Combi Ducting

12 products

Combi ducting is two-ply flexible duct with an aluminium inner and a tough PVC outer, so it stands up to knocks and abrasion better than plain aluminium flex. It suits low and medium pressure supply and extract runs in plant rooms, workshops, lofts and service voids where the duct may get scuffed. We stock Systemair combi flexible ducting from 102mm to 406mm diameter, in 6m lengths. Use the size buttons below to filter, or for trade and bulk pricing, email hello@efans.co.uk or call 0161 399 3825.

Frequently asked questions

What is combi ducting?

Flexible ductwork made from two layers: an aluminium inner duct with a PVC outer jacket. The name comes from combining the two materials. The aluminium bore gives a fire resistant inner surface and the PVC outer gives extra durability and abrasion resistance. It is also called combi flex or PVC and aluminium flexible ducting.

What is combi ducting used for?

General supply and extract runs where the duct needs to be more robust than plain aluminium flex: plant rooms, workshops, loft and ceiling voids, and exposed or demanding runs where the duct may be knocked during or after installation.

Combi, aluminium or insulated ducting?

Aluminium flexible ducting is the lightest and lowest cost option and suits warm air and short connections. Combi adds a PVC outer for durability. Insulated ducting wraps an aluminium core in glass wool insulation and is the one to use where the duct passes through a cold loft, to stop condensation and cut noise.

What sizes of combi ducting do you stock?

102mm, 127mm, 152mm, 160mm, 180mm, 203mm, 229mm, 254mm, 305mm, 315mm, 356mm and 406mm, all in 6m lengths. The imperial sizes fit the nearest metric spigot, so 102mm fits 100mm, 127mm fits 125mm and 152mm fits 150mm. Use the size buttons above the products to filter.

How do I install and join combi ducting?

Extend the duct to length, push it over the spigot and secure it with a hose clip, then seal the joint with foil tape. Pull it taut and support long horizontal runs. Cut it to length on site with a sharp knife and snips for the wire.

Can combi ducting be used outside?

It is not designed as a weatherproof external duct. Change to a rigid duct before the outside wall and finish with a weather louvre, wall outlet or roof cowl.

Does combi ducting restrict airflow?

Like any flexible duct it has more resistance than rigid duct of the same size, and more again if it is slack or kinked. Keep runs short, straight and fully extended, and use rigid duct for the main run where you can.