A phenomenon caused by prolonged cold spells and improper ventilation.
Attic cold in fall.
Adequate attic ventilation allows cool dry air from outside to come into the attic while warm moist air inside the attic can escape.
Attic flies common this winter by donald lewis department of entomology the large black pesky flies that show up in bed rooms and on window sills from late fall through early spring have been very abundant this year possibly because of the wetter than normal weather we had last summer.
Department of energy doe the average unimproved attic has just r 19 insulation the insulation value of a five and a half inch thick fiberglass batt.
During cold winter months the attic vent fan is not necessary.
Good attic ventilation helps keep temperatures even preventing hot and cold spots that cause damaging ice dams where water can back up and freeze beneath your shingles.
If your attic is too cold it probably lacks sufficient protection from outside temperatures.
The attic is the hottest part of the house in the summer and is cold in the winter hot air rises up to the attic cold falls drops into the living space moisture rises and accumulates in the attic central heating ac systems and ductwork are often in the attic.
The biggest issue is attic rain.