Ducting is the part of a ventilation system people spec last and regret first. A fan rated for a given airflow only reaches it through smooth, short, sensibly sized duct. Every bend, every metre of flexible duct and every reducer costs airflow, and undersized ducting turns a quiet fan into a loud one.
This section covers insulated and acoustic duct, PVC combi duct, flexible and nude duct, Y pieces, reducers, clamps and jubilee clips, from Seahawk, Can-Fan, Can-Filter, Blauberg, Phresh and Holland Forge. Prices run from about $2 for a clamp to $155 for insulated runs, with most items around $36.
What actually matters. Match the duct diameter to the fan rather than to the space you have; stepping a 200 mm fan down to 150 mm duct throws away the capacity you paid for. Keep runs short and bends gentle, because a sharp 90 degree bend can cost as much airflow as several metres of straight duct. Acoustic and insulated duct is worth it where noise or condensation is a problem, which in a bedroom or garage is usually both.