For Immediate Release: January 4, 2008
It's That Time of Year: State Energy Office Offers Useful Advice Concerning Ice Dams
With warmer temperatures and the snow pack on many roofs, there is sure to be an increase in ice dams and icicles on roofs. The State Energy Office at the Minnesota Department of Commerce has information on the causes and solutions to these common problems, based on years of research and accepted building science.
A number of factors contribute to the formation of ice dams, including the hidden (but critical) air leaks that occur between the insides of our homes into the attic, a result of holes and gaps around plumbing and electrical lines, chimneys, and sometimes the tops of wall cavities. These air leaks act as mini-chimneys, pumping warm air into attic spaces, pushing thermal energy through the insulation, warming the underside of the roof deck and triggering the melt. The snow melt flows to the roof edge where the roof surface temperature is colder, and then refreezes creating an ice dam, often with icicles.
Aside from the potential damage to roof decks, eaves, gutters, and injuries caused by ice removal attempts, attic air leaks also indicate a significant loss of energy and are a source of cold drafts and potentially dangerous backdrafting of combustion appliances.
It is important to note that, despite popular belief, insulation materials like fiberglass or cellulose do not stop air leakage. In fact, if the air that leaks into the attic contains moisture, it can actually condense onto the insulation, reducing its effectiveness and potentially leading to damage caused by wet insulation and attic framing. This additional moisture in the attic can (wrongly) suggest the need for additional attic ventilation, which is merely treating the symptoms, not the source of the problem.
Many homeowners who add insulation and ventilation to attics see little reduction in ice dams. Other suggested remedies (such as removing the ice and snow, applying salt, or using heating cables) risk damage to the roof and do not address the real source of the problem.
An energy audit that includes a blower door test can indicate the possible existence of attic air leaks; further inspection can pinpoint exact locations and suggest proper remedies, including sealing the air leaks with expanding foam, caulking, or other sealants. This sealing should be part of every attic insulation job (often it is not!), and can be done even after an attic has been insulated.
Experts from the State Energy Office are available for background and on-the-record interviews regarding ice dams or other energy conservation topics, including information about how homeowners can ascertain whether they have attic air leaks or other energy-wasting issues.