Winter Dampness

Posted by in Attic Ventilation, Buying/Maintaining a Home, Winter Concerns | February 24, 2014

Frost on protruding nail shanks and underside of roof deck.

 

In our last blog we discussed the potential effects of the excessive dryness in homes this winter (2013-2014) in Northeast Ohio.  But as dry as the interior has been there is also an increase in damage from the increased condensation of excessive airborne moisture on the framing in the attic.  That is, as the framing has been chilled more than usual by prolonged temperatures below 15° F, the airborne moisture in the attic has been condensing out on the cold surfaces just as it does on a cold glass of lemonade in the summertime.

These two contrasting phenomena of too dry inside and too damp in the attic usually do not appear in the same dwelling, but they can, and they have, because although these two conditions are moisture related, the causes can be unrelated.

A home may be relatively dry inside, that is, in the living area, but the moisture that has migrated into the attic might have become “trapped” in the attic due to poor attic ventilation.  Yes, even the small amounts of airborne moisture that migrate from the relatively dry living area.  The result is an accumulation of excessive airborne moisture in the attic and condensation on the cold framing members, such as, the underside of the roof deck and protruding nail ends, the tops of the rafters or trusses, the gable end walls, and metal components.

 

Tea colored staining on ceiling.

 

See our article There is Mold in My Attic for more information regarding this phenomenon.Prolonged condensation of airborne moisture can produce significant amounts of water that drip onto and through the ceiling insulation, onto and through the joints of the drywall, and appear as a tea-colored stain on the ceiling and/or walls.  Once on the interior the moisture evaporates, migrates through the ceiling and into the attic and the cycle repeats.  This is similar to the hydrologic cycle we observe in nature – evaporation, vapor rises, vapor condenses into clouds, clouds precipitate rain, rain drains into the rivers and lakes, and the cycle repeats.

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