Modern building regulations are placing increasing focus on whole-building energy performance, especially at junctions such as door and window openings where heat loss is often concentrated.
These areas can become weak points in cavity wall construction if thermal bridging is not properly addressed at the design stage.
Thermally broken lintels tackle this issue at the source. They upgrade junction performance without requiring changes to specification or installation methods.
Why Thermal Bridging Is Important
Thermal bridging happens naturally wherever building materials meet and heat can transfer more easily between them. In cavity walls, lintels are one of the main junctions where this occurs. They can have a noticeable impact on overall fabric performance if this is not taken into consideration early in design.
As Part L, SAP 10.3, and the Future Homes Standard continue to tighten performance requirements, controlling these weak points has become an important part of achieving compliance.
The focus at specification stage is therefore on reducing these weak points in a practical and buildable way.
What Is a Thermally Broken Lintel?
A thermally broken lintel is a structural lintel developed to reduce heat transfer at wall openings in cavity construction. Instead of a continuous steel connection between the inner and outer leaves, a TBL includes an insulating break within the unit, which limits heat flow through the junction.
Basically, a thermally broken lintel performs the same structural function as a standard steel lintel, but with much better thermal performance at a key junction in the building fabric.
Why Thermally Broken Lintels Matter
Thermal bridges can account for a significant proportion of heat loss in buildings, with junctions such as lintels and window heads identified as some of the most critical areas in cavity wall construction. And this makes compliance with Part L and SAP 10.3 more and more difficult. Thermally broken lintels are crafted to interrupt this heat path and provide better performance at the junction.
How Thermally Broken Lintels Work
Thermally broken lintels maintain structural performance while interrupting the path that heat would normally take through a continuous steel element.
A traditional steel lintel creates a direct connection between the inner and outer leaf of a cavity wall. This allows heat to transfer freely through the material and contributes to thermal bridging at the wall opening.
A thermally broken lintel changes this through a three-part system:
1. Outer leaf steel section provides structural support to the external wall
2. Insulating core (thermal break) reduces heat transfer between leaves
3. Inner leaf steel section supports the internal wall structure
The continuous steel-to-steel connection is removed. This means heat transfer is significantly reduced, but structural performance is unaffected.
For a more in-depth look at how this contributes to reducing thermal bridging and improving overall building carbon performance, see our piece on Reducing
What Makes Catnic Thermally Broken Lintels Different?
Thermal break design is used across the industry, but Catnic Thermally Broken Lintels are engineered to deliver a more complete and reliable level of performance.
What makes them different from partial thermal break designs is that Catnic TBLs are built with a full separation between inner and outer steel sections. This removes direct conductive paths through the lintel and allows a true thermal break through a high-performance EPS core.
This engineered approach is built around these features:
Complete thermal break construction
Catnic TBLs use an EPS insulating core positioned between the inner and outer leaf steel sections. This ensures there is no continuous steel-to-steel connection through the unit.
Independently verified performance data
Each lintel is modelled and independently verified by thermal specialists, which gives you reliable performance data for specification purposes.
Normal psi values range from 0.02–0.05 W/mK depending on cavity width and wall build-up.
Design for compliance and specification confidence
Catnic TBLs are designed to support Part L requirements, SAP 10.2 assessments and the Future Homes Standard, and so guarantee predictable performance across many different residential construction types.
Find out more about how lintels contribute to meeting Part L and Future Homes Standard requirements.
Consistent installation method
Despite their superior thermal performance, Catnic TBLs install in the same way as standard cavity wall lintels. They need no specialist detailing or changes to your construction sequencing.
Benefits of Thermally Broken Lintels
Thermally broken lintels have many advantages. Let’s look at some of the key benefits:
• Improved thermal performance at openings where heat loss tends to be concentrated
• Enhanced internal surface conditions around lintel junctions
• Elevated confidence that overall fabric performance targets will be met
• More predictable energy performance outcomes at the design stage
• Standardised installation methods with no additional site complexity
For more details on the advantages of thermally broken lintels, see our guide on 5 Benefits of Using Thermally Broken Lintels.
Catnic's Thermally Broken Lintel Range
Catnic Thermally Broken Lintels are available across a wide range of cavity widths and load capacities, all supporting residential and low-rise commercial construction requirements.
Catnic also offers buy direct options to support faster specification and streamlined ordering.
Our options include:
• 90 - 105mm cavity
• 110 - 125mm cavity
• 130 - 145mm cavity
• 150 - 165mm cavity
• 170 - 185mm cavity
• 190 - 205mm cavity
• 210 - 225mm cavity
Along with variations in outer leaf and inner leaf elements to meet a full range of wall construction types
Each type is developed to give you both structural reliability and thermal performance appropriate to its application.
Explore the full range of Catnic Thermally Broken Lintels available across multiple cavity widths and performance specifications.
