Thermal Bridging on Lee's Summit, MO Roofs

Thermal Bridging on Roof

 After the last show event in Lees Summit, I went out into the neighborhood and snapped some pictures to illustrate some common roofing problems you may want to address with your roofing contractor next time you need a new roof.  You may want to look at your own roof and snap some photos even if you don’t need a new roof, because you eventually will and this data is perishable and will be long lost when you eventually replace your roof.

 See the lines on this roof?  Why is it that the snow melts and leaves a pattern of perpendicular lines?  This is called “thermal bridging” and illustrates the location of individual framing members.  This pattern would be particularly pronounced for light-gauge steel framing (which may have been used in residential construction prior to steel prices increasing), but is still visible in wood-frame construction.  Since the insulating value of you framing members is less than the insulation, each framing member acts as a thermal bridge directly to the outside.  This provides a conduit to transfer or leak heat, which melts the snow into this interesting pattern.  Note on the left side of the photograph where this doesn’t happen?  Same roof slope, same sun exposure, the difference is that the left side is the roof over an unheated garage; minimizing the heat escaping into the attic and also the thermal bridge from the roof framing.

 In the Lees Summit locale, this generally isn’t or doesn’t lead to a roofing problem.  If the pattern is reversed however, where the snow melts between the roofing members, this indicates too much heat loss and can lead to ice damming.

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