Sheet metal fabrication for HVAC systems is one of the highest-volume applications of fabricated sheet metal globally. Commercial buildings, data centres, hospitals and clean rooms all require custom HVAC sheet metal fabrication, rectangular ductwork, spiral round, flat oval, plenums, dampers and fittings fabricated primarily from galvanised steel, aluminium and stainless steel.
This guide gives HVAC contractors, MEP engineers and facilities procurement managers the full specification, SMACNA gauge, material and cost data for sheet metal fabrication HVAC projects, plus a clear analysis of offshore sourcing economics from India.
Manufyn fabricates HVAC sheet metal ductwork to SMACNA standards — galvanised steel, aluminium, stainless steel. Send your schedule of quantities for a 24-hour quote.
What Sheet Metal is Used in HVAC Fabrication?
HVAC sheet metal fabrication primarily uses G90 galvanised steel (275 g/m² zinc coating) for standard commercial ductwork. Aluminium 5052-H32 is specified for lightweight, architectural or high-humidity applications. Stainless steel 304 or 316 is mandatory for kitchen exhaust, pharmaceutical clean rooms, and applications involving grease-laden or corrosive air streams. Material gauge is selected per SMACNA standards based on duct dimensions and pressure class. For full material property data, see our
sheet metal materials guide.
HVAC Ductwork Types and Sheet Metal Fabrication Requirements
| Duct Type | Material | Gauge (SMACNA Class I) | Applications |
|---|---|---|---|
| Rectangular duct | Galvanised G90 | 0.50–1.20mm (GA 26–18) | Standard HVAC supply and return |
| Round duct (spiral) | Galvanised G90 | 0.50–1.00mm | Low-pressure distribution, circular sections |
| Flat oval duct | Galvanised G90 | 0.50–0.80mm | Space-constrained ceiling voids |
| Kitchen exhaust | Stainless 304/316 | 1.20–1.50mm | Grease-laden air; fire-rated |
| Pharma / clean room | Stainless 316 | 1.50–2.00mm | Sterile air systems |
| Architectural exposed | Aluminium 5052 | 1.00–1.50mm | Visible ductwork, open-plan buildings |
| Marine HVAC | Aluminium / SS316 | 1.00–2.00mm | Offshore platforms, coastal facilities |
| Industrial extract | Mild steel + epoxy | 1.50–3.00mm | Heavy industrial abrasive air streams |
SMACNA Gauge Table for Sheet Metal Fabrication HVAC Ductwork
Sheet metal fabrication HVAC gauge is governed by SMACNA (Sheet Metal and Air Conditioning Contractors’ National Association). Manufyn fabricates to SMACNA standards by default on all HVAC orders:
| Duct Width (max dimension) | SMACNA Class I (≤500 Pa) | SMACNA Class II (≤750 Pa) | SMACNA Class III (≤1,000 Pa) |
|---|---|---|---|
| Up to 300mm | 0.50mm (GA 26) | 0.50mm (GA 26) | 0.60mm (GA 25) |
| 301–450mm | 0.50mm (GA 26) | 0.60mm (GA 25) | 0.70mm (GA 24) |
| 451–600mm | 0.60mm (GA 25) | 0.70mm (GA 24) | 0.80mm (GA 23) |
| 601–750mm | 0.70mm (GA 24) | 0.80mm (GA 23) | 0.90mm (GA 22) |
| 751–900mm | 0.80mm (GA 23) | 0.90mm (GA 22) | 1.00mm (GA 20) |
| 901–1200mm | 0.90mm (GA 22) | 1.00mm (GA 20) | 1.20mm (GA 18) |
| >1200mm | 1.00mm (GA 20) | 1.20mm (GA 18) | 1.50mm (GA 16) |
Aluminium gauge: one step heavier than galvanised steel equivalent (lower stiffness). Stainless: equivalent to galvanised steel. Verify against the SMACNA edition referenced in your project specification.
