The ductwork that carries the air between the fan, the rooms and the outside is built from flexible ducting, insulated ducting and spiral duct, in sizes from Ø100 to Ø630. The fittings, dampers and rain hoods for the same diameters are on this page too.
KROS 100 round regulating damper for precise airflow control in ventilation systems. Galvanized steel, rubber gasket, manual adjustment. Suitable for 100mm round ducts.
DEC International GREENDEC Ø100mm flexible insulated antibacterial air duct (1.0m) is a hygienic, sound-attenuating HVAC duct designed for quiet and efficient air distribution with 25mm glass wool insulation that reduces noise, prevents condensation, and minimizes heat loss. Built for demanding environments such as hospitals, cleanrooms, heat recovery and air-conditioning systems, it supports airflow up to 30 m/s and pressures up to 2000 Pa.
100mm / 3m semi-flexible aluminium air duct SEMIDEC, DEC International
DEC International Semidec 100/3m a semi-flexible air duct Ø100mm made from a single layer of aluminum that is highly resistant to corrosion. The special seam construction ensures excellent air tightness and flexibility.
100mm/0.5m Greendec flexible insulated antibacterial air duct, DEC International
DEC International GREENDEC Ø100mm flexible antibacterial sound attenuating air duct (0.5m) is an insulated acoustic ventilation duct with 25mm glass wool insulation for thermal, odour and noise reduction. Featuring Sanitized® antibacterial protection, it is ideal for hospitals, clean rooms, and professional HVAC systems.
100mm/3 m extra flexible laminated air duct ProFlex 5X Black (5 layers), HavenPoint
HavenPoint ProFlex 5X Black – ultra flexible premium 100 mm x 3 m laminated flexible air duct. With 5-layer aluminium, polyester, and copolymer construction, it delivers maximum flexibility, heat and steam resistance (-30 °C to +140 °C, short-term up to +300 °C), and long-lasting durability. Compared to PVC and standard aluminium ducts, ProFlex 5X ensures higher tear resistance, less smoke in case of fire, and superior mechanical protection. Certified to DIN EN 13180, RoHS & REACH compliant. Made in EU.
100 mm x 3 m the HavenPoint ProFlex 5X Gray is a high-end laminated air duct in a gray color engineered for both residential and industrial ventilation systems. Designed with 5-layer construction – 3 aluminium layers, 1 polyester layer, and 1 outer copolymer protective layer – it ensures exceptional flexibility, mechanical strength, and long service life. Perfect for cooker hoods, bathroom ventilation, dryers, and other systems.
102, 127, 160, 203 and 254mm / 10m aluminium air duct Aludec REGA
Aludec REGA is a flexible, non-insulated air duct made of aluminium-polyester laminate. It is a the perfect ducting solution, ensuring flawless airflow and exhaust. Its superior quality and corrosion resistance guarantee reliable performance for many years. It is suitable for use in households as well as commercial or industrial facilities. Available in diameters 102mm, 127mm, 160mm, 203mm, 254mm and 315mm.
102mm x 10m flexible laminated aluminium air duct Combidec 2000 BLUE DEC International
102 mm/10 m Combidec 2000 Blue flexible laminated aluminium air duct Ø100 mm from DEC International is a heavy-duty ventilation duct offering high mechanical strength, excellent flexibility, and proven fire safety. Ideal for HVAC systems, mechanical ventilation, and industrial air handling applications.
102mm x 10m ISODEC 25 thermally insulated aluminium air duct (insulation 25mm) DEC International
The DEC International ISODEC 25 thermally insulated air duct Ø102 mm designed for air conditioning and ventilation systems, helping reduce condensation and maintain stable air temperature. It features a multi-layer structure with an inner aluminium duct, glass wool insulation, and an outer aluminium jacket, providing durability and thermal protection. Suitable for various HVAC applications, it operates in a temperature range from -30°C to +140°C and with air velocity up to 30 m/s for reliable airflow.
102mm x 10m SONODEC 25 acoustic insulated aluminium air duct (insulation 25mm) DEC International
The DEC International SONODEC 25 Ø102 mm a thermally and acoustically insulated flexible aluminium air duct designed for air conditioning and air supply systems where noise reduction and condensation prevention are required. It features a perforated aluminium inner duct, 25 mm glass wool insulation, anti-migration barrier, and aluminium laminate outer jacket, helping reduce airflow noise and maintain stable air temperature. The duct has a 102 mm diameter, 10 m length, supports air velocity up to 30 m/s, and operates in a temperature range from -30°C to +140°C.
