When planning a rooftop HVAC installation, the focus tends to be on the unit itself—its tonnage, efficiency, and brand. But beneath every reliable rooftop unit is an equally important structure: the HVAC curb. And when it comes to choosing the right curb, one of the most common questions contractors and project managers ask is: Should I go with steel or aluminum?

Both materials have their strengths, and the right choice often comes down to the specific needs of your project. Let’s break down the pros, cons, and ideal applications of steel vs. aluminum HVAC curbs so you can make an informed decision that aligns with your goals, budget, and building environment.

1. Strength & Structural Integrity

Steel Curbs:
Steel is known for its exceptional strength and load-bearing capacity. It’s the industry standard for projects where durability is non-negotiable—especially on large commercial buildings with heavy rooftop units, variable weather conditions, or seismic requirements.

• Excellent for supporting high-capacity RTUs

• Resists denting, bending, or warping under heavy loads

• Ideal for areas with high wind uplift or snow loads

Aluminum Curbs:
Aluminum is lighter and not as strong as steel, but still provides good structural integrity for smaller or medium-sized rooftop units. It can handle typical rooftop stresses, but may not be ideal for oversized equipment or extreme climates.

The Verdict:
If your project involves large or heavy HVAC units, or you’re working in a region with strict building codes, steel offers the rugged reliability needed.

2. Weight & Ease of Handling

Steel Curbs:
Steel is dense and heavy. While its strength is unmatched, the added weight can make handling and installation more labor-intensive. Heavier curb assemblies may require additional manpower or equipment during installation.

Aluminum Curbs:
Aluminum is significantly lighter—up to one-third the weight of steel. This makes aluminum curbs much easier to transport, position, and install, especially in rooftop projects with limited crane capacity or access constraints.

The Verdict:
If speed and ease of installation are top priorities—or if you’re working on a smaller commercial building with weight restrictions—aluminum may be the better fit.

3. Corrosion Resistance & Weather Durability

Steel Curbs:
Steel curbs typically require a protective coating (such as galvanizing or powder coating) to prevent rust and corrosion. In high-moisture or coastal environments, untreated steel can degrade over time.

Aluminum Curbs:
Aluminum is naturally corrosion-resistant. It doesn’t rust, which makes it a great choice for coastal regions, humid climates, or facilities with exposure to chemicals or moisture.

The Verdict:
For projects in salt-air, marine, or humid environments, aluminum offers superior long-term durability with minimal maintenance.

4. Cost Considerations

Steel Curbs:
Steel is generally less expensive in terms of raw materials. However, costs can increase due to its heavier weight (more expensive to ship and install) and the need for corrosion-resistant coatings.

Aluminum Curbs:
Aluminum is usually more expensive per pound, but its light weight reduces shipping costs and simplifies handling. In the long run, its resistance to corrosion can reduce maintenance and replacement costs.

The Verdict:
If initial material cost is your primary concern and the environment is not overly harsh, steel may offer better value. But if you're considering total lifecycle costs, aluminum can save you money on installation and maintenance.

5. Sustainability & Energy Efficiency

Steel Curbs:
Steel is recyclable and commonly reused in construction, but it has a higher embodied energy (energy required to produce the material) compared to aluminum.

Aluminum Curbs:
Aluminum is also fully recyclable and has a lower weight, which can slightly reduce the load on your rooftop structure and contribute to energy-efficient designs. Some projects prioritize aluminum for LEED certification or sustainability targets.

The Verdict:
Both materials are sustainable, but aluminum may edge ahead in projects with green building goals or strict energy-efficiency requirements.

Which One Is Right for You?

There’s no one-size-fits-all answer—but here’s a quick summary to guide your decision: