Thermal Bridging in Aluminium Curtain Walls: Causes and Solutions

Thermal bridging represents one of the most persistent challenges in high-performance facade design. Understanding its mechanisms and mitigation strategies is essential for delivering energy-efficient building envelopes.

What Is Thermal Bridging?

A thermal bridge occurs when a material with high thermal conductivity creates a path for heat transfer across an otherwise insulated assembly. In aluminium curtain walls, the metal framing itself becomes the bridge.

Aluminium conducts heat roughly 1,000 times more effectively than the insulation materials used in facade assemblies. Even a small aluminium section can undermine the thermal performance of an entire panel.

Why It Matters

Thermal bridges increase heating and cooling energy consumption, reduce occupant comfort near facade surfaces, and can cause condensation on interior surfaces when warm humid air contacts cold framing.

In cold climates, condensation leads to mould growth, material degradation, and indoor air quality problems. In hot climates, thermal bridges increase cooling loads and can cause uncomfortable radiant heat near windows.

Thermal Breaks

The primary solution is the thermal break — a low-conductivity material inserted between the interior and exterior aluminium sections. Polyamide strips reinforced with glass fibre are the industry standard.

The effectiveness depends on the thermal break depth and geometry. Deeper breaks provide better performance but require thicker framing profiles, which affects both cost and appearance.

Structural Considerations

Thermal breaks must transfer structural loads between the interior and exterior framing sections. The polyamide material must be strong enough to handle wind loads, dead loads, and thermal movement without failure.

This creates an engineering trade-off — better thermal performance often means reduced structural capacity, requiring larger profiles or additional reinforcement.

Measurement and Standards

Thermal performance is quantified using U-values (thermal transmittance) measured in W/m²K. Lower values indicate better insulation. Modern building codes in many regions require curtain wall U-values below 2.0 W/m²K.

Thermal simulation software allows engineers to model heat flow through complex framing geometries and predict performance before manufacturing.

Practical Design Guidelines

Minimise metal-to-metal contact across the thermal barrier. Use thermally broken pressure plates and gaskets. Insulate spandrel panels continuously. Pay special attention to corners, edges, and connections where thermal bridges concentrate.

Conclusion

Managing thermal bridging requires careful attention to detail throughout the design and installation process. Small oversights can significantly degrade the performance of an otherwise well-designed facade.