Aluminium has become one of the most widely specified materials in modern glazing. Its strength, slim sightlines, corrosion resistance, and architectural flexibility make it ideal for contemporary homes and commercial buildings alike. From large sliding doors to minimalist rooflights, aluminium frames allow designers to maximise glass while maintaining structural integrity. However, aluminium also presents a significant challenge that cannot be ignored: it is an excellent conductor of heat.
Without insulation, aluminium frames readily transfer external temperatures to the inside of a building. This leads to heat loss in winter, overheating in summer, cold internal surfaces, and a high risk of condensation. These issues are particularly noticeable in rooflights and large glazed openings, where exposure is greatest. The solution to this problem is the thermal break aluminium window, a design that fundamentally changes how aluminium performs thermally.
What Is a Thermal Break?
A thermal break is an insulating barrier built into an aluminium frame that separates the internal and external sections of the metal profile. Its purpose is to interrupt the direct path of heat flow through the frame. In effect, it “breaks” the thermal bridge that would otherwise allow heat to pass freely from one side of the frame to the other.
In a traditional, non-insulated aluminium window, the frame is formed from a continuous piece of metal. Because aluminium conducts heat so efficiently, any temperature difference between inside and outside is quickly equalised through the frame. This means internal frame surfaces become cold in winter and warm in summer, regardless of indoor conditions.
A thermal break changes this behaviour. By inserting a non-conductive material between the two halves of the frame, heat transfer is dramatically reduced. The aluminium still provides strength and durability, but the insulating material controls thermal performance. The result is the thermal break aluminium window, capable of meeting modern energy-efficiency expectations.
Why Aluminium Frames Need Insulation
Aluminium’s popularity in construction has little to do with its thermal properties. Structurally, it is excellent; thermally, it is problematic. Aluminium has a thermal conductivity of around 205 W/mK, which means it transfers heat extremely quickly compared to insulating materials such as timber or plastic.
When aluminium frames are left uninsulated, several problems arise simultaneously. Heat loss increases, which raises energy demand and heating costs. Internal surfaces become cold, reducing occupant comfort and making rooms feel draughty even when air temperatures are adequate. Moisture in the indoor air condenses on these cold surfaces, leading to visible water droplets, staining, and sometimes mould growth.
These issues are not confined to old buildings. Even new aluminium glazing can perform poorly if it lacks proper insulation. This is why thermal breaks have become essential in modern aluminium windows and rooflight design.
Understanding Thermal Bridging in Aluminium Glazing
Thermal bridging occurs when a conductive material allows heat to bypass insulation. In glazing systems, the frame is often the weakest point thermally, particularly when it is made from metal. Aluminium frames without thermal breaks form a continuous conductive bridge between the external and internal environments.
Cold bridging rooflights are a common and visible example of this problem. Rooflights are exposed to external temperatures on all sides and are positioned where warm, moist air naturally collects. An uninsulated aluminium rooflight frame becomes a cold sink in winter, drawing heat out of the building and lowering the internal surface temperature of the frame and surrounding glass.
This not only increases heat loss but also creates ideal conditions for condensation. Many complaints about dripping rooflights are not caused by leaks but by cold bridging through uninsulated frames a key issue addressed by Skylights & Roof Lanterns through properly thermally broken aluminium systems.
The Polyamide Thermal Break Explained
The most widely used solution for insulating aluminium frames is the polyamide thermal break. Polyamide is a high-performance engineering plastic, often reinforced with glass fibres, that combines low thermal conductivity with high mechanical strength.
In a thermally broken aluminium frame, the polyamide strip is mechanically bonded between the internal and external aluminium profiles. This bond is strong enough to maintain structural integrity while providing an effective thermal barrier. Because polyamide is stable across a wide range of temperatures and resistant to moisture and ultraviolet radiation, it is ideally suited to long-term use in glazing systems.
The introduction of polyamide thermal breaks transformed aluminium glazing. It allowed manufacturers to retain the slim, strong profiles designers value while achieving thermal performance levels previously associated only with timber or uPVC frames.
How a Thermal Break Aluminium Window Performs
A thermal break aluminium window performs very differently from a non-insulated aluminium frame. By reducing heat transfer through the frame, it improves the overall U-value of the window or rooflight. This means less heat is lost in winter and less unwanted heat enters in summer.
