The material you choose for ductwork affects cost, weight, longevity, and code compliance. Most installers default to galvanized steel—and for good reason. But there are situations where aluminum or stainless steel is the better call. Here's how to decide.
| Property | Galvanized Steel | Aluminum | Stainless Steel |
|---|---|---|---|
| Relative Cost | 1x (baseline) | 1.7x | 3.4x |
| Weight | Baseline | 65% lighter | Similar to galv |
| Corrosion Resistance | Good (zinc coating) | Excellent (natural oxide) | Superior (chromium oxide) |
| Max Temp | 400°F | 350°F | 1500°F+ |
| Weldability | Easy (MIG/spot) | Moderate (TIG) | Moderate (TIG) |
| Available Gauges | 26, 24, 22, 20 | 26, 24, 22, 20 | 26, 24, 22, 20 |
Galvanized steel accounts for roughly 95% of all HVAC ductwork installed in the United States. The zinc coating provides reliable corrosion protection for 20-30 years in typical indoor environments. It's the most affordable option, it's easy to work with in the field, and every sheet metal worker is trained on it.
Best for: Residential heating and cooling, commercial HVAC, industrial ventilation, general supply and return air.
Avoid when: Weight is critical, the environment is highly corrosive (salt air, chemical exposure), or temperatures exceed 400°F.
At 65% lighter than galvanized steel, aluminum is the go-to material when installation weight is a constraint. A 24”×24”×60” straight duct section in 24-gauge aluminum weighs about 8 pounds versus 23 pounds in galvanized. That difference is significant when you're working on rooftops, hanging duct from bar joists, or shipping large quantities.
Aluminum also has excellent natural corrosion resistance—it forms a protective oxide layer that doesn't require a coating. This makes it suitable for coastal environments where salt air would attack the zinc coating on galvanized steel.
Best for: Rooftop installations, suspended duct in high ceilings, marine/coastal environments, weight-sensitive structures, exposed architectural ductwork.
Avoid when: Budget is tight (1.7x cost premium), temperatures exceed 350°F, or the duct will be welded extensively in the field (aluminum TIG welding requires more skill than steel MIG).
Stainless steel is the premium option at roughly 3.4x the cost of galvanized. You specify it when the application demands it:
Best for: Any application involving high heat, corrosive chemicals, sanitation requirements, or code mandates for non-combustible materials.
Avoid when: Standard HVAC applications where galvanized would perform identically at a third of the cost.
Regardless of material, gauge selection follows system pressure class:
Ask three questions:
If none of those apply, galvanized steel is the right answer. It's proven, affordable, and universally available.
All three materials. Any size. Instant pricing.
Switch materials in the designer to compare costs side by side