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sidewalk with falling ice sign

Photo by the author

You may have noticed many “falling ice” signs around town. Personally, I recently counted five of them on my way to the coffee shop.

The icicles and falling ice are actually caused by ice dams, and the Building Science Corporation (BSC) and Massachusetts Department of Energy Resources have excellent articles on the subject. In general, ice dams are formed because snow that melts higher up on a roof re-freezes at the edge. The initial patch of ice creates a ‘dam’ that exacerbates the problem as more melted snow gets trapped. Ice dams are a problem for two reasons; they

  •  create icicles that are dangerous to pedestrians below
  • cause water damage to the building

    comkmercial building with icicles

    Source: Building Science Corporation

Each building is different and the specific culprit for ice dams will be unique to that building. The BSC article goes into detail on each of the following. But to summarize, there are four primary causes of ice dams:

  • Insufficient insulation
  • Air leakage
  • Heat sources in the attic space
  • Variation in snow thickness on the roof.

Fortunately, ice dams are a fixable problem. Here are steps that can be taken to address the problem:

  • Seal air leaks in your attic. Make sure your contractor does a good job on the air sealing BEFORE you insulate.
  • Insulate your attic to sufficient levels. Refer to the article for how much insulation you’ll need.
  • Re-locate and/or insulate heat sources above your attic insulation, such as ductwork and hot water pipes.
  • Install a proper moisture barrier to address snow melt that can occur even with properly insulated and air sealed attics.
diagram of mechnism behind ice dams

Source: The Building Science Corportion

Fixing ice dams not only makes the sidewalk safer and prevents water damage to your building, but it coincides with best practices for energy efficiency, so you’re likely to help control energy costs and improve the comfort of your home.

The statewide Mass Save® energy efficiency programs are designed to help businesses and homeowners upgrade their buildings to save energy and manage costs. For help tackling ice dams, contact Mass Save today for a home energy assessment or business services. Be sure to tell vendors beforehand about your problems with ice dams so they’ll pay extra attention to your roof and attic. You can sign up for your no cost assessment by visiting the Mass Save website, or calling 1-866-527-SAVE (7283).

For more information, contact Spencer Lawrence, DOER’s Zero Net Energy Building Program Manager.

Written By:


Zero Net Energy Buildings Program Manager

Spencer is the Zero Net Energy Buildings Program Manager at the Massachusetts Department of Energy Resources (DOER). At DOER, he manages the Pathways to Zero program, a $3.5 million initiative to facilitate a transition to the next generation of high-performance buildings. $3 million is being used to fund feasibility, integrated design, and construction of zero-net energy buildings in Massachusetts. An additional $0.5 million will be used for workforce development, public awareness, DOER resources, and other market development initiatives to help grow the zero-net energy industry.

Prior to joining DOER, Spencer worked as an energy auditor, identifying energy conservation measures for multi-family and commercial buildings across the country. Spencer is an AEE Energy Manager in Training (EMIT) and a Building Performance Institute certified Building Analyst (BPI BA). He graduated from Brown University with a degree in Political Science.

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