US Duct's Sept 2026 DuctQuote Update Accurate BOMs: Corrected counts for flanged pipes and four 3-inch 45-degree elbows. Smoother 3D Modeling: Fixed model loading, height stability, and locking, while cleaning up loading bugs and keeping movement handles active on "Place on Floor." Faster Management: Resolved search issues (including apostrophe searches) and sped up layout order loading.
Flap Exhaust Valves (Flap Stacks)
A resourceful after-the-fan product, flap exhaust valves, or stacks, are designed to open, like bird wings, with the airflow and close when the system is not exhausting. The lightweight and balanced blades produce minimal resistance to exhaust. The design of the housing and blades channel rainwater away from the opening and allow it to drain without intrusion into the ducting.
- Available in 4" to 32" diameter (contact for custom sizes).
- Also known as a winged stack.
- Diameters are +/- 1/8 inch.
- Alternative Solutions: No-Loss Stack, Jet Cap, Rain Cap
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