I remember the fun of breaking off icicles along the roofline of my childhood home and eating them like a popsicle. I thought the were beautiful the way the little bubbles of ice froze inside and glistened in the winter air. Now I know, those icicles can be one sign of a bigger problem: an ice dam. This is where water in the gutters freezes, causing a dam for water thawing and coming down the roof behind it. With no where else to go, the water sometimes ends up in the attic.
Snow or rain can cause big problems in attics if insulation, ventilation and caulking, or sealing, is not installed or maintained correctly.
In colder climates, ice dams, thick ridges of solid ice forming in the gutter or in the eaves of a home, can damage gutters, siding or walls, if left uncontrolled. Ice dams are caused when warm air flows into the attic and can't escape.
The warm air warms the roof, melting the snow above. Snow melts, and the melt off runs down the roof to the eaves. Colder temperatures lower at the eaves cause the water to refreeze. Eventually, the ice forms dams in the gutters. Water flowing down the roof backs up under the shingles and can flow from there into the attic or interior wall spaces. Wet insulation or framing members can reduce R-values, lead to possible mold and mildew problems or damage interior finishes.
In warmer climates, mildew and mold can still be a problem if warm moist air coming up from the house isn't properly vented outside. Excessively warm temperatures in the attic can weaken components of the roof and shorten the lifespan of roofing material. Make sure all appliances in the home vent outside and soffit vents are kept clear of insulation and other debris. This allows cooler air to come in at the bottom of the roofline and push warmer air out the top.