Match the fan outlet and its required airflow. Reducing the duct diameter can increase noise and reduce extraction performance.
Duct Sleeves for Fans, Grilles and External Terminals
Wall ducts create a continuous air path between an internal fan or grille and the external terminal. MacBlair stocks duct components for through-wall ventilation, helping extract and supply systems cross masonry and lined walls without discharging into a cavity.
Match diameter and shape to the fan connection and required airflow. Long runs, tight bends and abrupt size reductions increase resistance, so keep the route short where possible. Measure the complete wall build-up and allow for a slight outward fall where the system calls for drainage.
Seal around the sleeve while keeping the duct bore clear. Coordinate it with cavity insulation and insulated internal lining to limit cold bridging. Use an external terminal suited to weather exposure, and select surrounding wall construction materials to maintain the fire and moisture detail.
Wall Ducts FAQ's
A rigid sleeve usually gives a smoother, protected route through masonry. Use flexible connections only where the fan system permits them.
Many through-wall extract ducts use a slight outward fall so condensation cannot run indoors. Follow the fan and terminal instructions.
Use a continuous sleeve and seal it to the relevant air, water and fire-control layers without allowing foam or mortar to block the bore.
Only with a system designed for combined airflow, backdraft control and commissioning. Separate ducts are often simpler and more reliable.