Aluminum
Aluminum is a lightweight, silvery-white metal known for its excellent corrosion resistance, high strength-to-weight ratio, and versatility in construction applications ranging from window frames to structural components.
Composition
Primarily pure aluminum (Al) with small amounts of alloying elements such as copper, manganese, magnesium, silicon, and zinc depending on the specific alloy series. Common construction alloys include 6061 (structural applications), 6063 (extrusions), and 3003/3004 (sheet applications).
Properties
Density
168 lbs/ft³ (2,700 kg/m³)
Approximately one-third the weight of steel, making it ideal for lightweight applications.
Tensile Strength
10,000-60,000 psi (70-414 MPa)
Varies significantly based on alloy and temper, with higher-strength alloys used for structural applications.
Thermal Conductivity
136 BTU/hr·ft·°F (235 W/m·K)
Excellent thermal conductor, approximately 4 times more conductive than steel.
Electrical Conductivity
61% IACS
Good electrical conductor (61% of the International Annealed Copper Standard).
Corrosion Resistance
Excellent
Forms a natural protective oxide layer that prevents further oxidation, particularly effective in neutral pH environments.
Thermal Expansion
13.1 × 10⁻⁶ in/in/°F
Approximately twice that of steel, requiring careful consideration in design and installation.
Applications
Window and Door Frames
Widely used for framing systems due to lightweight properties, corrosion resistance, and ease of extrusion into complex profiles. Thermal breaks are often incorporated to improve energy performance.
Curtain Wall Systems
Forms the structural framework for glass and panel infills in modern building facades, offering lightweight support and design flexibility while accommodating thermal movement.
Roofing and Cladding
Used as standing seam roofing, shingles, and wall panels, providing lightweight, durable, and low-maintenance building envelopes with excellent weather resistance.
Structural Components
Employed in space frames, trusses, and structural members where weight reduction is critical, such as long-span roofs, canopies, and transportation structures.
Railings and Balustrades
Popular for handrails, guardrails, and decorative elements due to corrosion resistance, light weight, and ability to be finished in various ways including anodizing and powder coating.
HVAC Systems
Extensively used in ductwork, diffusers, and equipment housings due to its lightweight nature, corrosion resistance, and excellent thermal conductivity.
Advantages
- Exceptional strength-to-weight ratio, approximately one-third the density of steel
- Excellent corrosion resistance due to natural oxide layer formation
- Highly recyclable with minimal quality loss through repeated recycling
- Non-combustible and non-toxic, suitable for various building applications
- Versatile in forming, joining, and finishing methods
- Low maintenance requirements and long service life
- Available in various finishes and colors through anodizing and coating
- Good reflectivity of light and heat, contributing to energy efficiency
Limitations
- Lower strength compared to steel, requiring larger sections for equivalent structural capacity
- Higher thermal expansion requiring careful detailing for movement
- Susceptible to galvanic corrosion when in contact with certain metals
- Higher initial cost compared to some alternative materials
- Requires special welding techniques and skilled labor
- High embodied energy in primary production (though offset by recyclability)
- Thermal conductivity can create challenges for thermal performance without breaks
- Softer than steel and more susceptible to denting and scratching
Sustainability Profile
Aluminum has a mixed sustainability profile with excellent end-of-life characteristics but high initial production impacts. Primary aluminum production is energy-intensive, requiring approximately 15 kWh of electricity per kilogram produced, primarily from the electrolysis process. However, recycled aluminum requires only about 5% of the energy needed for primary production, with minimal quality degradation through multiple recycling cycles. The current global recycling rate for aluminum in the building sector exceeds 85% in many developed countries. Aluminum's durability and corrosion resistance contribute to long service life (50+ years for many building applications), reducing life-cycle impacts. Modern extrusion and manufacturing processes have significantly reduced waste, and aluminum's lightweight nature can reduce transportation energy and structural support requirements in buildings.