KROS 125 is a high-quality round regulating damper with rubber gasket for efficient airflow control. Constructed from corrosion-resistant galvanized steel, suitable for 125mm round ducts.
125 mm round shut-off and regulating damper with sealing gasket and motor / handle platform KRTS-4
KRTS-4 125 round shut-off and regulating damper with sealing gasket – galvanized steel, airtight, and durable solution for precise airflow control in HVAC duct systems.
125mm / 3m semi-flexible aluminium air duct SEMIDEC, DEC International
DEC International SEMIDEC Ø125mm / 3m high-quality semi-flexible air duct with a single layer of corrugated aluminium. Designed for professional ventilation and air handling applications, provides excellent air tightness and mechanical strength. Heat resistant, durable and easy to install.
127mm x 10m flexible laminated aluminium air duct Combidec 2000 BLUE DEC International
DEC International Combidec 2000 Blue flexible air duct Ø127 mm (10 m) is a heavy-duty laminated aluminium ventilation duct designed for high mechanical strength, flexibility, and fire safety. Ideal for HVAC systems, mechanical ventilation, and industrial air handling, it offers excellent temperature resistance and long service life.
127mm x 10m ISODEC 25 thermally insulated aluminium air duct (insulation 25mm) DEC International
The DEC International ISODEC 25 insulated air duct Ø127 mm is a flexible insulated ventilation duct designed for HVAC and air conditioning systems, helping reduce energy loss and prevent condensation. Its multi-layer construction with an inner aluminium duct, glass wool insulation, and outer aluminium jacket improves thermal performance and durability. Suitable for a wide range of ventilation applications, it operates in a temperature range from -30°C to +140°C and supports air velocity up to 30 m/s for efficient airflow. Length 10m.
127mm x 10m SONODEC 25 acoustic insulated aluminium air duct (insulation 25mm) DEC International
The DEC International SONODEC 25 insulated air duct Ø127 mm is a fully flexible aluminium ventilation duct with thermal and acoustic insulation, designed for air conditioning and air supply systems where noise reduction and condensation control are important. It features a perforated aluminium inner duct, 25 mm glass wool insulation, an anti-migration barrier, and an aluminium laminate outer jacket, ensuring effective sound attenuation and durability. The duct supports air velocity up to 30 m/s, and operates in a temperature -30°C to +140°C.
KROS 160 is a high-quality round regulating damper with rubber gasket for efficient airflow control. Constructed from corrosion-resistant galvanized steel, suitable for 160mm round ducts.
160 mm round shut-off and regulating damper with sealing gasket and motor / handle platform KRTS-4
KRTS-4 160 galvanized steel HVAC damper – precise air volume control and airtight shut-off for round duct ventilation.
160mm x 10m flexible laminated aluminium air duct Combidec 2000 BLUE DEC International
160 mm / 10 m Combidec 2000 Blue flexible laminated aluminium air duct Ø160 mm from DEC International is a heavy-duty ventilation duct offering high mechanical strength, excellent flexibility, and proven fire safety. Ideal for HVAC systems, mechanical ventilation, and industrial air handling applications.
160mm x 10m ISODEC 25 thermally insulated aluminium air duct (insulation 25mm) DEC International
The DEC International ISODEC 25 insulated air duct Ø160 mm is a reliable solution for air distribution in HVAC systems, helping maintain consistent air temperature during operation. Its triple-layer construction with an inner aluminium duct, glass wool insulation, and outer aluminium jacket protects against condensation while reducing heat and cold transfer. Designed for demanding applications, it operates within a temperature range of -30°C to +140°C and supports air velocity up to 30 m/s, ensuring efficient and stable airflow. Length 10m.
160mm x 10m SONODEC 25 acoustic insulated aluminium air duct (insulation 25mm) DEC International
The DEC International SONODEC 25 insulated air duct Ø160 mm is a flexible acoustic and thermal ventilation air duct designed to improve comfort in HVAC and air supply systems. Its construction includes a perforated aluminium inner duct, 25 mm glass wool insulation, an anti-migration barrier, and a durable aluminium laminate outer jacket, which helps absorb airflow noise while limiting condensation and temperature loss. Air velocity up to 30 m/s and operates in a temperature range from -30°C to +140°C, making it suitable for a wide range of ventilation applications.
