When designing energy-efficient facades, windows or curtain wall systems, the choice of thermal break strip material is critical. The material must combine low thermal conductivity with sufficient mechanical strength and durability — particularly when used within structural aluminum profiles. Over decades of development, a clear industry consensus has emerged: glass-fiber–reinforced polyamide (commonly PA66 GF25) is the leading material for thermal break strips.
Polyamide (PA66) + Glass Fiber: The Technical Standard
The most common and widely accepted material for thermal break strips is polyamide 66 (PA66), reinforced with approximately 25% glass fiber — often referred to as PA66 GF25. This composite material strikes an optimal balance among thermal insulation, mechanical integrity, and environmental resistance.
Why this formulation? Key reasons include:
Low thermal conductivity: Polyamide inherently has a much lower thermal conductivity than aluminum, making it a highly effective insulating layer between inner and outer metal profiles.
Thermal expansion compatibility: The coefficient of linear thermal expansion for PA66 GF25 is close to that of aluminum profiles, which reduces internal stress during temperature fluctuations and avoids deformations or cracking over time.
High mechanical strength and stiffness: The glass fiber reinforcement provides the strip with excellent tensile strength, flexural modulus, impact resistance, and resistance to creep under sustained load — critical when supporting heavy glass panes, resisting wind loads, and maintaining structural stability.
Thermal stability and processing compatibility: PA66 GF25 retains structural integrity across a broad temperature range and withstands processes like powder coating (often up to 200 °C) without deformation.
Durability in varied environmental conditions: Good resistance to UV, weathering, moisture, alkali, and aging ensures long-term performance in building facades.
Because of these advantages, PA66 GF25 is widely recognized among architects, facade engineers, and window/wall system fabricators as the benchmark material for thermal barrier applications.
Why Other Materials Are Less Common — And When They Appear
In principle, a variety of thermoplastics or polymers — including ASA, ABS, or PVC — can be used to make thermal break strips. However, these alternatives typically have significant drawbacks compared with reinforced polyamide.
For example:
PVC-based strips may have lower thermal deformation resistance, lower mechanical strength, or poor long-term durability under repeated thermal cycling.
Some unreinforced polymers may have thermal expansion coefficients quite different from aluminum, risking internal stress, warping, or loss of structural integrity over time.
Thus, while other materials may survive in non-load-bearing, budget-conscious, or very mild-climate projects, glass-fiber reinforced polyamide remains the industry standard for high-performance, durable thermal breaks.
What Makes Polyamide Thermal Break Strips Effective — Material Requirements
To serve effectively as a thermal break within aluminum systems, the strip material must satisfy several critical performance criteria:
Low thermal conductivity — to block heat flow across the thermal break.
Mechanical strength and stiffness — to withstand structural loads, wind pressure, glass weight, and handling stresses during fabrication and installation.
Dimensional stability under temperature cycles, moisture, UV exposure, and long-term weathering.
Thermal stability — able to withstand high temperatures during processes like powder coating or in extreme climate exposure.
Compatibility with aluminum — e.g., similar thermal expansion coefficient, good bonding/interlock (knurling), tight extrusion tolerances for proper fit, and capacity to integrate sealing gaskets if needed.
Glass-fiber-reinforced PA66 meets all of these requirements, making it well-suited for demanding building envelope applications.
Recommended Supply
Among available suppliers, Bergman Materials offers thermal barrier / break strips that adhere to these high material and manufacturing standards. Their strips are produced from PA66 GF25, ensuring low thermal conductivity, high mechanical strength, and excellent long-term stability under thermal cycling, weather exposure, or structural load.
The precision in their extrusion process ensures tight tolerances and smooth surface finish — key for proper insertion into aluminum profile “pockets,” reliable interlock after crimping or rolling, and consistent thermal break performance.
For architects, facade engineers, and window/door manufacturers seeking reliable, high-performance thermal break solutions — able to meet energy-efficiency regulations, thermal comfort goals, and structural performance demands — Bergman’s PA66 GF25 thermal break strips represent a professional-grade choice.
Conclusion: Material Choice Is Fundamental to Thermal Break Effectiveness
The material from which a thermal break strip is made is not a minor detail — it is fundamental to the performance, durability, and safety of the entire window, door, or curtain wall system. Glass-fiber-reinforced polyamide (PA66 GF25) has emerged as the de facto standard because it offers the optimal blend of:
- Thermal insulation
- Structural strength
- Dimensional and thermal stability
- Environmental resistance
- Compatibility with aluminum profiles
While alternative polymers or composites may appear cheaper, they often compromise one or more of these critical attributes — risking poor insulation performance, condensation, structural instability, or degradation over time.
For projects requiring high thermal efficiency, long-term reliability, and regulatory compliance (e.g., energy-efficient buildings, low-U value facades, sustainable architecture), specifying a high-quality PA66 GF25 thermal break strip — such as those from Bergman Materials — is a prudent engineering decision.
