I absolutely love snowfall in the winter. It’s a great payoff for all the shorter, colder days. What I don’t love is a homeowner calling because water is leaking into their home due to ice dams.
Ice dams cause millions of dollars a year in damage in the form of water-stained ceilings, rotted roof sheathing, deformed gutters, peeling paint, compromised insulation, mold infestation, and more. Cleaning up the mess left behind from an ice dam leak is a lousy way to spend what otherwise is a beautiful time of year. Even worse, these leaks can go on for days and ebb and flow with the freeze-thaw cycle due to daily temperature swings…or until there is no more snow on the roof.
My first experience with ice dams occurred many years ago when I got a call from a homeowner telling me that the windows we put in were leaking. She was upset, and I don’t blame her; water was dripping in from the tops of her newer windows in the second floor bedrooms. When I arrived, I noticed the carpets and the 2nd floor ceilings were wet as well. The leak was very active and she had towels everywhere. It was a real mess!
Recently, I visited a 40-year-old home in Blue Bell that was beautifully remodeled. Ice dams had formed for the first time and the homeowner was perplexed, stating that it never happened before. During the remodel, they introduced many recessed lights and speakers into the cathedral ceilings below the area of ice dams. These ceiling penetrations allowed indoor heat to reach the underside of the roof deck and accelerate snow melt, and the resulting ice dams.
Ice dams are caused by heat loss. They form when snow on your roof melts from an unusually warm attic. The melted snow runs down the roof, re-freezes at the cold roof edges, and dams of ice and icicles form. As more melted snow runs down the roof, it pools above the “dam” and leaks through the roof, and into the attic and exterior wall cavities.
Proof of this heat loss theory is easy to see. Take a look at a house with many large icicles along the eaves, then, look at the garage roof with the same exposure to the sun. You will find that the unheated garage has little or no icicles. I’ve noticed that an un-heated, unoccupied home on my street develops no icicles while every other home, regardless of solar orientation has them.
The solution for ice dams is multi-faceted. The first step is to stop heated air from escaping into the attic and is called air sealing. We do this by sealing recessed light fixtures, exhaust fans, attic accesses, and any other penetration through the second floor ceiling. We also need to seal up plumbing, electrical, HVAC chassis. These holes tend to connect the basement with the attic and usher conditioned air to the great outdoors.
Other offenders are the gaps between the chimney masonry and framing, and the gaps at the top of balloon framed walls. Some products involved with air sealing are fire rated spray foams and caulks, weather-stripped and insulated attic accesses and retrofit sealed recessed light trim kits.
The next step is a thermal boundary appropriate for your climate. This means insulation. Blown in cellulose is a great choice, especially when there is a chance of water infiltration. When it covers the joists, it has the added benefit of providing a thermal break for the framing members, minimizing heat conduction. The effect will be that you’ve contained the heat inside of your home.
After air sealing and insulating, be sure you have adequate passive roof ventilation. This may be achieved by introducing ample eave/soffit vents in conjunction with a continuous ridge vent. This allows for natural convective air movement across a large percentage of the roof deck. It will keep your attic cold in the winter, minimizing the pre-mature snowmelt that causes ice dams. In the summer, you will have a cooler attic. You will also have less chance of condensation and mold.
As a last measure of prevention, a waterproof membrane can be installed along the lower 36” edge of your roof. This underlayment is a peel and stick product that prevents the leaks associated with ice dams.
Following these guidelines will not only solve the root causes of ice dams, but it will save you money in wasted energy (conditioned indoor air), and ensure that your home is durable for many years to come.
Question about Ice Dams? Contact Post Remodeling for advice and a free in-home consultation!
