Roofing fundamentals
Roof Ventilation and Why Most Colorado Attics Are Wrong
Most older Colorado attics are under-ventilated. Replacing the roof without correcting ventilation locks in the next 20 years of moisture, ice damming, and shortened shingle life, and almost universally voids the manufacturer's shingle warranty under GAF, Owens Corning, CertainTeed, and Malarkey terms.
How attic ventilation actually works
Air enters at soffit intake vents and exits at ridge or off-ridge exhaust vents. Balanced means roughly equal intake and exhaust net free area, with intake equal to or greater than exhaust. Imbalanced ventilation is worse than no ventilation at all because it can pull conditioned air out of the living space through ceiling penetrations.
The IRC and Colorado-adopted codes require 1 square foot of net free vent area per 150 square feet of attic, or 1 square foot per 300 square feet with balanced intake and exhaust and a vapor retarder, with intake equal to or greater than exhaust.
What goes wrong on older Colorado roofs
Painted-over soffit vents, blocked baffles in attic insulation, and undersized exhaust are the three most common faults. All three are correctable during a re-roof. Adding intake or soffit ventilation typically runs $300 to $650; a continuous ridge vent in a re-roof runs $900 to $1,200.
Why ventilation matters for the warranty
Ventilation problems (curled shingles in localized hot bands, frost on attic sheathing in winter, ice dams) almost universally void the manufacturer's shingle warranty. A bid that does not include an intake-and-exhaust ventilation plan is incomplete, even if the shingle is Class 4.