Flexible Ducts

The correct flexible duct diameter depends on the CFM (cubic feet per minute) airflow required. As a general guide: 4" flex duct handles about 40–60 CFM, 6" handles 100–120 CFM, 8" handles 160–200 CFM, 10" handles 275–350 CFM, and 12" handles 400–525 CFM. We offer flexible air duct from 3" to 24" to cover residential and commercial needs. For exact sizing, refer to our flex duct CFM chart or flex duct sizes guide.

HVAC industry best practice limits flex duct runs to 25 feet maximum, and shorter is always better. Every extra foot adds friction loss — flex duct has roughly 50% more friction than rigid duct of the same diameter. Keep runs as short and straight as possible, avoid sharp bends, and pull the duct fully taut. Runs over 14 feet should be upsized one diameter. See our flex duct installation guide for detailed best practices.

Aluminum flexible duct uses multi-ply aluminum foil and handles temperatures up to +120°C (+248°F), making it the industry standard for supply and return air. Polyester flexible duct is lighter and more budget-friendly, rated to +100°C (+212°F), and works well for general ventilation. Aluminum is preferred where fire rating matters (UL 181 Class 1), while metalized polyester is popular for high-volume residential projects. We also offer PVC combi ducts that combine both materials for moisture-resistant applications. Compare options in our flex vs rigid duct guide.

Standard aluminum foil flex duct should NOT be used for dryer venting — building codes require semi-rigid or rigid metal duct for dryer exhaust because lint buildup in flexible walls creates a fire hazard. Our semi-rigid aluminum duct (rated to +400°C / +752°F, UL 2158A listed) is specifically designed for dryer venting. It holds its shape after bending and has a smooth interior that resists lint accumulation. Check our dryer duct guide for code requirements.

Yes. We manufacture PE (polyethylene) flexible duct in both transparent (clear) and opaque versions, available in diameters from 50mm to 600mm (2" to 24") and roll lengths up to 150m per roll. PE duct is corrosion-proof in saltwater and marine environments, making it ideal for ship ventilation, bilge air systems, offshore platforms, and port supply chains. It is also widely used in food processing, pharmaceutical, and chemical plant ventilation where the absence of plasticizers (unlike PVC) and chemical inertness matter. See our PE flexible duct marine guide for full specifications and sizing tables.

Yes. Our aluminum and metalized polyester flexible ducts are UL 181 Class 1 listed for use in air duct systems. Our semi-rigid aluminum duct carries UL 2158A listing for dryer venting. All products meet or exceed ICC/IECC mechanical code requirements. We provide UL test reports and compliance documentation with every bulk order. With 28 years of manufacturing experience and a warehouse in Houston, TX, we ensure every product meets North American standards.