Ice Dams can cause very serious and expensive to fix problems, and are usually caused by improper ventilation of your attic space and inadequate insulation of your roof. Ice Dams are a sign of heat loss in the attic, and this lost heat is money you throw out the window.

Ice dams may seem harmless at first, but they are known to cause thousands of dollars in roof leaks, structural  damages and repairs of your home. The can also create dangerous mold growth, which can cause or aggravate allergies, asthma and other respiratory diseases.  Fighting ice dams can be costly, and you also need to know how to approach the problem to make your efforts more efficient so that you can permanently eliminate them.

This Ice Dams Prevention Guide will help you identify Ice Dams and eliminate either sources of the problem (preferred method, though not always feasible) or the effects, which are just as dangerous for you home.

What are Ice Dams?

If you live in Northern US, Canada, or any other region with cold winters and lots of snow, you’ve seen and possibly experienced first hand Ice Dams – large ice formations along the eaves of the roofs. Although ice dams are common on most roofs in the northern regions of US and Canada, they cause most damages and leaks to Low Slope roofs, as it is much easier for water to “travel” up a low pitch roof vs. a steep roof.

Additionally, you may see many roofs in New Hampshire, northern Massachusetts, as well as other parts of the country with 2 x 2 feet aluminum pans locked together along the eaves of the roof. These metal sheets are installed so that ice formations would slide off, and ice dams would not build up. This may work for steep roofs, but on a low slope, the ice dams can form in the center of the roof as there is not enough pitch for water to run off.

Just a few of the most common ice dam related problems include roof leaks, rotted roof decking / exterior & interior walls / framing, mold and related respiratory illnesses (allergies, asthma, etc.), reduction in insulation effectiveness and associated heat-loss.

What Causes Ice Dams?

Massive Ice Dams on Low Slope (Shed Dormer) Roof

The main causes of ice dams are poor ventilation and / or inadequate insulation in the attic. When it snows outside, a thick layer of snow settles on the roof, and the warm air from the attic slowly melts the snow. Melted snow begins to run down the roof toward the eaves, which are usually colder than the rest of roof surface. There, water freezes, thus creating ice dams. As more and more water melts at the top of the roof and freezes at the bottom, ice dams grow to a thickness of over 4-5 inches.

As ice dams become larger, and more melted snow water runs down the roof, it hits the already large ice dams and can not go down any more. At this point it starts to refreeze under the shingles. At the same time, warm attic air melts the newly formed ice under the shingles, which starts to drip inside the attic and /or down the walls.

Even if you have a very well insulated attic, which blocks most of the warm air from escaping your living space, still, some warm air will escape into the attic. This is where you need a working ventilation system, which will vent most of the warm air from the attic and will create temperature parity between outside and inside the attic. Only then, the snow will not melt artificially, and will not create ice dams.

Today, the most effective and commonly used attic ventilation system in residential construction and roofing is the Soffit / Ridge vent system. Although soffit/ridge system is the best-performing type of ventilation, it is not always possible to install it. While installing a good ventilation system on a new construction home is easy, some of the older homes were designed to have no ventilation at all, or optionally were build with two gable vents that are usually two 12 x 18 inches openings at the peak of the gable-side walls. These are not as effective as ridge and soffit vents but still work O.K.

In many cases however having a ventilation system is not an option due to many reasons, such as financial constraints or building limitations. For example, if a home was build with insulation stuffed between the roof rafters, but the the builder did not install baffles, which would create an air pocket to allow the flow of air. In this case no ventilation system will work, as there is no room for air to circulate. Of course, this situation can be fixed, but it would cost a lot of money and many homeowners are unwilling to spend that much.

Other types of roofs that are not designed to accommodate effective ventilation systems, such as ridge / soffit vents or gable vents, are Hip Roofs and low slope roofs. In the case of hip roofs, you could get away with static box vents or power vents with a thermostat. These are not as effective, but still provide some ventilation.

In the case of low slope roofs, builders and roofers not only need to solve the ventilation problems, but they also have to make sure that there are no leaks caused by the air vents. Unfortunately, too many builders and roofers do not include any ventilation on a low slope roof, as it is easier for them to avoid potential leaks. For example, a ridge vent on a low pitch roof will allow the wind driven water to enter the attic.

