What are Ice Dams and Why You Should Get Rid of 'Em?

Ice dams are the result of melted snow and ice running off a roof and freezing when losing contact with heat, usually atop the roof’s overhang. As heat escapes from the roof of a house, it melts the snow at the roof level. The melted snow travels down the roof as it runs off, but freezes again as it comes into contact with a part of the roof where no heat escapes. A roof’s overhang is insulated against heat escaping from the home and the temperature of the roof material atop the overhang is the same as the temperature outdoors. It is here where the melted snow freezes and creates an ice dam.
As the dam thickens, more water is retained as a reservoir of melted snow runoff is trapped on the roof by the ice dam. It is this reservoir that causes the damage to homes. Shingles are designed to displace water as it flows by, but not designed to endure standing water. The standing water then makes its way past the shingles and through the roof materials behind the walls. Icicles form at the edge of the ice dam as some of the water from the reservoir spills over the dam and makes its way toward the ground.

What causes Ice Dams?
Nonuniform roof surface temperatures lead to ice dams. Heat loss from a house, snow-covered roofs and outside temperature interact and lead to ice dam formation. For ice dams to form, there must be snow on the roof, and, at the same time, the upper portions of the roof’s surface must be above 32 degrees F, while lower surfaces are below 32 degrees F. For a portion of the roof to be below 32 degrees F, outside temperatures must also be below 32 degrees F. (When we say temperatures above or below 32 degrees F, we are talking about average temperatures over sustained periods of time.)

The snow on a roof surface that is above 32 degrees F will melt. As water flows down the roof, it reaches the portion of the roof that is below 32 degrees F and freezes. This creates an ice dam.

The dam grows as it is fed by the melting snow above it, but it will limit itself to the portions of the roof that are, on the average, below 32 degrees F. So the water above backs up behind the ice dam and remains a liquid. This water finds cracks and openings in the exterior roof covering and flows into the attic space. In the most common case, the water simply backs up and flows under the shingles. From the attic, it could move into exterior walls or through the ceiling insulation and stain the ceiling finish.

What causes Different Roof Surface Temperatures?
Since most ice dams form at the lower edge of the roof, there is obviously a heat source warming the roof elsewhere. This heat is primarily coming from the house. In rare instances, solar heat gain may cause these temperature differences.

Heat from the house travels to the roof surface in three ways: conduction, convection and radiation. Conduction is heat energy traveling through a solid. A good example of this is heating a cast iron frying pan. The heat moves from the bottom of the pan to the handle by conduction.

If you put your hand above the frying pan, heat will reach it by the other two methods. The air right above the frying pan is heated and rises. The rising air carries heat/energy to your hand. This is heat transfer by convection. In addition, heat is transferred from the hot pan to your hand by electromagnetic waves, and this is called radiation. Another example of radiation is to stand outside on a bright, sunny day and feel the heat from the sun. This heat is transferred from the sun to you by radiation.

In a house, heat moves through the ceiling and insulation by conduction. In many homes, there is little space in regions like this for insulation, so it is important to use insulation with a high R-value per inch to reduce heat loss by conduction.

The top surface of the insulation is warmer than the other areas in the attic. Therefore, the air just above the insulation is heated and rises, carrying heat by convection to the roof. The higher temperature in the insulation’s top surface, compared to the roof sheathing, also transfers heat to the roof by radiation. These two modes of heat transfer can be reduced by adding insulation. This will make the top surface temperature of the insulation closer to surrounding attic temperatures, directly affecting convection and radiation from this surface.

There is another type of convection that transfers heat to the attic space and warms the roof: warm air leaking from the living space. In many homes, this is how heat transfer happens. This can cause ice dams. Exhaust systems like those in the kitchen or bathroom that terminate just above the roof may also contribute to snow melting. These exhaust systems may have to be moved or extended in areas where lots of snow may accumulate.

Other sources of heat in the attic space include kneewalls, leaky ductwork and chimneys. Frequent use of wood stoves and fireplaces allow heat to be transferred from the chimney into the attic space and then to the roof. 

LEAVE IT TO THE PROS! DON'T TRY TO DO IT YOURSELF

Ice dam removal is highly recommended to be done by professional contractors: NEVER attempt to go up on an icy or snowy roof. DO NOT attempt to remove ice dams unless you have experience doing so and know exactly what to do. You could seriously injure yourself if you are not skilled at removing ice dams. You can also damage your roof and possibly have some structure damage if you are inexperienced in this type of work.

The professionals at Vertex Roofing are the ones to call when you need Ice Dams removed. We use a steam machine to remove your ice dam; it is the most safe and efficent way to perform this service and not cause serious damage to your roof. Call us today 877-METAL37 and talk to one our talented professionals about your Ice Dam issues today!

Vertex Roofing TV Commercial

This is our ad currently featured on FOX News21. For more information on our products or how you can set up an appointment to speak with a member friendly & knowledgeable sales team, visit Vertex Roofing

Vertex Roofing YellowBook Commercial

Here is our YellowBook Commercial Ad that is on YouTube. You can find out more information on our Vertex Metal Roofing Systems at: our website! Thanks for stopping by.