Each year, ice dams cause millions of dollars in damage to homes. Read on to learn how you can avoid this problem and save energy.

Find Out More

• How ice dams are formed
• How to prevent ice dams
• Temporary or emergency measures  

 Download our Ice Dams on Roofs fact sheet.

 How ice dams are formed

Ice dams form when heat enters an attic and melts snow on the roof. This melted snow runs down the roof, under the blanket of snow, to the edge of the roof where colder conditions cause it to freeze again, forming ice dams.

If ice dams are not removed, water may be caught behind them, and be forced under shingles or spill over to form icicles. This can result in costly damage to your home including:

• Wet (ineffective) insulation
• Stained or cracked plaster or sheetrock
• Damp, rotting walls
• Stained, blistered or peeling paint

How to prevent ice dams

Since the basic cause of an ice dam is a warm roof, the solution is to maintain a cold roof. You can do this by taking three steps:

1. Seal bypasses
2. Insulate your attic
3. Ventilate your attic

Seal bypasses

Any hole, crack or crevice that allows heated air to leak through and past insulation is known as a bypass. If bypasses are not sealed before insulating, the insulation only "filters" the warm air on its way to the attic, and your roof will still be warm. Bypasses are found:

• Around light switches, outlets and light fixtures (not recessed light fixtures)
• Around chimneys and plumbing stack pipes
• At the rim joist and foundation
• Around bathroom and kitchen ceiling vents and any other warm exhaust equipment
• Through dropped soffit (ceilings)
   

Insulate your attic

The basic function of insulation is to resist the flow of heat from your living space to the attic. It is rated by R-value; the higher the R-value, the better it resists heat flow.

• Different insulation materials have different R-values per inch. Buy insulation according to the R-value you wish to attain, not by inches.
• An attic floor should have an R-value of 38 to 44.
• Proper installation is as important as R-value. In many homes pipes, wires, recessed ceiling fixtures, bridging, and other things, break the continuity of insulation. These breaks, voids and thin spots allow heat to continue to enter the attic. An attic floor with sealed bypasses and properly installed insulation will be the most effective.

Ventilate your attic

Despite your efforts to seal bypasses, some warm, moist air from the living space may escape into the attic. Vents in the attic will help maintain a cold roof by allowing this warm moist air to escape. They also help prevent water vapor from condensing and collecting on insulation and rafters.

Temporary or emergency measures

If you already have water or ice dam problems, you need to take remedial action. The following methods are sometimes successful but will probably have to be repeated with every winter storm. Remember, these are only temporary or emergency measures.

• Remove snow with a "roof rake". Beware of icy conditions and falling snow and ice.
• Hose off ice dams with tap water on a warm day. Note that water runoff could damage shrubbery.
• Steam the roof. Note that steam could cause expansion and contraction of the roof deck.
• Install electric cables along the eaves and in the valleys of the roof to drain ice dams. Melting is limited to a few inches near the cables, and the saw tooth melting often causes secondary ice dams to develop higher on the roof. These cables also use a great deal of energy.
• Do not chop ice off the shingles or use a blowtorch. This could damage the roof.

A Home Energy Audit  from CenterPoint Energy can also help you identify ways to reduce or avoid ice dams as well as provide ways you can make your home more energy efficient.