Ice dams: the Dangers and Remedies
In simple terms, an ice dam is a ridge of ice that develops at the edge of a roof and prevents snow from adequately draining once it begins to melt. As moisture begins to build up behind the dam, it can put increased pressure on roof shingles, and start to leak through into a home, causing damage to ceilings, walls, insulation and other areas. Although ice dams do not cause the problem by themselves, without a properly installed ice and water shield membrane in your roof, you could find that your house suffers significant damage.
Often, these dams are formed when an interaction takes place between outside temperatures, snow cover, and heat that is lost through the roof. When snow accumulates on your roof, the warmer portions begin to melt the snow, allowing water to drain down to the colder portions below. This water usually gathers at the roof edge, known as the eave, and re-freezes into an ice formation which keeps liquid from draining into the gutter, as it should be.
The Dangers of Ice Dams
Ice dams present a significant problem to home owners, because they force water to leak from the roof into the envelope of the building (the ceiling and walls). This could lead to issues such as:
Rotted rafters, roof decking, and interior or exterior wall framing and sheathing.
Respiratory illnesses such as asthma, allergies, and so on for people in your household, generally caused by the growth of dangerous mold.
Icicles which grow to ridiculous sizes, which can then break off and cause massive roof, gutter and siding damage. In some cases, these icicles can severely injure the people who are unluckily standing beneath them when they choose to fall.
Reduced insulation effectiveness. Insulation that is wet does not work well, and chronically wet insulation will fail to decompress even after it has dried out. Without proper insulation, more heat can escape to the roof, melting more snow, and causing further ice dams, which in turn lead to leaks, and so on.
Peeling paint. Water from your roof leak can infiltrate the cavities of the wall and cause paint to blister and peel. This can happen sometime after the ice dam has dissipated, which means it is often written off as something else.
One of the best ways to prevent ice dams is to keep your entire roof cold, or at an equal temperature. This can be accomplished by a number of measures, including the installation of a metal roof, as the design will not allow any melting water to penetrate the surface.
Ensure that all air leaks are sealed within an attic floor, such as those surrounding hatches, wire and plumbing penetrations. This will help to guard against heat loss, and stop humidity from entering the attic.
Some older houses have insulation installed on the floor of the attic. However, modern techniques insulate the underside of the roof, extending the envelope of the building to include the attic area. Because of this, the space is sealed, rather than ventilated.
Try to remove snow from the roof when possible. Be careful that you do not harm any roofing materials or accidentally dislodge dangerous icicles in the process. Instead, create channels for the ice by hosing it with warm water. Remember, this should only be done in emergencies, as adding extra water to your roof is not typically a good idea.
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