Snow Signals Revisited

by Douglas Black, ENERSPEC, January 16, 2013

I first introduced parts of this blog in 2006 and even then I had  worked for 10 years with contractors who use blower doors, infrared cameras and a wide variety of other high-tech equipment to test for air leakage, improper insulation, and other home defects.   This allows them to diagnose home comfort problems and fix defects that will cause premature deterioration of the home. I have, on occasion, utilized much of this high tech wizardry myself.

Performing Blower Door test

Blower Door Test

With the help of a real climate-change winter, you can make similar evaluations without all the high-tech equipment. One of the first places to look for expensive, wasteful heat loss is into the attic. Planning next summer’s attic remodeling project to save money is not difficult, if you know how to “read the snow signals.”  It’s not rocket science, but let’s start with the basics –

Chilly Willie next to the Couch Cozies

Chilly Willie next to the Couch Cozies

A good sign is an even, continuous blanket of snow. There are no icicles visible. This attic is well sealed, well insulated, and ready to shelter this home for years of warm, comfortable homeownership. Our homeowners are cozy on their couch.

The Couch Cozies neighbors are not happy campers.  It’s safe to bet that their attic is completely uninsulated.  The only snow left on the roof is out on the eaves.

The massive icicles indicate that this home is very vulnerable to ice damming and roof leakage. That is, first some snow starts to melt, and freezes when it reaches the cold eaves. As the rest of the snow melts, and pools up as liquid water behind the frozen ice “dam”, it can seep between the shingles and into the roof cavity and wall.

Ice buildup under a blanket of snow.

Ice buildup under a blanket of snow.

Some homeowners express concern about the weight of this much snow on a roof. However, this snow does not need to be shoveled off. A structurally sound roof is built to handle at least 30 pounds per square foot of “live load.” It would take several feet of snow to create even a minor risk.


We insulate attics to keep HEAT from escaping the living space, and to keep the attic cold and dry. Most homeowners understand that. However, insulation is only half of the protection that a good attic needs. INSULATION DOESN’T STOP AIR FROM LEAKING, AND TAKING HEAT AND MOISTURE WITH IT. A HOME PERFORMS WELL ONLY WHEN BOTH HEAT AND AIR ARE CONTROLLED.

Heat escapes into attics in two major ways; by conduction and by convection. Conduction occurs when heat flows from warm materials to colder materials. Convection occurs when warm, moist air rises and leaks out of the living space, and carries heat with it. Typical attic insulation slows dramatically the conduction that is the primary problem. However, insulation does not plug air leaks and prevent convection. Convection, from uncontrolled air leakage can create significant problems, as in this home:

Air Leaks are the Problem Here

Air Leaks are the Problem Here

Air leakage into the attic can create other problems. If it happens in just small, concentrated areas, it can promote structural damage as well. In the home below, the air leakage is just in a small area around the sewer stack (the pipe sticking up.) Note how thick the ice is on the eaves, especially just below the pipe. Closer examination showed that the rain gutter is already damaged, and the shingles and decking under all this ice may be damaged, too.

In short, the snow on your home’s roof can tell you a lot about how the building is performing. Taking a walk through the neighborhood, to compare your home to others experiencing the same weather conditions, can be a very educational experience. If it helps diagnose defects that are affecting your home’s performance, it could be a very profitable experience, too.


Douglas Black

Douglas Black

Founder of ENERFICIENCY in 1999, Douglas Black  has analyzed and found positive energy solutions for a variety of projects ranging from low income housing to houses of worship, and from classrooms to courthouses.  Mr. Black was certified as a LEED Accredited Professional through the U.S. Green Building Council in 2008, and has served on many non-for-profit boards and committees.

Having more than 30 years experience in the green and sustainable building field, Douglas Black has dedicated the past 20 years to energy efficiency in the built environment.

Mr. Black is a high performance car enthusiast, always with an ear to the pavement for what’s fast and new.  He began blogging enerficiency On The Road in 2001, and now continues reporting from Auto Shows and Swap Meets at his Hot Flying Rats! blog –

He also uses his MagicEightBall to predict sporting outcomes and shares on his blog

Photography is a lifelong passion for Douglas Black, and while not capturing enthusiastic smiles at Wrigley Field he captures moments in the built environment.

And in his spare time, he works on getting that Captains License, expecting to retire on the water one day, taking photos.



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