A Tale of Ice and Foam: The Fight Against the Winter’s Ice Dams
Once upon a chilly winter, in a small town where rooftops were blanketed with snow, the inhabitants faced a foe as relentless as the frosty season itself – the ice dams. These icy invaders, fashioned by nature’s wily forces, formed a ridge at the edge of the roofs, hindering the escape of melting snow. Their presence was more than just a winter spectacle – they bore the potential for ruin, causing leaks that could infiltrate homes, damage walls, ceilings, and insulation, and even foster mold and mildew.
The people of the town often wondered why some roofs lay heavy with snow, while others were practically bare. A curious contradiction, as it was the snowy roofs that signified well-insulated homes, while the bare ones were at the mercy of ice dams. The key, they realized, was controlling the heat loss from their homes.
The Birth of the Ice Dam
The formation of ice dams was an intriguing dance between heat loss, snow cover, and outside temperatures. The town’s attics would turn into warm sanctuaries as heat escaped from the living spaces below and radiated from hidden recessed lights, ductwork, and various appliances. This warmth would conduct through the roof sheathing, causing the snow and ice on the roof surface to melt.
To form the ice dams, there had to be snow on the roofs, and at the same time, the higher portions of the roof’s outside surface had to be above 32°F, while the lower surfaces were below 32°F. The snow atop the warmer part of the roof would melt and flow down, only to freeze once it reached the colder parts, giving birth to an ice dam. As more snow melted from above, the dam grew, holding the water above it hostage. This trapped water found its way through cracks and openings in the exterior roof covering, flowing into the attic space, and from there, into exterior walls or through the ceiling insulation, staining the ceiling finish.
The people noticed that the snow and ice tended to melt in the areas just inside the exterior walls. The resulting liquid would flow downward, refreezing as it passed over the roof overhangs, just above the soffit vents. This ice would accumulate at the roof edge and in the gutters, forming a dam. With each snowfall on the warm roof surface, more liquid water would form, flow over the ice buildup, and create icicles along the roof’s edge.
The Icy Consequence
Ice dams were more than just a sign of poor insulation – they were a brewing storm of potential issues. Melted snow and ice could seep under the shingles and saturate the roof deck. Water could drip onto the ceiling insulation or leak into the areas where the roof connects with the exterior walls. Damp walls and ceilings were prime territories for mold and mildew growth, posing respiratory threats to the inhabitants. Ice dams could also pose a physical danger, as the liquid water could decrease the friction between the snow and the roof surface, leading to mini-avalanches. If the ice dam broke free, it could rip off shingles and gutters, damaging anything it fell on, including windowsills, cars, and even passersby from falling icicles.
Spray Foam Insulation to the Rescue
The solution to the ice dam menace lay in sufficiently insulating and sealing the attic spaces, and the most effective method was the unvented attic. These were enclosed, conditioned spaces within the home’s building envelope, just like the living spaces. Insulation was applied to the underside of the roof decking rather than the attic floor and along the rim joist. The only insulation material that could be used is spray foam insulation, as batt insulation will sag and blown insulation will fall. Spray foam insulation can help stop meltwater from entering and damaging your home. You can avoid leaks and save money on ice dam repair costs by installing a layer of spray foam insulation between your roof and attic.
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