinyl replacement windows I sometimes get condensation on the outside. Is there something wrong with my windows?
A- No Condensation on the outdoor surface of an insulating unit is not an indication that the vinyl replacement window is defective. Under the right set of atmospheric conditions it is possible to get condensation on the exterior glass of your vinyl replacement windows. Specifically, these conditions are as follows:
: Glass temperature below dew point temperature
: Clear night sky
: Still air
: High relative humidity
: Well insulate glazing
Exposed to these conditions, the exterior surface of the glass can radiate heat away to the night sky such that the glass temperature falls below the dew point of the ambient air. When this occurs, moisture from the air condenses on the glass surface. Only when the glass temperature rises above the dew point will the condensation evaporate back into the air. Dew formation on grass, cars, building roofs and walls, is a common and accepted as a fact of nature.
The presence of moisture indicates that the specific set of atmospheric conditions exist and that the glass in your new vinyl replacement window is indeed doing the job, that is insulating the building from the environment. In this case, that insulation capability is what retards the flow of your houses heat through the glass and prevents warming of the exterior above the dew point.