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Post insightRoof ventilation failures cause more shingle damage than hail in most climates
Insufficient attic ventilation traps heat (up to 150°F in summer), cooking shingles from below and voiding manufacturer warranties. Per IRC R806.1, attic ventilation requires 1 sq ft of net free area per 150 sq ft of attic floor. Balanced intake (soffit) and exhaust (ridge) is critical. Mixing exhaust types (ridge vent + power fan) short-circuits airflow. Fix ventilation before replacing shingles or you void the new warranty too.
Ice dams are an insulation problem, not a roofing problem
Ice dams form when heat escapes through the roof, melting snow that refreezes at the eaves. The fix is not heat cables or ice-and-water shield (those are band-aids) — the fix is air sealing and insulating the attic floor to R-49 or higher per IECC 2021. Seal all attic penetrations (can lights, plumbing stacks, electrical boxes), then blow in insulation to code depth. This eliminates the heat source that creates dams.
Ice and water shield goes under the drip edge at eaves, over it at rakes
The correct installation sequence per manufacturer specs and the NRCA Roofing Manual: ice and water shield directly on decking at the eaves, metal drip edge installed over the shield. On rakes (sloped edges), the drip edge goes over the underlayment. Reversing this sequence at the eaves allows capillary action to wick water backward under the metal, rotting fascia boards.