With all the snow, ice, melting, and freezing temperatureshomeowners in colder climates like Chicago have to worry about the potential for a back-up of water on the roofwhich can cause ice dams.

Ice dams are created after a heavy snowfall when the warm air in the attic causes the roof to warm and the snow to melt.  As it melts, the water runs down the roof toward the valleys and eavesonce it is there, it refreezes because the gutters, eaves and roof edges are colder, forming a mound of ice.  The ice traps the melt water forming ice dams, which are sometimes visible from the ground by the appearance of icicles on the outside of your gutters or eaves.  This trapped water can seep back up under the shingles or behind the fascia and soak throughinside you might see bulges in your drywall, blistering or peeling paint, mold, mildew, corroding fasteners, and as it sets, you may notice the walls and wood begin rotting. In addition even if the ice dams don’t leak inside your house they can tear off your gutters and loosen your roofing shingles.

Preventing Ice Dams 
The best way to stop ice dams from occurring is to have a cold roof. In most homes, heat escapes through ceilings into the attic and warms the wood and shingles directly above it.  Although the outdoor temperature is below freezing, the snow melts over the warmed sections of roof. When the melt water runs down the roof, it hits the cold edge not warmed by the attic. There it freezes, creating a rim of ice or ice dams. The key to preventing ice dams is simply to keep your attic and roof cold. After a snowfall, a cold roof will have a thick blanket of snow. A warmer roof, however, will soon have clear spots where the snow has melted off, and may have icicles hanging from the eaves.

How to Keep Your Roof Cold (besides preventing ice dams, by stopping air leaking into your roof you’ll save energy and reduce both your heating and AC bills):

1. Close up attic gaps and decrease heat loss
In the average home, about one-third of heat loss is through the ceiling into the attic. And most of that loss comes from air leaks caused by unblocked walls, gaps in drywall, and cracks around light fixtures, plumbing pipes, chimneys, access hatches and other ceiling penetrations. Air leaks can be tough to stop. You have to climb into your attic, pull or rake back insulation, and plug the leaks using foam, caulk and other methods. Low roof angles make some air leaks difficult to reach. This work is definitely a cool weather project; your attic will be unbearably hot otherwise. Always wear a dust mask, a long-sleeved shirt and long pants to help prevent skin irritations caused by insulation.

2. Measure your attic insulation level
While you’re in the attic, check the depth of your attic insulation. You should have about 12 to 14 inches of insulation in your attic.  Add more if you have less than 8 in. and have had ice dam problems in the past. Blown-in cellulose and fiberglass are usually better than hand-placed batt and roll insulation, because they fill more tightly around rafters, joists and other obstructions, leaving fewer gaps. It’s usually worth hiring a professional for this job; you probably won’t save much by doing it yourself.  Choose attic insulation with a higher R-value.  The higher the R-Value, the more insulation it provides. 

3.  Cap the Hatch
An unsealed attic hatch or whole-house fan is a massive opening for heat to escape. Cover them with weatherstripped caps made from foil-faced foam board held together with aluminum tape.

4. Increase ventilation
 Check with a roofing professional to make sure your attic has appropriate ventilation.  By keeping air moving, mold and mildew have a harder time growing and it keeps the air a consistent temperature. 

Heat cables can be mounted on the roof edge in a zigzag pattern and plugged into an outdoor GFCI receptacle. They’re ideal in spots where ice dams regularly occur and can’t be stopped any other way.  You’ll have to run the heat cable inside the gutters and down a downspout so the downspout doesn’t clog with ice.  This will increase your electric bill and should be installed by a professional electrician, however, they are very effective in preventing ice dams. We have many clients who have installed heat cables and been very happy with the result.