Importantly, the benefits are not limited to energy efficiency. Internal frame temperatures remain higher, improving comfort near the window and reducing draught-like sensations caused by cold radiation. Warmer internal surfaces also reduce the likelihood of condensation forming on frames, a common problem with older aluminium systems.
When combined with modern double or triple glazing, low-emissivity coatings, and warm-edge spacers, thermally broken aluminium frames can achieve excellent whole-unit thermal performance.
Insulated Rooflight Frames and Their Importance
Rooflights present unique thermal challenges. Because they are horizontal or near-horizontal, they lose heat more rapidly than vertical windows. Warm air rises and pools against the glass, increasing heat transfer, while night-sky radiation further cools the external surface.
An insulated rooflight frame is therefore critical. Without a thermal break, the aluminium frame becomes one of the coldest elements in the room. This often results in condensation forming first on the frame rather than the glass, leading occupants to assume the rooflight is leaking.
Thermally broken rooflight frames help maintain internal surface temperatures, reduce cold bridging, and significantly lower the risk of condensation-related issues.
Condensation on Frames: Causes and Consequences
Condensation on frames occurs when warm, moisture-laden indoor air comes into contact with a surface that is below the dew point temperature. Aluminium frames without thermal breaks cool quickly in cold weather, making them prime locations for condensation.
The consequences go beyond visible water droplets. Persistent condensation can damage internal finishes, stain plasterboard, degrade sealants, and encourage mould growth. Over time, this can affect indoor air quality and lead to costly repairs.
Thermal breaks reduce these risks by keeping internal frame surfaces warmer. While no frame can completely eliminate condensation in extremely humid conditions, a thermally broken aluminium frame significantly reduces its frequency and severity.
Thermal Performance Comparison
The impact of thermal breaks on frame performance is substantial, as shown in the table below.
|
Frame Type |
Thermal Break Type |
Typical Frame U-Value (W/m²K) |
Condensation Risk |
|
Non-insulated aluminium |
None |
5.0 – 6.0 |
Very high |
|
Standard thermally broken aluminium |
Polyamide |
1.8 – 2.2 |
Moderate |
|
High-performance insulated aluminium |
Multi-zone polyamide |
1.0 – 1.4 |
Low |
This comparison highlights why non-insulated aluminium frames are no longer suitable for most residential applications.
Building Regulations and Energy Efficiency
Modern building regulations place increasing emphasis on energy efficiency and carbon reduction. In many regions, compliance with thermal performance requirements is effectively impossible without thermally broken aluminium frames.
Regulations typically focus on whole-window or whole-rooflight U-values, not just the glass. This means frame performance is just as important as glazing specification. A thermal break aluminium window is therefore essential for meeting regulatory targets and achieving building control approval.
Common Misconceptions About Thermal Breaks
One common misconception is that thick or triple glazing alone can solve thermal problems. While high-performance glass is important, it cannot compensate for a poorly insulated frame. Heat loss and condensation will still occur through the aluminium if it is not thermally broken.
Another misconception is that aluminium is inherently unsuitable for energy-efficient buildings. Modern thermally broken aluminium systems have proven that this is no longer true. With the right design, aluminium can combine excellent thermal performance with long-term durability and contemporary aesthetics.
Thinking about upgrading your rooflight or glazing system? Contact our team for expert advice on thermally broken aluminium solutions.
Choosing the Right Thermal Break Aluminium Window
When specifying aluminium glazing, it is essential to look beyond appearance. Key considerations include declared frame U-values, the type and width of the thermal break, independent thermal testing, and suitability for rooflight applications.
A well-designed thermal break aluminium window should balance structural performance with thermal efficiency, ensuring comfort, durability, and compliance over the life of the building.
Conclusion
Thermal breaks have revolutionised aluminium glazing. By addressing aluminium’s inherent thermal conductivity, they have transformed a once thermally inefficient material into a high-performance solution suitable for modern buildings.
The thermal break aluminium window, particularly when incorporating a polyamide thermal break, prevents heat loss, reduces cold bridging rooflights, improves insulated rooflight frame performance, and minimises condensation on frames. In today’s regulatory and environmental context, thermal breaks are not a luxury or optional extra. They are essential.
Investing in thermally broken aluminium frames is an investment in comfort, energy efficiency, and long-term building performance. If you are considering aluminium windows or rooflights, ensuring they include a properly designed thermal break should be a top priority.
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