The cause of ice dams on the roof can be explained in two words – excessive attic heat. Excessive attic heat causes some areas of the roof to be warmer than others. The result is that the snow on the roof melts unevenly, usually leaving huge chunks of ice intact along the roof edge but with melted snow behind. The snow obstructs the melted ice from draining naturally from the roof, essentially creating pools of stagnant water known as ice dams.
What Causes Excessive Attic Heat?
The issue of why specifically the attic is getting hot is a separate one and can be chalked to multiple factors, sometimes two or more working together to create a warm attic and consequently ice dams on the roof. Under ideal conditions, the attic temperature should be no higher than 15 degrees of the outside temperature.
Some of the reasons for excessive attic heat include:
Air Leaks: warm air naturally rises and will find its way in the attic if there is room to pass through. Gaps into the attic usually caused by insufficient or improper attic insulation cause this warm air to get into and settle in the attic. The attic temperatures eventually exceed the external temperatures increase the chances of ice dams.
Poor Duct Work: poorly sealed and improperly insulated ductwork and air vent lines in the attic can increase the attic temperature significantly by leaking hot air into space. The ducts also heat up as you warm your house in winter further contributing to increased attic temperatures. Poorly insulated ducts in your attic are similar to having heater coils in the crawl space. Shoddy joints and poor seals on your air handlers equally leak hot air into the crawl space.
Furnace in Attic: although some homes can get away with installing a furnace in the attic, this is one of the major causes of ice dams where one is present. Space constraints and multiple-zone HVAC units cause homeowners to install a furnace in the attic. It is easy to see why this situation can increase attic temperature beyond the desired threshold and cause ice dams. As a rule of thumb, don’t install a furnace in your attic.
Poorly Ventilated Attic: as previously mentioned, the desirable attic temperature, especially during winter, is within 15 degrees of the outdoor temperature otherwise you risk ice dams. Proper attic ventilation allows for cool air to circulate freely and keep the temperatures manageable. Although some homes can do with one or two windows open in the attic to allow cool air, proper attic ventilation including installing free-flowing soffit vents and/or adding ridge or roof vents can help to keep the attic temperature in check.
Intricate Roof Designs: sometimes the major problem is the architecture itself especially if construction didn’t account for the area’s climate. Intricate roof designs can dump snow from higher levels of the roof to the lower levels rather than on the ground. The design may also prevent the snow from sliding off naturally. Add excessive attic heat to the picture and ice dams are going to form.
Getting Rid Ice Dams on Your Roof
Attempting to remove the snow is only a temporary solution that doesn’t address the problem of why the ice dams are forming in the first place. It is also rarely obvious why your attic is getting too hot especially where there are multiple factors contributing to the problem.
Call Attic Insulation Toronto for a thorough inspection and expert recommendation and repairs. We may be able to do many of the necessary repairs during winter or at the very least, manage the problem sufficiently until proper work can be done during spring or summer. Call us to book an inspection: 647-931-6385.