Route Anywhere. Connect Anything.
Spiro-Flex flexible ducting is a super lightweight, compressible air duct constructed from two layers of polyester tape — one metallised — helically wound to encase a spring steel wire. This two-layer design allows Spiro-Flex to conform to any desired duct route while maintaining its circular cross-section, making it the most versatile option in the Spiro duct range.
Used by HVAC contractors and mechanical engineers for terminal connections, VAV hookups, and retrofit projects, Spiro-Flex bridges the gap between the rigid main duct run and the final diffuser or grille. The insulated and acoustic insulated versions add thermal and sound control where required.
Why Choose Spiro-Flex Flexible Ducting?
- Compressible and bendable to fit any duct route without additional fittings
- Two-layer aluminised PET foil and spring steel wire construction
- Available in 3m and 6m standard lengths
- Plain, thermally insulated, and acoustic insulated options
- Suitable for low-pressure HVAC systems
- Complies with ISO 9705, AS 4254, AS 1530.3, and UL 181
Ideal Applications
- Terminal connections from rigid duct to diffusers and grilles
- VAV terminal and fan coil unit hookups
- Concealed ceiling spaces requiring flexible routing
- Retrofit projects where rigid duct installation is impractical
- Residential heating, cooling, and ventilation systems
- Bathroom extract and kitchen exhaust ducting in houses, apartments, and townhouses
- Heat pump and split-system air transfer connections in residential properties
- New-build and renovation residential HVAC installations where flexibility is required
- Underfloor and ceiling air distribution in domestic settings
- Noise-sensitive areas using the acoustic insulated option
Flexible vs Semi-Rigid vs Rigid Ducting
| Criteria |
Spiro-Flex |
Spiro-Set |
Spiro-Loc |
| Type |
Flexible ducting |
Semi-rigid aluminium ducting |
Rigid steel ducting |
| Airflow consistency |
Lower |
High |
Highest |
| Installation |
Compressible and flexible — no fittings required |
Hand-bendable on site |
Requires fittings and fabrication |
| Self-supporting span |
No |
Yes |
Yes – up to 3,600mm hanger spacing |
| Pressure rating |
Low pressure only |
±1.5 kPa |
Up to 2500Pa positive pressure |
| Best suited for |
Terminal connections, VAV hookups, and short duct runs |
Commercial HVAC, retrofits, exposed ceilings, and VAV connections |
Main duct runs, high-pressure systems, and long spans |
Spiro-Flex Flexible Ducting Features
Lightweight Two-Layer Construction
Spiro-Flex is constructed from two layers of polyester tape — one metallised — helically wound to encapsulate a spring steel wire. This design keeps weight to a minimum while allowing the duct to compress for easy handling and storage, and expand to full diameter on installation. The cross-section is deformable, allowing Spiro-Flex to navigate tight ceiling cavities and around obstructions without additional bends or fittings.
Insulated Options for Thermal and Acoustic Control
The insulated version (SPI-FP) is sheathed in a seamless, flame-retardant printed outer sleeve over a lofted polyester blanket, providing thermal resistance of R1.0 m²K/W. The acoustic insulated version (SAI-FP) adds sound attenuation for use in noise-sensitive areas such as offices, hotels, and healthcare facilities. Both insulated options are available in diameters from 100mm to 300mm.
Simple, Fast Installation
Spiro-Flex connects directly to rigid or semi-rigid ductwork, diffusers, and grilles using standard spin collars, spin connectors, and duct ties. Available in standard 3m and 6m lengths — the 6m option reduces joins on longer runs. Installation should be carried out in accordance with SMACNA guidelines and AS 4254.
Available Flexible Ducting Options
- Type SPU – Plain, uninsulated: two-layer aluminised PET foil and spring steel wire construction. Available in diameters 100mm to 500mm in 3m and 6m lengths.
- Type SPI-FP – Plain, insulated: SPU liner with lofted polyester blanket and seamless flame-retardant outer sleeve. Thermal resistance R1.0 m²K/W. Available in diameters 100mm to 500mm.
- Type SAI-FP – Acoustic, insulated: as SPI-FP with acoustic insulation treatment for noise attenuation. Available in diameters 100mm to 300mm.
Flexible Ducting Specifications
| Construction |
Two-layer: fibreglass reinforced aluminised PET foil tape, helically wound, encapsulating a spring steel wire |
| Standard diameters |
100, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500 mm |
| Acoustic insulated diameters |
100, 125, 150, 175, 200, 225, 250, 300 mm |
| Standard lengths |
3m and 6m; 500mm also available; other lengths to special order |
| Insulation |
Lofted polyester blanket, R1.0 m²K/W, with seamless flame-retardant polyethylene vapour barrier outer sleeve |
| Pressure rating |
Low pressure HVAC systems |
| NZBC compliance |
Meets energy efficiency requirements of H1/VM3 Clause 5.2.1 |
Testing and Compliance
- Complies with ISO 9705, AS 4254, AS 1530.3, and UL 181 where applicable
- ISO 9705 room fire test: 1-S Group Number Classification for smoke production rate, per NZBC Verification Method C/VM2 Appendix A
- AS 1530.3 plain (SPU): ignitability 0, spread of flame 0, heat evolved 0, smoke developed 1
- AS 1530.3 insulated (SPI-FP / SAI-FP): ignitability 0, spread of flame 0, heat evolved 0, smoke developed 3
- Joint sealing in accordance with SMACNA and AS 4254 requirements
