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When a vent is less than 10 feet high, the vent should be at least as large as the flue collar outlet.b) Vents for draft hoods or flue collars 12 inches in diameter or less should NOT be reduced more than one pipe size.
All Pop Vent Roof Louver Models by Diameter and Collar Size. Note: 1 Collar vent models for Pitched Roof applications. Excellent on Steep Slope Roof Applications. Active Ventilation Products' Pop Vent also known as the Roof Louver is an excellent roof vent for ventilating attic spaces on steep slope roof applications. The Roof Louver will add necessary roof top ventilation to alleviate moisture from the attic in the winter and heat in the summer.