Thermally Broken vs Standard Lintels
There are clear differences between thermally broken and standard lintels. Traditional steel lintels are structurally effective but can create a direct thermal path through the wall opening, whereas thermally broken lintels maintain structural performance while notably improving junction efficiency.
Here is a quick table of comparison for your reference:
| Standard Steel Cavity Wall Lintel | Thermally Broken Cavity Wall Lintel | |
| Thermal bridging | High | Considerably reduced |
| psi value | Higher | Usually 0.02 - 0.05 W/mK |
| Temperature factor | Lower | Improved (up to 0.95) |
| SAP impact | Can negatively affect results | Support compliance |
| Condensation risk | Higher junctions | Reduced internal surface |
| Installation method | Standard | Standard |
Who Are Thermally Broken Lintels For?
Thermally broken lintels are used across a variety of residential and low-energy building projects, especially those where fabric performance and regulatory compliance are a priority.
Architects and designers
Thermally broken lintels help architects and designers refine fabric performance by limiting thermal bridging at openings and strengthening overall building efficiency. They also offer reliable performance data that can be used during design development and specification. Find more technical resources, CPD materials and guidance documents at the Catnic resources hub.
SAP assessors
For SAP assessors, independently verified psi values provide reliable inputs for thermal modelling, SAP calculations and wider compliance assessments. This helps a SAP assessor improve the accuracy of energy performance results, keeping any uncertainty in assessment work to a minimum, and making compliance calculations easier to manage throughout the design process. A PSI value calculator is also available to support detailed modelling and specification decisions.
Builders and contractors
For builders and contractors, thermally broken lintels install in the same way as standard lintels, which helps keep work on site efficient while still meeting tighter performance requirements.
Merchants
For merchants, thermally broken lintels sit within a growing category driven by demand for more energy-efficient construction products. They offer strong specification potential across residential projects, especially as tighter building regulations continue to influence material choices.
Homeowners
For end users, thermally broken lintels help create a more comfortable living environment as they decrease heat loss around openings and boost overall energy efficiency throughout the home.
For more detailed specification guidance, see Specifying Thermally Broken Steel Lintels.
Why Choose Catnic?
Catnic has been engineering steel lintels for over 50 years and supports construction projects across the UK with proven structural performance and dependable design.
Our thermally broken lintel range builds on that experience as it delivers a step forward in lintel performance. Catnic lintels blend trusted structural capability with substantially better thermal efficiency for modern building requirements.
Explore our full range of thermally broken lintels, buy direct, or contact the Catnic team today.
More...
Discover our resources below for more guidance on thermally broken lintels, thermal performance, and specification and regulatory requirements.
Understanding thermally broken lintels
Thermally Broken Lintels Explained
Why Thermally Broken Lintels Are a Game-Changer
The Types of Lintels Explained
Benefits and performance
5 Benefits of Using Thermally Broken Lintels
Specifying Thermally Broken Lintels to Reduce Thermal Bridging and Achieve Carbon Gains
4 Reasons to Specify a Catnic Thermally Broken Lintel
Specification and compliance
Building Regulation changes: Using lintels to reduce thermal bridging heat losses
Specifying thermally broken steel lintels for residential construction
When is a Thermally Broken Lintel not a Thermally Broken Lintel?
CPD and professional guidance
How Thermally Broken Lintels Support Part L Improvements for Future Homes Standard
Why Do I Need a Thermally Broken Lintel
FAQs About Thermally Broken Lintels
A thermal break is an insulating barrier within a building component that reduces the transfer of heat between conductive materials and helps enhance overall energy efficiency.
Thermally broken lintels reduce heat loss at wall openings, strengthen SAP performance, lower condensation risk and support compliance with modern building regulations.
You can use TBLs above door and window openings in cavity wall construction in residential and low-rise commercial buildings.
Thermally broken lintels are not strictly required by Part L, but they are often used to reduce thermal bridging and support compliance with the regulation’s energy efficiency targets.
No, thermally broken lintels are built to be installed in the same way as standard steel lintels, with no changes to usual construction methods.
Catnic Thermally Broken Lintels are available across a wide range of cavity widths, from 90mm up to 250mm, to suit all modern residential and low-energy wall constructions.
Thermally broken lintels decrease heat loss by introducing an insulating thermal break within the lintel. This interrupts the steel-to-steel connection between the inner and outer leaves of the wall and limits thermal bridging.
Installation is generally the same as a standard lintel, but it’s important to follow the installation guidance and ensure correct positioning within the cavity wall build-up. You should also maintain the continuity of insulation around the opening to get the best out of your thermal performance.
Catnic lintels are used to provide structural support over openings such as doors and windows in masonry construction. Our lintels help transfer loads safely while maintaining the integrity of the wall and are crafted to deliver reliable performance for many residential and commercial building projects.
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