Circular ducting is the most cost-effective to manufacture, offers lower air resistance than semi-circular ducting, and is the preferred choice for centralised ventilation systems wherever installation space allows.
Ubbink Air Excellent AE34C is the smallest circular semi-rigid duct in our Air Excellent range, with a 75 mm outer diameter, designed for high-performance centralised HRV and ERV systems.
For optimal system design, recommended practice is to keep air velocity below 3 m/s to minimise airflow noise. The AE34C is sized specifically to meet this requirement, delivering up to 34 m³/h at 3 m/s, which is reflected in the product name.
Compared with larger 90 mm ducts, the 75 mm AE34C is easier to route and conceal within ceiling cavities, walls, and floors, making it well suited to space-constrained installations. However, the smaller diameter results in higher air resistance, so in applications requiring higher airflow rates or longer duct runs, two 75 mm ducts may be required where a single 90 mm duct would otherwise suffice. This approach maintains low air velocities and noise levels while offering greater flexibility in duct layout and installation.
The result is a cleaner installation, reduced pressure loss, and improved acoustic performance in well-designed ventilation systems.