Since most low slope roofs are not vented, ice dams are much more likely to occur and cause extensive damages to the roof and the interior of the house, as it is a lot easier for water to travel “upward” on a low pitch roof. Most low slope and flat roofing systems are designed to have their seams put together with glues and adhesives, ranging from solvent based seam lap adhesives used with EPDM black rubber to Tar and roof cement used with asphalt and modified bitumen roofs. Du to the nature of adhesives, these roofs are prone to develop leaks, as adhesives break down with time and weather affecting their longevity. Ice Dams only speed up the process, as the ice melting and re-freezing process expands the gaps between the seams.

Additionally, asphalt shingles are often used on low slope roofs, which is blunt ignorance on the part of homeowners, who did not do the due diligence, and hired a roofing contractor to install such a roof, as well as homeowner abuse by shady roofing contractors, who do not let their client know that the roof they are about to install violates manufacturers installation guidelines and annuls the warranty on the roof. By definition, a low slope roof has a pitch pf less than 3, while ALL shingles manufacturers require at least a pitch of 3 to install their asphalt shingles product.

In many cases, homeowners with low sloped roofs, turn to heated electric cables to melt the ice dams. Despite common opinion that heat cables solve ice dam problems, it could not be further from truth.

First, just a reminder that ice dams are caused by hot air escaping your living space and lack of adequate ventilation. Heat cables use electricity to melt the ice formations. Therefore, you are trying to fight a heat / energy problem by throwing more energy into the cold atmosphere, so instead of fixing the problem you just add a band-aid, which does not even work. At the same time, you incur ever increasing energy expenses, while the problem not only remains there, but becomes worse.

Heat cables melt ice dams along the eaves, but there are still ice dams forming just above the effective range of heat cables, so your ice dam leaks now occur high up the roof slope, affecting more insulation and aggravating the problem even more.

Permanent Solution to Ice Dam Problems

The best thing you can do to eliminate ice dams is to improve your attic ventilation and add / improve insulation to minimize heat loss.  Insulation should be your first step, as poor attic insulation is the main cause of ice dams, and besides, you don’t want to keep wasting your money on heating up your unused attic. Seal the gaps between insulation, use expandable foam insulation for tight spots, etc. If you have the soffit vents/air intake slots, make sure that loose insulation does not block the air circulation.

Install proper ventilation. As mentioned before, soffit and ridge vent system is most effective, and does not cost a lot if you are having a new roof installed. You can also add it to an existing roof, but make sure there are appropriate conditions for adequate air circulation. Do NOT mix different ventilation systems – if you do so, there is a good chance that one system will minimize the effects of the other, therefore your ventilation will stop working.

What To Do If You Cannot Improve / Fix  Ventilation and Insulation Issues

Although it is best to eliminate the source of the problem – heat loss and improper ventilation, it is not always a viable option for many homeowners, and another solution is required. As I discussed earlier, heat cables do not work and only increase your energy expenses. The best solution for a sloped roof is to have a Metal Roof installed.

Metal roofs are designed to eliminated all damages associated with ice dams, by preventing the water from traveling upward. Be it a standing seam metal roof or an interlocking shingles system, Ice formations may occur, but the design of the roof will not let the melting water rise and penetrate the roof surface.

In fact, due to their smooth surface, metal roofs shed ice and snow, which comes down like an avalanche. To prevent this snow from damaging things below and falling on someone’s head, special Snow Guards must be used, which you can see in the image above.

For low slope roofs, we install an IB roofing system, which features hot-air welded seams to prevent water from entering the roof, and is perfect for residential low sloped roofing, as it comes with an asphalt shingle pattern to give it an architectural look and design.

To properly ventilate a low slope roof, we’ve created a special assembly method, which allows the installation of ridge vent, and eliminates associated roof leaks. We raised a ridge vent by 2 inches from the roof surface. This clearance is more than sufficient to prevent any water from entering your house through the ridge vent.

In conclusion, I will once again mention that it is best to go to the source of the problem and fix as much ventilation and insulation as you can. Combine a great, energy efficient attic insulation with a permanent, cool flat or metal roof, and you will get a long lasting, great looking roof that will not leak, will save you money on roof repairs and heating / cooling costs, and take away many headaches of being a proud homeowner, as well as allow you to enjoy your home without ever worrying about roof leaks.

If you live anywhere in Massachusetts, Rhode Island or Connecticut, contact us to get a free roofing price quote and schedule a roof inspection and estimate to install a lifetime flat IB roof or a beautiful metal roof. You can also use our online roofing price calculator to estimate your roof replacement costs and annual energy savings.

References and Resources:

• Flat Roof repair guide, which includes cost estimates for basic and advanced repairs, as well as what you can expect and how to choose a roofing contractor to fix your roof. Useful information for DIY homeowners, property maintenance personal and business owners.