A double-layer galvanised spiral duct with a 15 mm insulation layer between the inner and outer skins. The double-wall construction gives the round duct a clean factory-finished insulated appearance while improving both thermal and acoustic performance. The inner and outer layers are 275 galvanised steel sheet with insulation foam between them.
In ceiling voids, service risers, floor build-ups and wall chases, ducting is rarely the whole system — it is one link in a chain. Getting it wrong shows up later as condensation, pressure loss, noise transmission and awkward routing. The selection criteria that actually drive performance are air-tightness, pressure drop and acoustic performance, and those are the three things a buyer should confirm before placing an order.
Pressure loss in a duct run does not scale linearly with diameter — it scales roughly with the inverse fifth power of it. That single relationship explains why stepping a run down by one nominal size to save ceiling depth so often destroys the performance of the whole system. A modest reduction in diameter can multiply the resistance of that section several times over, and the fan then has to run faster to compensate, which raises both energy consumption and noise. When a void is tight, the correct answer is almost always to re-route rather than to reduce the diameter.
Warm moist air passing through a duct that is colder than its dew point will deposit water somewhere along the run. In practice the deposit forms at the coldest point, which is normally a joint, a bracket or a section that passes through an unconditioned loft or a wall chase. The damage is progressive and largely invisible: staining appears on a ceiling months after the actual defect occurred, by which time the insulation and often the substrate behind it are already affected. Continuous, unbroken insulation across every joint is the only reliable defence, and it costs nothing at installation time.
Every 275 Galvanized Spiral Duct With 15mm Insulation Layer, Inner‑outer Double‑layer Galvanized Ventilation Pipe we ship is produced on our own production line in Dezhou, Shandong, China. Because we control the tooling and the forming equipment directly, we can guarantee that the product you receive in container three is dimensionally identical to the sample you approved in the first order. That consistency is difficult to achieve when production is outsourced, and it is the single most common complaint we hear from buyers who have tried sourcing this category through intermediaries.
Our mould shop supports custom development for 275 Galvanized Spiral Duct With 15mm Insulation Layer, Inner‑outer Double‑layer Galvanized Ventilation Pipe. If your project needs a non-standard size, a specific wall thickness, a particular colour or a branded face plate, we can build the tooling and run a trial batch for approval before committing to a full production run. Typical custom development takes two to four weeks from drawing approval to first article, depending on the complexity of the part.
Confirm the exact size or model you need against the specification table below. Where a project mixes sizes on one run, check that every transition is made with a matching reducer rather than by forcing parts together — the latter is the single most common cause of leakage and pressure loss on site.
The material and layer build-up determine how the product behaves over a 15–25 year service life. Read the construction column carefully: two products that look identical on a photograph can differ entirely in wall thickness, insulation layer and fire performance.
| Item | Specification |
|---|---|
| Description | Multiple diameters available; customized length; insulation thickness:15mm |
| Material / Construction | Inner & outer layer: 275 galvanized steel sheet; Middle layer: thermal insulation foam |
Matches our galvanised stamped elbow segments and insulated galvanised spiral duct. For larger systems see the duct silencer.
GUANDE manufactures 275 Galvanized Spiral Duct With 15mm Insulation Layer, Inner‑outer Double‑layer Galvanized Ventilation Pipe at our factory in Dezhou, Shandong, China, and ships direct to HVAC contractors, distributors and project specifiers worldwide. Wholesale, OEM and ODM programmes are welcome. Because we manufacture this product in our own plant, we control the tooling, wall thickness, material grade and quality inspection at every stage — not just the final packing. That means we can produce non-standard sizes, custom colours and private-label versions against your drawings, and we can adjust a production run when a project specification changes. Tell us your target market and we will confirm packaging, labelling and documentation to suit it.
The products below are routinely specified alongside the item discussed in this guide. GUANDE manufactures the full range in our own plant for consolidated shipping:
Q: How thick is the insulation?
A: 15 mm, as listed in the specification table below.
Q: Are elbow segments available?
A: Yes, see our matching galvanised stamped elbow segments.
Q: Can lengths be customised?
A: Yes, duct lengths can be made to suit the project.
The southeast corner of the private entrepreneurship park in Huadian Town, Qihui County, Dezhou City, Shandong Province