Frost in the Attic

By Mark J. Donovan

This year when you go up into the attic to get the Christmas decorations take a look around the attic to see if there is any frost on the roof ceiling or rafters. If there is then you have a moisture problem that should be taken care of. Moisture in the attic could lead to mold and mildew growth in the attic.

Observing frost in the attic is a sign that warm moist water is infiltrating the attic. Once the warm moist air hits the cold roof surfaces it freezes and forms the frost.

One of the leading culprits for warm moisture working its way into your attic is your bathroom ceiling fans. Check to make sure the bathroom ceiling fan vents and vent pipes are properly connected and that the vent pipes are directed outside the house. On several occasions I have discovered bathroom ceiling fans directly exhausting to the attic. The moisture with those hot steamy showers is captured in the cold attic and forms frost.

Another leading culprit for warm moisture entering your attic is simply poor insulation. Examine the insulation in the attic and make sure there are no openings in the insulation to allow warm air to rise into the cold attic. When warm moist air and cold air, come in contact with one another, condensation forms. When the attic air temperature falls below 32 degrees, the condensation freezes and forms frost in the attic.

Finally, if your house has a chimney check to make sure there are no signs of water infiltration around it. It is best to check for this after a good rain storm. Examine the chimney in the attic and look for streams of water or dampness around the bricks. If there are signs of water on the chimney then you need to apply a sealant or water repellant to the outside of the chimney. You may also need to re-install the flashing around the chimney.