Does a metal roof need attic ventilation?
The need and method for ventilation come from the building assembly, not simply the roof covering. Many vented attics require clear intake and exhaust paths, while some engineered compact or unvented roofs use a different moisture-control strategy.
What affects the answer?
- Vented attic versus cathedral or compact roof
- Air sealing at the ceiling plane
- Insulation placement and continuity
- Indoor humidity
- Soffit intake and high-level exhaust
- Snow, wind and local code
What homeowners should understand
Ventilation cannot compensate for large air leaks from bathrooms, kitchens, light fixtures or attic hatches. Warm moist air should be controlled at its source and kept out of cold roof spaces. Exhaust ducts must terminate correctly rather than dumping moisture into the attic.
A roofing contractor should preserve or improve the intended ventilation path, but complicated assemblies may need building-science design. Adding vents randomly can short-circuit airflow or admit snow and rain.
Questions to ask your roofing contractor
- Is this roof designed as vented or unvented?
- Are soffit intake paths blocked by insulation?
- Are indoor exhaust fans vented outdoors?
The bottom line
Most conventional attics need a deliberate ventilation and air-sealing strategy. Determine the assembly first; do not rely on metal roofing to solve attic moisture.