Why it matters

• Otsego's split between brand new subdivisions and older, established large-lot properties means the underlying cause of an ice dam can differ significantly from one Otsego address to the next, which is why the assessment matters as much as the removal.

• Poor attic insulation that lets heat escape and warms the roof deck from underneath.

• Inadequate attic ventilation that keeps the underside of the roof warmer than the outside air.

• Air leaks around recessed lights, attic hatches, vents, and chimneys that let warm household air reach the attic.

• Heavy snowfall followed by freeze thaw cycles which are common through a Minnesota winter.

• Roof design and older or worn roofing materials that let water back up under the shingles once ice has formed.

When it makes sense to act

• Sooner for Otsego's older, established properties. Aging attic systems on large-lot transplant properties are more likely to produce recurring ice dams than newer subdivision homes.

• As a diagnostic opportunity for newer Otsego subdivisions. An ice dam on a newer home is worth investigating specifically, since it usually points to a ventilation installation issue rather than a design flaw.