With winters like many of us have been experiencing these past few
years, it is not uncommon for the weather to take its toll on our homes.
One of the more common problems that can occur after a snow fall is
the development of ice dams. Ice dams are build-ups of ice and the
formation of icicles on the base, eaves and other areas of a roof.

 roof shingles or behind fascia boards where it can soak through the roof decking or wall sheathing, causing damage to ceilings and walls.

Insulation
An attic insulated to today’s energy standards with fiber glass insulation minimizes heat escape through the ceiling, eliminating the possibility of snow melting and freezing at the base of the roof. 
If your home was built before 1980, chances are it needs more attic insulation. The amount of insulation your house should hay will vary depending on where you live, how your house is built and
many other factors including you lifestyle. Insulation levels are recommended by geo-graphic zones and are stated in R-values.

R-value is the resistance to heat flow of a
material. The higher the R-value the greater the insulating power.

The following map and chart indicate recommended levels of insulation
by geographic area.

R-values on the chart represent CertainTeed recommendations for meeting today’s energy standards. Department of Energy thermal
recommendations and the Council of American Building Officials Model Energy Code provided
the basis for CertainTeed’s insulation
recommendations.

Ventilation
The second thing to look for in your attic if you have a potential ice dam problem is the amount of ventilation that you have, It is important to have ventilation in the attic so any heat lost from the

interior of the home is drawn up and out of the  home is drawn up and out of the attic. Adequate attic ventilation will help the roof deck stay cool. Another benefit of having your
attic ventilated is that it allows for moisture that rises into the attic from things such as
bathing, cooking and the
laundry to escape. Unchecked moisture can promote mold, mildew and wood rot.

There are two common ways to ensure that excess moisture or heat can escape to the outside. One way is through a natural or static ventilation system. The other way is by a power or mechanical ventilation system. A power ventilator is an electric powered fan installed at the roof or
gable that runs by a thermostat or humidistat when the attic needs ventilation. Natural or static ventilation systems consist of simple vent or covered openings in your attic. These are typically ridge vents, gable, eave or roof vents. Many ventilation experts agree that externally baffled ridge vents combined with vented soffits are the most effective method for ventilating an attic.

A properly designed ventilation system must have both intake vents in the soffit or eaves at the lower part of the attic, and exhaust ventilation such as ridge vents high in the attic at or near the ridge.

Typically cooler, dryer outside air enters through eave vents near the attic floor, forcing existing moisture-laden or heated air out through
vents placed high on the roof or gable.

By ensuring proper insulation and ventilation, you will run less risk of the formation of ice dams and you will substantially reduce the likelihood of damaging your attic components.

Preventing Ice Dams
In New Homes
If you are building a new home, in addition to the points on insulation and ventilation mentioned above, which are important to discuss with your builder, you should also insist that waterproofing shingle underlayment be installed before your roof shingles are applied. As mentioned earlier, it is completely resistant to water and, as such, is a last line of defense against leaks, preventing backed up water from getting into your new home wherever it is applied.

One of the first products of its kind on the market was Certainteed WinterGuard, which is warranted to prevent water penetration for the warranted life of the new asphalt shingles applied over it (up to a maximum of 30 years). While shingle underlayment does not prevent the formation of ice dams, it will prevent backed up water from getting into the house. Discuss shingle underlayment placement with your builder. However, as a guide, the CertainTeed Home Institute recommends that it be applied:

• Under metal flashing and counter flashing at every roof penetration.

• In areas where roof pitches change, in valleys, at joints at building additions, and at water stops behind chimneys.

• At eaves of homes and at short cornice projections.

Preventing And Resolving
Ice Dam Concerns
While the causes of ice dams are many and complex and the likelihood that they will form unpredictable and weather-dependent, steps can be taken, as this pamphlet has shown, to prevent them in new homes and help reduce their impact in existing ones.

To ensure that ice dams and the damage that they cause do not result in costly leaks, make sure your home is properly insulated, the attic properly ventilated, and shingle underlayment applied to vulnerable areas of the roof when re-roofing, adding onto a home or constructing a new one.

Skylights
In the case of skylights, quality workmanship and attention to detail are important in preventing ice dams and condensation, which often lead to
leaks. To avoid problems, make sure your builder properly insulates around the skylight and uses a moisture retarder to prevent condensation. In addition, applying waterproofing shingle underlayment around the skylight opening is recommended. Also discuss with your builder the importance of the finish being properly fitted and sealed.