Bare spots in the attic insulation can cause temperature variations within a room below but are also a prime culprit for Ice Damming on the roof above.  Excessive heat transfers through the ceiling and up to the roof above.  This localized heat can cause the under-side of the snow pack on the roof to melt only to later freeze.  This cycle builds resulting in an Ice Dam.  Ice Dams damage shingles and can lead to leaks.  Under-insulated attics are often easy to address and can be a quick and cost effective improvement to your attic insulation problems.
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