Ice Dams

 

Which House Looks Like Yours in the Winter?  

 
Both of the pictures above were taken in January 2011, the worst month for ice dams in many years.  One home above has an air leakage control and insulation system installed in the attic.  Which one do you think it is?    

Garret and Erin, the owners of the home on the right, worked with B|E Retrofit to prevent ice dams and save energy in 2010.  The solution at Garrett and Erin’s house works because its design is based on building science and it was installed with high-quality workmanship and attention to detail.  

You have landed on this page to study ice dams. We will first describe what causes an ice dam, second we will debunk some common New England ice dam “solutions,” and then discuss proven strategies that can be used as guidelines to solve ice dam problems for every style of roof and attic design.

What Causes an Ice Dam?

Ice dams are a result of excessive heat loss out of a building.  It is that simple.  On a day when it is below freezing and heat reaches the underside of the roof surface, snow will melt.   

What is the source of heat to melt snow on a day when it is 20°F outside?  The answer: the 60°F - 70°F temperature in the living space of the house that is directly below the roof.  

When heat from the house reaches the underside of the roof deck and melts snow, the water flows down the roof towards the eaves by gravity and then at the eaves (outside of the heat source of the living spaces below), the water refreezes.  As this process continues throughout the winter, your ice dam grows.  

The only way to stop this process is to block the heat leaving the living space from reaching the underside of the roof deck and melting the snow on the roof.  If snow melts on a day when it is below freezing, it will refreeze at the eave.

Traditional “Solutions” Treat Only Ice Dam Symptoms  

The common “solutions” that homeowners are most familiar with only treat the symptoms of ice dams, not the cause:

• Metal Slip Surface at the Eaves – a “slip” surface is intended to get snow and ice to slide off of the roof.
• Electric Heat Cables – after energy was already wasted once, by allowing it to leak out of the living space, heat cables use more energy in an attempt to melt away the sheet of ice.
• Salt Socks – this was a new one for us last winter.  Homeowners used pantyhose and sodium chloride to “cut” streams in the ice sheets at the eaves to allow water to leak off of the roof.

Many contractors also recommend “solutions” that don’t get at the root cause of the problem:

• Ice and water shield roof underlayment – many roofers recommend a waterproof roof underlayment.  A layer of rubber will not stop heat loss from melting snow.  A roof with a waterproof membrane will still have ice dams because this rubber underlayment is not solving the cause of the problem.
• Attic ventilation – roofers also recommend adding more ventilation, at the ridge and soffit.  Attic ventilation is intended to exhaust warm air to the outside after it has reached the attic.  Again, this approach is trying to solve the problem after it has already started.  Ventilation can exhaust small quantities of warm air, but it will not solve all ice dam problems. 

Unfortunately, homeowners will continue to chase ice dam problems and roof leaks every winter after choosing any of the options above.  Roof rakes and roof shoveling will continue to be important parts of the winter chores if a homeowner selects one of the options above.  

The only approach that can stop ice damming is to prevent the first step in the cycle: stop the heat from the house from reaching the roof surface.  

Every Home Can Be Fixed 

The approach to solve ice dams is straightforward: identify the pathways and sources that feed heat to the roof deck and then block 100% of them.  This approach will take different forms, but it can be designed and implemented to fit every style of home construction. 

The three most common ways that heat reaches the roof deck are:

1. Air leakage pathways that connect the attic with the warm spaces in the house.  Common air leakage pathways are: attic access hatches and pull down stairs, large gaps around the plumbing and electrical chases, recessed lighting and cracks above the framing of interior and exterior walls.
   
   WARNING: DO NOT SKIP THIS STEP
   
   No amount of insulation will solve ice dams without first blocking the air that is leaking into the attic.  Air will blow right through fluffy, air permeable insulation like a breeze through window curtains.   Air leakage control and draft-stopping are done with caulks, foam sealants and rigid materials that block air movement, not fluffy, air permeable materials like fiberglass.
   
   
2. Inadequate insulation levels that allow heat loss through the top-story ceiling.  Stopping heat loss through building materials (conduction) is the part where we add insulation.  After the air leakage pathways are completely blocked, and only after 100% are blocked – the more insulation the better.  
   
   
3. A heat source below the roof surface is a sure way to end up with ice damming.  The heat sources that we see most in attics are: heating equipment, air handlers, duct work and recessed lights.  Heat sources in attics pose a big challenge.  

Every Home is Different 

The location of the air leakage control and insulation systems is dependent on the construction of the home.  B|E Retrofit understands that every building is different, so we custom design solutions for each individual home.   Barriers can be built at a flat ceiling surface or directly in contact with the underside of the roof surface.  

As noted above, the principles of ice dam control are simple, but designing projects in existing buildings is challenging.  This is why understanding the science behind each project is critical.  B|E Retrofit has studied and worked with North America’s leading building scientists and engineers to design and install solutions for our clients.  Our expertise and relationships ensure that every project is a success.

Working with B|E Retrofit

B|E Retrofit is known for executing smarter and deeper home energy retrofits than our competitors.  A smart retrofit is designed using building science principles, consistent with the complex flow of heat, air and moisture in a home. 

Understanding these forces leads to a retrofit that improves the health, comfort, durability and energy efficiency of your home.  A deep energy retrofit is a project that pursues aggressive levels of total energy savings.  An ice dam prevention project can be an excellent way for a homeowner to consider the benefits of a deep energy retrofit that can lead to 50% - 90% total energy savings.  

Join our growing list of clients that have eliminated ice dams once and for all.  We are proud of the work that we do and the relationships that we create with our clients.  We are happy to connect any interested homeowners with our network of satisfied clients. 

Please call or email us today to eliminate ice dams once and for all.   You can also visit us on Facebook to learn more

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