6. If you own a single story home
If you own a single story home, you can rake the snow off your roof after a heavy snowfall. A snow rake, which is an aluminum scraper mounted at a right angle on a telescoping aluminum pole, is the simplest solution for occasional heavy snows to prevent ice damming. If you pull the snow down, it can’t melt and form an ice dam. It’s an effective, if tedious, solution, but only for single-story homes.  Snow rakes should not be used on second floor roofs as you should never use a snow rake when standing on a ladder.  You can buy snow rakes at most major hardware stores or online.  WARNING:  If you are going to use a snow rake, you have to be extremely careful to not break your roof shingles which are brittle in cold weather.  

7. Flash Around Chimneys
Bridge the gap between chimney and house framing with L-shaped steel flashing held in place with unbroken beads of a fire-stop sealant. Using canned spray foam or insulation isn’t fire safe.

8.  When putting on a new roof

Another way to combat this issue is when you are in the market for a new roof.  Make sure your roofer puts in appropriate insulation and ventilation as mentioned above.  In addition, use a water-proofing underlayment under your shingles around the edges of your roof about 3 to 6 feet up from the roof edge. It can help keep heat inside the home, is resistant to water and is a great last line of defense against leaks so if there is backed up water, it won’t go into your home. It doesn’t prevent the formation of ice, but it will stop the water from seeping into your home.  Your roofer will then shingle over the top of the water-proofing underlayment.


Be careful to not:

1.  Climb up on your roof. This can be dangerous, especially when there is snow and ice on your roof.

2.  Put yourself at risk of carbon monoxide poisoning.  Make sure your combustion appliances (furnaces, water heaters, etc) are still venting to the exterior either through the roof or walls and aren’t venting to your roof or through the soffit when you work to make your home airtight.  Appliances and mechanicals that don’t draft properly can dump waste gases, including potentially deadly carbon monoxide, into your home so we recommend hiring a professional to seal up any leaks to make sure you’re doing it properly and not putting your family at risk.  

Making sure these precautions are followed will help alleviate the stress of a water mess inside your home during the winter months and should save on your heating and cooling bills. For more information about ice dams check out   https://www.irmi.com/term/insurance-definitions/ice-dams  or https://www.statefarm.com/simple-insights/residence/ice-dams-and-attic-condensation

What To Do If You See An Ice Dam On Your Roof
Ice dams themselves aren’t necessarily a problem unless they leak into your home.  If you don’t see any signs of damage or leaks then you may not have to do anything right away. Instead, during warmer weather apply the prevention strategies mentioned above.

If you do have leakage from an ice dam and can’t rake the snow off the roof, call your insurance company.  Water damage, ice dams and other winter weather disasters account for almost 20% of all homeowners insurance claims, according to the Insurance Information Institute.  If your insurance company won’t assist you, call a roofing company and see if they can steam it off.  A steamer is like a pressure washer, except the water is hot. It melts the ice away without damaging the roofing.  Do NOT chip the ice off with a hatched or ice pick as that can puncture the shingles.  Another option is to use calcium chloride ice melt to melt the dam yourself. Fill a nylon stocking with calcium chloride ice melt, typically sold at any hardware store. Place the nylon stocking vertically across the ice dam, and it will melt a channel in the dam through which water can flow. Make sure the channels extend all the way to the edge of the roof. We only recommend doing this if you have a one story home where you can easily reach the ice dam.  If you can’t easily reach the ice dam from the ground, do not climb on your roof as it can be very dangerous.  According to Consumer Reports, there were an estimated 1,600 emergency room visits between 2014 and 2016 related to homeowners attempting to remove snow from their roofs without professional help. 

Disclaimer: We are not roofing experts. Before implementing any of the above ideas, we suggest contacting your roofer or general contractor to have them asses what would be best for your particular home.  Ask them to conduct a blower door test to evaluate how airtight your ceiling is so they can determine the right course of action for your home. They also may use an infrared camera to find places in the ceiling where there is excessive heat loss.

This content is not the product of the National Association of REALTORS®, and may not reflect NAR's viewpoint or position on these topics and NAR does not verify the accuracy of the content.