Most ice dams are caused by a rather vicious, man-made cycle. Here is the life cycle of the average ice dam.
- Snow falls on the roof.
- The roof is hot enough to bring the temperature of the snow above freezing.
- The snow melts.
- Run off from the melted snow reaches colder overhangs and gutters. The temperature of the water drops below freezing once more.
- The water freezes, slowly forming a wall of ice.
- Additional snow continues to melt, pooling behind the wall of ice until it finds its way underneath your shingles and begins leaking into your home.
Obviously an ice dam can form any time the snow on your roof begins to melt and re-freeze. Mother Nature can often do this on her own. However, most of the time Mother Nature isn’t the culprit at all. Your hot roof is the culprit!
Hot Attic, Hot Roof!
Your roof can only get hot if your attic is getting hot too.
When you run your heater that heat is supposed to stay in the living areas of your home. After all, you’re not watching football in your attic. You’re doing that in your living room. Any heat that sneaks into your attic is wasted, harmful heat. You don’t want it there.
But in many homes, heat is sneaking up to the attic anyway. There are a couple of ways to combat this.
Insulation
The first thing you’re going to want to address is insulation. Many homes do not have enough insulation at a sufficient R-value to prevent heat from seeping into their attics.
Some homes simply don’t have insulation in the right places. For example, if your HVAC ducts run through your attic then they are going to need a great deal of insulation around them if you don’t want them to create a hot attic!
Ventilation
Roof ventilation is designed to help heat escape. Some homes don’t have enough ventilation to allow enough cold air in and/or enough hot air out. Sometimes the vents are closed when they need to be wide open. Sometimes snow completely clogs them (which by the way is another great argument for clearing the snow from your roof to prevent ice dams).
You also need to watch the way the ventilation is set up on certain interior systems, namely: your stove vents and bathroom exhaust fans. Often, these systems vent directly into the attic (this is bad). These pipes should be running directly outside of the home, where they should be capped with a vent hood, caulked, and fitted with flashing to avoid leaks.
Attic Bypasses
There are a lot of little spaces in your home that allow heat to slip into the attic. These are commonly referred to as “attic bypasses.”
You’ll find them in small, subtle gaps between the wall and your outlet plugs. You’ll also find bypasses around plumbing vents and electrical wires. You might also find them around furnace flues. In fact, any place you have a penetration through a wall or ceiling is a potential air leak into your attic.
The best way to take care of attic bypasses is to get a home energy audit done during the summer months. A home energy professional can help you find nearly every bypass. They’ll also get them sealed up for you.
As a bonus, they’ll help you cut your home energy bills too. There aren’t too many people who enjoy paying extra money to heat up their attic during the winter time, especially when it causes an ice dam!
Once Attic Heat is Under Control, You Should See Fewer Ice Dams.
Ideally, your attic temperature will be very close to the air temperature outside. Once this happens your roof should stop melting the snow for the most part. After that, you should only have to worry about ice dams that are caused by temperature fluctuations during the warmer winter months, either when temperatures slip above freezing during the day but drop below freezing at night or when radiant heat from the sun causes snow to melt during the day. At the very least, you will no longer be contributing to the problem by providing ice dams with the toasty warm roofing they love so very much.