Ice Dams
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Those Darn Ice Dams! Ice dams don’t occur every year, but when they do, they almost always cause hundreds or thousands of dollars in damage due to leaks into the house which can ruin ceilings, walls, lighting fixtures, personal belongings and insulation, cause the growth of mold and mildew, promote Sick House Syndrome, destroy gutters and awnings, and in some cases encourage roof collapse. Here’s how to prevent ice dams:
PROFESSIONAL Ice Dam Removal is a delicate job that must be done correctly. We remove ice dams with special techniques and tools such as Rubber Mallets and plastic snow rakes. Approximately 3 to 4 feet of ice and snow will be removed from the roofing system edges. (Please note: Non-professional methods such as hatchets, ice picks, Metal Hammers and/or ice-melting compounds are not advisable). They present potential hazards to your roof and gutter system.) Ice dam formation can cause serious damage to your roof and shingles, which in turn causes leaking and interior water damage. This can result in thousands of dollars of damage to your family’s home. There is also the potential for black mold growth if it is not caught and taken care of right away. Prevent ice dam leaks and keep the roof in good shape. These are starting prices for homes that are 2000 sq. feet or less. Pricing depends on the snow fall and ice, as well as the home design. All custom, larger homes of more than 2000 square feet and/or more than 150 lineal feet of the existing roofs gutter edge. (Homes with over 150 lineal roofs gutter edge will be an extra charge of $10.00 per over the 150 feet). Homes more than three stories high, need to be estimated. Please call for pricing — it only takes a minute with our software. |
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PRICING SPECIAL – Approximately 3 to 4 feet of ice and snow will be removed from the roofing system edges.
These are starting prices for homes that are 2000 sq. feet or less. Pricing depends on the snow fall and ice, as well as the home design. All custom, larger homes of more than 2000 square feet, homes more than three stories high, and if the steamer is used, need to be estimated. Please call for pricing — it only takes a minute with our software. Please note: Sales tax is added to all service jobs. Our professionals are insured with Worker’s Compensation Insurance, and we carry $2,000,000.00 in liability insurance.
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We subscribe to satellite service. We give them your address, color and what type of house and they send us the satellite picture of your home. An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow (water) from draining off the roof. The water that backs up behind the dam can leak into a home and cause damage to walls, ceilings, insulation, and other areas. Figure 1 shows a cross section of a home with an ice dam.
What causes ice dams?
Figure 1. Cross section of a one-and-a-half story house with an ice dam.There is a complex interaction among the amount of heat loss from a house, snow cover, and outside temperatures that leads to ice dam formation. For ice dams to form there must be snow on the roof, and, at the same time, higher portions of the roof’s outside surface must be above 32°F while lower surfaces are below 32°F. For a portion of the roof to be below 32°F, outside temperatures must also be below 32°F. When we say temperatures above or below 32°F, we are talking about average temperature over sustained periods of time.
The snow on a roof surface that is above 32°F will melt. As water flows down the roof it reaches the portion of the roof that is below 32°F and freezes. Voila!—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°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. From the attic it could flow into exterior walls or through the ceiling insulation and stain the ceiling finish.
Nonuniform roof surface temperatures lead to ice dams.
What causes different roof surface temperatures?
Since most ice dams form at the 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 the heating of 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 through the slanted portion of the ceiling (Figure 1). In many homes, there is little space in regions like this for insulation, so it is important to use insulations with high R-value per inch to reduce heat loss by conduction.
The top surface of the insulation is warmer than the other surroundings in the attic. Therefore, the air just above the insulation is heated and rises, carrying heat by convection to the roof. The higher temperatures in the insulation’s top surface compared to the roof sheathing transfers heat outward 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. In Figure 1, the winding arrow beginning inside the house and going through the penetration in the ceiling, from the light to the attic space, illustrates heat loss by air leakage. In many homes this is the major mode of heat transfer that leads to the formation of 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 of high snow fall.
Other sources of heat in the attic space include chimneys. Frequent use of wood stoves and fireplaces allow heat to be transferred from the chimney into the attic space. Inadequately insulated or leaky duct work in the attic space will also be a source of heat. The same can be said about kneewall spaces.
The photograph below left shows a single story house with an ice dam. The points of heat loss can be clearly seen as those areas with no snow. The ceiling below this area needs to be examined for air leakage, missing or inadequate insulation, leaky or poorly insulated ductwork, and the termination of a kitchen
The photograph below right illustrates unusually high heat loss from the roof. There is very little snow left on the roof and at its edge is both an ice dam and a “beautiful” row of icicles.
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| A single-story house with an ice dam. The areas without snow are the points of heat loss. | The unusually high heat loss on this roof has caused both an ice dam and icicles. |
Natural roof ventilation can help maintain uniform roof temperatures, but if the long-term actions described here are done effectively, then only small amounts of roof ventilation are needed to maintain uniform roof surface temperatures. If heat transfer has been reduced substantially, then snow will build up on the roof and cover natural roof ventilation systems, reducing attic ventilation rates. Natural attic ventilation systems are needed to dry the attic space and remove heat buildup during the summer.
