Ways to Conquer Ice Dams Before They Start
Dec 16, 2015Ice dams sneak into a home silently, on a winter day, as a build-up of snow sits on a house’s roof. In this stealthy scenario, while the temperature outdoors drops to below freezing, the temperature inside the attic is above freezing. The villain here is heated air rising from the home’s living space, escaping upward where it shouldn’t. The heated attic air warms the roof.
The heated roof causes the blanket of snow on top of it to start melting from the bottom up, and rivulets start trickling downward. The melted snow water tries to flow down and off the roof. However, when the water emerges at the edge of the roof, it’s exposed to the freezing air, and the water refreezes.
Where the water was once snow at the peak of the roof, it’s now ice along the eaves and gutter area. As this melting and freezing cycle is repeated, the water has nowhere to go. It is trapped behind — and on top of — the previously frozen deposits, and the ice dam grows.
Trapped water doesn’t freeze immediately. In the meantime, house materials that come in contact with it are soaked, resulting in interior water damage. Unless corrective steps are taken, the water problem can recur, along with continued heat loss along the pathways that allowed the heated air to escape in the first place.
You can’t totally eliminate freeze and thaw cycles. The goal is to manage the situation so it doesn’t cause damage. You’ll still get some icicles, but try to work with Mother Nature rather than fight her. The big things are to properly install an ice and water shield, have proper ventilation in your attic, and have good insulation. Get your insulation evaluated, and look for areas where heat is escaping from the living space into the attic. It’s a critical item if your attic is getting too hot.”
Diagnostic Tests
You may also want to take advantage of diagnostic tests performed by home energy auditors and home performance contractors, such as a “blower door test,” which uses a huge fan hooked up to a house door. The air flow can pressurize or depressurize the air in the home. A pressure gauge reader helps determine how leaky the house is by recording the pressure reading in the home.
Also, infrared cameras are used to show the air paths, cold points in the attic, voids in the insulation, and other bypasses in their houses.
Milwaukee/NARI also recommends homeowners hire a professional to conduct an energy audit.
The solution is not to simply add more and more insulation to a house, but to pinpoint with diagnostic tests where the bypasses are, and strategically solve the problem.
For example, one house alone could have 40 leaky areas. Insulation options for various uses can range from fire-retardant foam board to fiberglass insulation to dense-pack cellulose to spray insulation to fill cracks, among others. A qualified contractor is also a good source of practical information on homeowner incentives, such as rebates and tax credits.
Myths About Ice Dams
While winter weather is beyond control, sorting out fact and fiction can help homeowners navigate a problem. Below are some myths and realities about ice dams.
Myth 1: Sun shining on a roof raises the exterior roof temperature enough to start runoff that leads to an ice dam.
Reality: With rare exceptions, sun exposure in the winter has little effect on attic air temperature. Warm interior air from living spaces below is usually to blame.
Myth 2: Only old houses are plagued with ice dams.
Reality: New construction can fall victim, too.
Myth 3: The west side of the house, warmed by afternoon sun, is afflicted the most.
Reality: All sides of the house are vulnerable.
Myth 4: It’s effective to chip away at ice dams and remove snow from the shingles.
Reality: Be wary of chipping. Since roofing materials are more brittle in the winter, shingle damage can result. To drain the ponding water, hire a contractor to create one or two grooves in the ice dam for runoff. A contractor can carefully remove most of the snow from the roof above the ice dam.