Ventilation & Attic Systems Flashcards

Which of the following roof designs presents the greatest challenge for installing continuous ridge ventilation?

Answer: Hip roof

Hip roofs have short ridge lines relative to their footprint, making continuous ridge ventilation more limited and requiring supplemental exhaust options.

What is 'net free area' (NFA) as it applies to roof ventilation products?

Answer: The actual open area through which air can freely pass, excluding obstructions like mesh or louvers

NFA is the unobstructed area through which air passes, accounting for restrictions from screens, baffles, and louvers that reduce effective airflow below gross vent size.

When a GAF contractor inspects an existing roof for ventilation adequacy, what is a key indicator of long-term moisture damage caused by poor ventilation?

Answer: Cupping or buckling of the roof deck sheathing

Cupping or buckling of OSB or plywood roof decking is a telltale sign of chronic moisture exposure caused by condensation resulting from inadequate attic ventilation.

In a properly designed attic ventilation system, where should soffit intake vents be positioned relative to exhaust vents?

Answer: At the lowest point of the attic space, as far below the exhaust vents as possible

Soffit intake vents should be at the lowest point of the attic (at the eave), maximizing the vertical distance from ridge exhaust vents to create the strongest thermal buoyancy-driven airflow.

Which GAF ventilation product is specifically designed for installation on roofs where there is no overhang and soffit intake ventilation is not possible?

Answer: Cobra® IntakePro® Shingle-Over Intake Vent

GAF's Cobra® IntakePro® is a shingle-over intake vent installed on the lower slope of the roof, providing intake air when no soffit or overhang exists.

What is the recommended minimum distance between the top of attic insulation and the underside of the roof sheathing in a rafter bay, according to industry best practices?

Answer: 2 inches

Industry best practice and most building codes require a minimum 2-inch clear airspace between the top of the insulation and the roof sheathing to allow unobstructed airflow.

A GAF-certified contractor is replacing a roof and discovers that the existing off-ridge exhaust vents are located only 18 inches below the ridge. What is the primary concern with this placement?

Answer: The short distance from the ridge may allow exhaust vents to act as intake, drawing hot ridge air downward

Off-ridge vents placed too close to the ridge can function as intake vents instead of exhaust, drawing already-hot air from near the ridge rather than from the soffit area.