Flexible duct can simplify connections where rigid ductwork would be awkward. Its performance depends heavily on the installed shape. Excess length, tight bends and sagging can add resistance and reduce delivered airflow even when the nominal diameter is correct.
Measure the route, not only the straight distance
Provide the connection sizes and the route needed around obstructions. Avoid unnecessary surplus length that must be compressed or folded into the ceiling space. Use the manufacturer's bend and support requirements rather than forcing the duct around a sharp corner.
The Air Duct Council publishes installation guidance for flexible ducts. The practical principle is to preserve the intended internal air passage through appropriate extension, support and connection details.
Insulation and vapour protection do separate work
Insulation limits heat transfer; a correctly sealed outer vapour barrier helps control moisture reaching cold surfaces. A torn jacket or poorly sealed connection can allow condensation even when the insulation thickness appears adequate.
Specify the inside diameter separately from the outside insulated size. Ceiling space must accommodate the full assembly, including bends and supports, rather than only the air opening.
Confirm the classified product and intended service
Air ducts and air connectors may have different use restrictions. Where a fire or safety classification is required, obtain evidence for the exact product and installation conditions. A familiar “Class 1” phrase should not be treated as proof of every required property.
Ordinary ventilation flex should not be assigned corrosive process exhaust, hot gases or abrasive dust without a suitable design and product evidence. Select lining, temperature limits and pressure capability for the actual air stream.
After installation, assess airflow and connections as part of system commissioning. Increasing fan speed is not the first remedy for a crushed or unnecessarily long flexible branch.
Send the diameter, route and air conditions to shengtongJH to coordinate duct construction, insulation and connection options.