Ice Damming and the Practice of Building Science

Contrary to popular belief, ice dams and icicles are not usually a roofing issue. Sure, roofers will add a layer of rubber under your shingles to keep the "ice dam lake" from running back up under your shingles
and into your attic, but it doesn't solve the problem. There is still a block of ice forming at the eaves of
your roof and large icicles are still pulling on your gutters and downspouts and worse is that ice dams
and icicles are a clear sign of energy loss. For all practical purposes, you are blowing heat (and money)
out of the top of your house into an already warming atmosphere.
Enter the practice of basic building science where the house is looked at as a system. Yes, warm air
generally wants to rise in a house. How is warm air working its way up into my attic? Where are the cold
drafts entering in the low areas of the house in this air exchange process?
When you start thinking about these two questions you are thinking like a building scientist and at the
heart of the ice damming and icicle solution.

Certainly attic insulation helps to keep your attic a cold buffering space between you and the outside,
but proper whole-home air sealing is where the science shows the biggest return on investment. For
this reason Focus on Energy offers higher rebates on air sealing at a higher rate than other
weatherization projects. They know that it will provide the most energy savings per dollar spent.

Focus on Energy Trade Allies know good air sealing work starts in your attic to seal the attic hatch and
seal top plates of the interior walls. Pushing your existing attic insulation aside exposes gaps and holes
to the attic for pipes, ducts, and wiring, all of which should properly air sealed. The chimney chase
should be sealed off with metal flashing and fire-caulk to create a fire block and seal it off from the
floors below. To complement this attic work, one must go into the basement and push fiberglass
insulation aside in the sill box cavities to look for utility penetrations for pipes, ducts or wiring that allow
cold air to flow into the house making downstairs floors feel cold.

All this, in addition to a thick blanket of insulation in your attic, keeps your attic cold and the living
spaces below warm. Instead of your snow melting and forming ice dams and icicles on those cold winter
days, you should have a blanket of snow resting peacefully on your roof.