While
stopping a leak or repairing a washing machine hose down in the basement might
be fairly straightforward, ice dams and attic condensation, two forms of water
damage typical to our cold Maine winters, are a little more complicated and a
little trickier to fix. And since many homeowners aren't frequent visitors to
their own attics in the frigid winter months, water damage on the top floor
might catch you off guard.
What
are ice dams? What causes attic condensation? And if you've got either, what
can you do?
Ice
dams
When
the temperature in your attic is above freezing, snow on the roof will likely
melt. When the snowmelt runs down the roof and hits the colder eaves, it
refreezes.
If
this cycle repeats over several days, the freezing snowmelt builds up and forms
a dam of ice, behind which water pools up into large puddles, or 'ponds'. The
ponding water can then back up under the roof covering and leak into the attic
or along exterior walls.
The
right weather conditions for ice dams are usually when outside air temperatures
are in the low 20s (°F) for several days with several inches of snow on the
roof.
Attic
condensation
Condensation
of water vapor on cold surfaces in attics can cause wood to rot, which can lead
to costly repairs.
Condensation
typically occurs when warm, moist air migrates or is directed into the attic
from living spaces below. Research indicates unusually high humidity in the
home's living spaces is strongly associated with attic condensation problems.
Prevention
Building
codes have some requirements that attempt to prevent the problems of ice dams
and attic condensation. But codes don't address all the issues, and many houses
are built without following building codes. First and foremost, it's your
builder or designer's job to understand the relationship of humidity and air
movement when designing and constructing the house so these problems don't
occur.
Nevertheless,
there's more you can do. Here are a few simple steps that can help prevent ice
dams and condensation in your attic:
Bathroom
and kitchen exhaust fans, as well as dryer vents, should never be discharged
into the attic space, always discharge outside. You may have an adequately
ventilated attic, but this won't matter if the bathroom exhaust fan dumps warm
moist air directly into the attic space. This will result in condensed water
vapor freezing onto cold attic materials, which will eventually thaw creating
wet attic materials resulting in damage in the attic and inside the home.
Minimize
ceiling mounted fixtures below the attic that create the need for holes in the
drywall or plaster ceiling. Properly seal ceiling penetrations to make them
airtight, taking care to follow manufacturer clearance requirements for flues, chimneys,
and recessed light fixtures.
Research
shows keeping the attic air temperature below freezing when the outside air
temperature is in the low 20s can reduce the occurrence of ice dams. Proper
attic ventilation is key to keeping the attic cool, while adequate and properly
installed insulation is key to keeping your house warm. It is critical to keep
soffit vents free from obstructions to allow the natural flow of cool outside
air into the attic space to replace the warmer attic air that rises and flows
outside ridge and/or roof vents. This flow of air will keep the attic cool and
free of moisture build-up.
Consult
a professional for the best way to avoid ice dams and water damage in your
home.
What
not to do
While
it might be tempting to try a quick-fix to break up that ice dam, don't get too
eager; not only is it dangerous on your roof, but you can also cause a lot of
damage, especially in the colder months. Here are some things to keep in mind:
Do
not attempt to "chip away" the ice of an ice dam. It will likely lead
to shingle damage.
Do
not install large mechanical equipment or water heaters in attics, especially
in cold climates. Not only do they present an unwelcome fire hazard, but
they'll also increase the temperature in your attic.
Do
not routinely use salt or calcium chloride to melt snow on a roof. These
chemicals are very corrosive and can shorten the life of metal gutters,
downspouts, and flashings. Runoff that contains high concentrations of these
chemicals can damage nearby grass and plants.
What
to do
Follow
up with your new home or home-improvement contractor to be sure that insulation
in the attic space is adequate for your location.
Verify
soffit and roof or ridge venting exists for all roof planes and that soffit
vents are neither blocked by attic insulation nor covered by newly installed
maintenance free finishes outside the home.
Verify
all penetrations, access panels, and electrical fixtures are properly sealed
and insulated to prevent heat and moisture from entering the attic space, while
maintaining manufacturer's required clearances.
Verify
all exhaust fans and dryer vents are discharged to the outside.
Keep
gutters clean of leaves and other debris. This will not necessarily prevent ice
dams, but clean gutters can help drain ice melt away as it makes its way to the
gutters during a thaw.
Follow
up a short-term ice dam remedy with determining and fixing the actual cause to
your ice dam problem. Consult a trusted and competent professional.
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