Ice Dam

Ice dam formations are all too prevalent in many Northern climates in the United States. As soon as your roof has snow and ice accumulation for an extended period of time, your home could be susceptible to ice dams. Many factors can contribute to this issue, but attic ventilation is generally the best place to start in addressing this concern.

1. Snow accumulates on the roof.
2. The roof warms up from heat transferred from living to attic space and from the heat generated directly from the sun.
3. This warming is just enough to partially melt snow turning it to water. The water then runs down the roof line underneath the snow until it gets to the roof edge.
4. At the roof edge, the surface temperature is lower again causing the water to refreeze into ice. 
5. Over time, the snow can continue to melt higher on the roof, drip down as water and refreeze as ice on the roof edge.
6. As more water runs down, it can build up the ice and act like a dam keeping the water from running off properly.
7. This water can back up under your roof shingles and leak into your attic and into your home.

There are some visible signs to watch for to help you catch ice dams. According to This Old House, icicles hanging from your gutters are a definite red flag. As pretty as those icicles may be, they can actually be a sign that you may have a problem. Secondly, look for sections of melted snow on the roof that may indicate that water could be running down the roof. Lastly, check your attic and interior ceilings for signs of water, ice or other damage.

The ATMOX controller addresses heat and moisture within your attic. Additionally, the controller has an optional setup for mitigation of ice dams. This optional mode called “Snow Mode” allows your fans to bring in outside air into your attic when the air temperature outside is below freezing. Ideally, the attic temperature should remain as close to the outside temperature as possible. This may seem counterintuitive. However, under snowy conditions, you want your attic to be cold and drafty. This will then assist in reducing the melting and freezing cycle that leads to ice dams. 

To reduce the risk of ice dams, proper ventilation is essential. However, the heat transfer to the attic and ventilation must also be addressed. For example, sealing open cavities and properly insulating between the two spaces will create a necessary barrier. Creating this barrier between the living space and attic is vital to reduce warm air from seeping into the attic.