How Proper Attic Insulation Can Help Prevent Ice Damming
Feb 12, 2026
After the harsh winter of early 2025, many Ontario homeowners experienced firsthand the costly damage ice dams can cause. Now that we're experiencing winter 2026 in Ontario, understanding how proper insulation can prevent ice damming and protect your home is an important educational opportunity for homeowners.
What Is Ice Damming?
Ice dams form when snow on your roof melts due to heat loss from your home, then refreezes at the roof's edge where temperatures are colder. A major cause of ice damming is heat loss from your home due to inadequate insulation. However, it’s important to note that ice formation does not always equal ice damming.
Freezing and thawing cycles are part of a standard winter day throughout the entire season. Even on the coldest winter days, sunlight can still cause existing snow to melt on rooftops, with the water runoff flowing downward. As the angle of the sun shifts throughout the day, the flowing meltwater can refreeze and accumulate into icicles, even without building heat loss being a factor. Other secondary factors can include roof pitch, direction, and even roofing material colour. Darker, south-facing roofs, for instance, are more prone to absorbing heat during sunny winter days due to the amount of sunlight they get.
Understanding the heating and cooling cycles, weather behaviour, and building insulation is what allows Great Northern Insulation to determine whether ice formation is normal behaviour of a home through an Ontario winter, or if action is required to reduce ice damming and potentially prevent damage to the home.
For a historical example: the cyclical weather pattern Ontario experienced in February and March 2025 of significant snowfall followed by warm days and freezing nights created perfect conditions for ice formation, including ice damming. Great Northern Insulation saw hundreds of requests for assistance with ice dams, which can be difficult to address deep into the winter season.
|
Does Insulation Stop Icicles? Not always, and that's okay! While proper attic insulation is one of the most effective ways to prevent ice dams, icicles themselves don't automatically mean you have a damming problem or that your insulation is inadequate. Icicles can form even with perfect insulation when snow melts from direct sunlight warming your roof surface, outdoor temperatures fluctuate above and below freezing, or when your roof has minimal overhang where melting snow naturally drips and refreezes. |
How Proper Insulation Prevents Ice Dams
So, it’s been determined that inadequate attic insulation is a factor in your home’s ice damming issues. How exactly does proper insulation help prevent ice damming?
Temperature Control: Adequate attic insulation, combined with effective air sealing, helps maintain consistent roof temperature by preventing heated air from your living spaces leaking into and warming your attic.
Reduced Heat Loss: Proper insulation minimizes the heat that escapes and causes snow to melt prematurely, reducing the freeze-thaw cycle that can contribute to ice damming.
Cold Roof System: When combined with proper attic ventilation, good insulation helps create a "cold roof" system where the roof surface stays close to outdoor temperature.
Current Ontario Building Code generally requires R-60 insulation in attics. Homes with inadequate insulation, such as missing insulation or old fiberglass batts, are at higher risk for ice damming.
Other Contributing Factors
While insulation is crucial, ice dams can also result from:
- Inadequate attic ventilation
- Blocked soffit vents
- Heat from recessed lighting or heating ducts in the attic
- Poor air sealing between living spaces and the attic
- Clogged or frozen eavestroughs preventing proper drainage
Long-Term Prevention Strategies
Insulation Upgrades: Bring your attic insulation up to minimum R-50 code requirements by having Great Northern Insulation install blown-in cellulose, spray foam insulation, or a combination of the two. Be sure to ask about available rebates!
Air Sealing: Seal gaps in the attic floor that allow warm air to escape from the conditioned living area into the attic space
Proper Ventilation: Ensure adequate intake and exhaust vents for proper airflow. An attic space needs to be properly insulated, but it also needs adequate ventilation in order to operate effectively
Duct Insulation: Insulate any heating ducts located in attic spaces – these can be major sources of heat loss into the attic space
Immediate Winter Preparation
While planning insulation upgrades:
- Clean gutters and ensure proper drainage before winter
- Check that soffit vents aren't blocked by insulation or debris
- Address any obvious air leaks around the attic hatch
- Remove snow from lower roof areas after heavy snowfall
Professional Assessment
Preventing ice dams requires a comprehensive approach that considers insulation, air sealing, and ventilation as an integrated system. However, ice damming is a complicated issue that can persist even with all factors considered. Complications like inaccessible attic areas (including dormers, framing behind areas that have been drywalled, etc.) or even fluctuations in weather conditions or wind direction can make mass ice damming difficult to diagnose or fix. For those reasons, it’s best to get an opinion from the professionals, and schedule a free attic consultation from Great Northern Insulation before winter weather approaches.
Don't wait for ice dams to form this winter. Contact Great Northern Insulation for a free assessment of your attic insulation and ventilation system. Our experienced team will help you understand how proper insulation protects your Ontario home from ice damming and keeps your family comfortable all winter long.