KROS 200 round regulating damper for precise airflow control in ventilation systems. Galvanized steel, rubber gasket, manual adjustment. Suitable for 200mm round ducts.
200 mm round shut-off and regulating damper with sealing gasket and motor / handle platform KRTS-4
KRTS-4 200 round shut-off and regulating damper – airtight, durable, and efficient airflow control for commercial and residential HVAC systems.
203mm x 10m flexible laminated aluminium air duct Combidec 2000 BLUE, DEC International
DEC Combidec 2000 BLUE flexible aluminium air duct Ø203mm (10m) is a high-strength laminated ventilation duct designed for mechanical aeration and steam return systems. With superior tear and puncture resistance, it withstands temperatures from -30°C to +140°C and pressures up to 3000 Pa, making it ideal for demanding HVAC applications.
Which duct where?
A single duct run often mixes more than one kind of duct. Which kind goes where depends on the part of the run.
| Part of the run | The duct | Why |
|---|---|---|
| Long straight run | Spiral duct | It is rigid and holds its shape |
| Short connection and bends | Flexible ducting | It bends to follow the route |
| Bend that must keep its shape | Semi-flexible ducting | It bends by hand and stays as it is set |
| Run through a cold space, such as a loft | Insulated ducting, thermal version | It limits heat loss and condensation |
| Run next to a bedroom or a living room | Insulated ducting, acoustic version | It absorbs fan noise inside the duct |
Flexible ducting
It bends to follow the route and joins parts that do not line up. The range has laminated aluminium and polyester duct on 10 m reels, Ø102 to Ø254, plus a five-layer duct in Ø100 on 3 m reels, in grey and black. The laminated reels are rated to 3000 Pa and 30 m/s and work from −30 to +140 °C.
Insulated and acoustic ducting
A 25 mm layer of glass wool around flexible aluminium duct limits heat loss and condensation on the duct. It comes on 10 m reels from Ø102 to Ø315. The thermal version is rated to 3000 Pa, while the acoustic version, which absorbs fan noise inside the duct, is rated to 2500 Pa. There are also short insulated lengths of 0.5 m and 1 m, Ø100 to Ø315, which are sound-attenuating and antibacterial.
Semi-flexible ducting
This aluminium duct bends by hand and holds whatever shape it is given. It comes in 3 m lengths, Ø100 and Ø125, and is rated to 3000 Pa, from −30 to +250 °C.
Spiral duct
For the rigid parts of the run there is round galvanised steel ductwork in 3 m lengths, Ø100 to Ø630, with a wall of 0.5 to 0.7 mm. It is rated to 2500 Pa and 20 m/s, from −30 to +120 °C.
Take-offs and end caps
A take-off connects a round duct to another part of the system, and an end cap closes the open end of a duct. The take-offs are straight, with a duct flange. Both parts seal with rubber for an airtight joint and come in nine diameters from Ø100 to Ø630.
Regulating dampers
A regulating damper sets the airflow in a branch; a shut-off damper closes it. There are round mechanical regulating dampers from Ø100 to Ø500, and shut-off and regulating dampers with a sealing gasket from Ø125 to Ø630. The shut-off dampers have a platform for a motor or a handle, and the handle is sold separately.
Rain hoods
A rain hood fits on the open end of a round duct and keeps water, leaves and insects out. The hoods are galvanised steel with a rubber seal, Ø100 to Ø315.
To insulate a finished run, see duct insulation.
Common questions
Is flexible ductwork any good?
Yes, for the job it is made for: short connections and bends. Pull it out to its full length, because a slack duct has folds that hold back the air. A long run is better in rigid spiral duct.
How far can you run a flex duct?
Keep a flexible run as short as the route allows. Every metre and every bend costs airflow. The fan data shows how much airflow is left at a given resistance.
What does a regulating damper do?
It sets how much air passes along a branch. With a damper in each branch, the room nearest the fan does not take all the air. A shut-off damper closes the branch fully.
What is a take-off?
A take-off is a short collar with a flange. It connects a round duct to another part of the system, and the rubber seal makes the joint airtight.
