Aluminium Foil Flex

Aluminium foil flexible ducting — the standard flexible duct of HVAC installation — supplied in generous 10m lengths and 16 diameters from 80mm to 500mm. Choose between two versions: plain uninsulated foil flex for general connections, and insulated foil flex with a wrapped insulation layer for runs where heat loss and condensation matter.

Insulated or uninsulated?

Uninsulated aluminium foil flex is the everyday choice: light, easy to cut to length, and ideal for short connections between rigid duct, fans, grille boxes and valves within a heated space.

Insulated aluminium foil flex earns its premium wherever warm, moist air passes through cold spaces — bathroom and kitchen extract through lofts being the classic case. The insulation keeps the air in the duct above dew point, preventing condensation forming inside the duct and dripping back, and reduces heat loss on warm supply runs.

Both versions come in the same 16 diameters — 80, 100, 125, 150, 160, 180, 200, 224, 250, 280, 300, 315, 355, 400, 450 and 500mm — matching spiral duct, fan spigots and grille box connections directly, and each 10m length cuts to size on site so one box covers many connections.

Fitting foil flex well

Pull each section reasonably taut, avoid tight kinks, and support longer spans so the duct cannot sag — a rippled, slack run costs real airflow. Push the duct fully over its spigot and secure with a hose clip for an airtight fit; on insulated flex, dress the insulation over the joint afterwards so the vapour layer stays continuous. Stocked sizes ordered by 3pm are despatched for next-day delivery, with free UK mainland delivery on orders over £400 ex VAT.