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How to Identify Attic Condensation and What to do About it

You never want to ignore the problem of attic condensation because it can completely destroy your roof.  This is especially true here in the Pacific Northwest, with tons of steady rain and moderate temperatures.

Mold can grow rapidly in this climate, and this can lead to moisture seeping into the wood of your roof and rotting it from the inside out.

We’ve replaced many roofs on homes where condensation deteriorated the wood sheathing so much that most of it needed to be replaced with new plywood.  In this article, we’ll explain what you can do to prevent your roof from suffering such damage.

Check your attic for signs of condensation

Here you’re looking for any visible signs of water in the attic: stains, rust, dampness, droplets on the bottom side of nails, or moisture signs of any kind.

Even without visible moisture, a musky odor can reveal condensation issues.

Check for air gaps between the house and the attic

If the seal between the conditioned space of the house and the unconditioned space of the attic isn’t tight enough, both air and moisture will leak through.

Check vent connections

Any pipes originating from inside the house, like bathroom vents, need to be routed properly to the outside of the roof.  If they’re not, then a bunch of heat and moisture will pour into your attic from inside your house.

Check for intake and exhaust ventilation

Your roof should have only two types of ventilation: one along the eave perimeter of the attic, and one along the ridges.

Eave ventilation is typically in the form of bird blocks or continuous intake vent that is cut into the topside of the roof at the edge of the attic.  Exhaust ventilation is typically either continuous ridge vent all along the peak of the roof, or static mushroom-type vents just below the peak.

Venting often gets mixed up and this causes a problem, because it disrupts the air flow.  When air doesn’t circulate fully from the lowest part of the attic to the highest, you’ll get dead spots that can generation condensation.

The attic should be about the same temperature as the outside.  If it’s not, it means ventilation isn’t pulling enough outside air through the intake vents and pushing it back out through the exhaust vents.

Check insulation level and position

It happens way more often than one might think that attic insulation is installed improperly or is moved around after the fact.  This can lead to huge problems, particularly by blocking airflow from intake vents to exhaust vents.

The typical mistake is when insulation is pushed up against the intake vents down by the bottom edge of the sloped sides of the attic.  If insulation is stuffed too much into the intake paths, condensation will almost certainly arise in the attic.

We service the South Puget Sound of Washington State, and if you potentially have any of these issues, please call us at (253) 544-3651 or fill out our quick estimate form.

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