HVAC Sheet Metal Fittings — What Manufyn Supplies
A complete HVAC sheet metal fabrication package includes all fittings, not just straight duct runs:
- Elbows: mitered (multi-piece) or radius; turning vanes for low-loss rectangular bends
- Tees and junctions: branch takeoffs, shoe tees, conical tees for round systems
- Reducers and transitions: concentric and eccentric, rectangular or round
- Plenums: supply and return air plenums for AHU connections
- Access doors: inspection openings per SMACNA — hinged or slide-in
- Volume control dampers: single-blade, multi-blade, opposed-blade VAV
- Flexible connections: vibration isolation at AHU — canvas or glass fibre
How to Specify Sheet Metal Fabrication HVAC for an Overseas Fabricator
- Schedule of quantities: all duct sections with dimensions (W×H or diameter), length, gauge and material
- Project specification: extract the relevant SMACNA table and pressure class for your project
- Drawing package: plan and elevation showing duct routing — DXF or PDF
- Fittings list: quantities and dimensions of all elbows, tees, reducers, access doors
- Finish specification: standard G90 galvanised, or specific coating requirement
- Delivery address and date: allows Manufyn to plan freight and confirm lead time
Offshore vs Domestic Sheet Metal Fabrication HVAC: Economics
| Factor | UK/AU/US Domestic | Manufyn India |
|---|---|---|
| Labour rate | $35–55/hr | $4–8/hr |
| Fabrication cost index | 1.0× (baseline) | 0.35–0.45× |
| Sea freight to UK | — | 25–30 days; ~$150–200/CBM |
| Sea freight to AU | — | 18–22 days; ~$180–240/CBM |
| Sea freight to US East | — | 28–35 days; ~$160–200/CBM |
| Total landed saving | — | 30–50% on total HVAC ductwork cost |
| SMACNA compliance | Standard | Standard — Manufyn fabricates to SMACNA by default |
Country-specific HVAC sheet metal fabrication savings: UK · US · Australia · UAE
Send your HVAC sheet metal fabrication schedule of quantities to Manufyn’s team — SMACNA-compliant, G90/aluminium/stainless, 24-hour quote. See also our sheet metal assembly service
Frequently Asked Questions — Sheet Metal Fabrication HVAC
HVAC sheet metal fabrication primarily uses G90 galvanised steel (275 g/m² zinc) for standard commercial ductwork, aluminium 5052-H32 for lightweight or architectural applications, and stainless steel 304 or 316 for kitchen exhaust, pharmaceutical and marine systems. Gauge is selected per SMACNA standards. Full material data: sheet metal materials guide
HVAC ductwork gauge ranges from 0.50mm (GA 26) for small duct at Class I pressure to 1.50mm (GA 16) for large duct at Class III. The SMACNA gauge table above specifies minimum gauge by duct width and pressure class. Manufyn fabricates to the SMACNA gauge table by default on all sheet metal fabrication HVAC orders.
Yes — Manufyn fabricates HVAC sheet metal fabrication to SMACNA standards and ships globally. Sea freight: UK 25–30 days; Australia 18–22 days; US East Coast 28–35 days. Pre-planned ductwork is typically 30–50% cheaper landed from India vs domestic fabrication.
Manufyn’s HVAC sheet metal fabrication service includes kitchen exhaust ductwork in SS 304 and 316 to SMACNA Kitchen Ventilation Standards. Minimum gauge 1.2mm SS. Contact info@manufyn.com with your schedule of quantities.
Need Sheet Metal Parts Fabricated?
Manufyn — ISO 9001 Certified Sheet Metal Fabrication from India
Serving US, UK, Australia, UAE, Canada, Germany and 30+ countries
Quote in 24 hrs · No Minimum Order · Free DFM Review · NDA on Request
WhatsApp: +91 84840 32262 | Email: info@manufyn.com
ISO 9001 · 24-Hr Quote · No MOQ · 5-Day Prototypes · Free DFM · 30+ Countries
