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Hi-Therm Lintels

Keystone has redefined lintel performance with Hi-therm+, the low cost solution to reduced Carbon Emissions and improved Fabric Energy Efficiency.

#1 low cost solution to reduce carbon emissions. The genius is in our patented polymer isolator.

Hi-therm+ lintels are an award-winning innovation in steel lintel design, developed to address one of the most significant sources of heat loss in modern buildings: thermal bridging at window and door openings.

At the heart of the system is a patented polymer thermal isolator that separates the inner and outer steel sections of the lintel. This simple but highly effective innovation dramatically reduces heat transfer while maintaining the structural strength and practicality of a steel lintel.

The result is a smarter lintel solution that helps reduce carbon emissions, improve fabric performance and support compliance with Building Regulations Part L — without adding complexity on site.
Hi-therm+ lintels are up to five times more thermally efficient than standard steel lintels, making them one of the most effective ways to improve the thermal performance of the building envelope.

Key Benefits

  • The number one low-cost solution to reduce carbon emissions
  • Up to 5× more thermally efficient than a standard steel lintel
  • Dramatically reduces thermal bridging at openings
  • Psi values 0.03–0.06 W/mK
  • Supports SAP and Part L compliance
  • One-piece lintel design for simple installation

Innovation at the core of Hi-therm+

Traditional steel lintels create a thermal bridge because steel readily transfers heat through the building envelope.

Hi-Therm+ overcomes this with a patented hybrid design that combines galvanised steel, a rigid polymer thermal isolator and integrated insulation within a single factory-manufactured lintel.

By separating the inner and outer steel sections, the patented polymer thermal isolator interrupts the thermal path through the lintel, while the integrated insulation further enhances thermal continuity across the cavity.

Together, these three components are the Genius Inside Hi-Therm+, delivering exceptional thermal efficiency while maintaining the structural performance, simplicity and buildability of a one-piece steel lintel.

Key Components

  • Integrated insulation – Pre-fitted expanded polystyrene (EPS) insulation improves thermal continuity across the cavity and helps minimise heat loss.
  • Polymer thermal isolator – A patented rigid polymer thermal isolator separates the inner and outer steel sections, creating an effective thermal break that significantly reduces thermal bridging.
  • Galvanised steel structure – High-strength galvanised steel provides the strength, durability and structural performance expected from a Keystone steel lintel.

Hi-therm+ offers a cost effective solution to lowering carbon emissions within SAP, offering significant savings compared to other popular alternatives.

A proven solution to thermal bridging

Thermal bridging at junctions can have a significant impact on the energy performance of modern buildings.

In well-insulated homes, up to 30% of heat loss can occur through non-repeating thermal bridges, such as window and door openings.

Hi-therm+ lintels are engineered to dramatically reduce this effect.

With Psi values as low as 0.03 – 0.06 W/mK, Hi-therm+ lintels meet the Appendix R values required within SAP calculations, supporting compliance with Building Regulations Part L.

They can also improve junction Psi values by up to 15%, helping designers achieve fabric energy efficiency targets through a fabric-first approach.

By reducing thermal bridging at openings, Hi-therm+ lintels allow housebuilders to meet performance targets without relying on more expensive design changes.

Specification Benefits

  • Helps improve SAP calculations
  • Supports fabric-first compliance strategies
  • Reduces carbon emissions through better fabric performance
  • Future-ready for evolving building regulations

High performance without site complexity

Hi-therm+ lintels are engineered to deliver high thermal performance while maintaining simple installation on site.

The one-piece lintel design installs in the same way as a traditional steel lintel and requires no specialist equipment or skills.

Unlike split lintel systems that require multiple components and additional detailing, the Hi-therm+ design simplifies installation and improves stability during the build process.

The structurally superior top-hat design provides inherent stability between the internal and external leaves, helping ensure consistent build quality and faster installation.

Because Hi-therm+ works with standard construction methods, builders can benefit from improved thermal performance without changing existing work practices.

Key Advantages

  • Installs like a traditional steel lintel
  • No specialist tools or skills required
  • One-piece design simplifies installation
  • Faster installation compared with split lintel systems
  • Consistent build quality and reduced site detailing

Need to calculate PSI values?

Use our free PSI Value Calculator to assess thermal bridging and calculate accurate PSI values for your project.

Leading the pack in reducing carbon emissions

Discover why Hi-Therm+ continues to set the benchmark for thermally efficient steel lintels.

Why choose Hi-Therm Lintels?

Hi-Therm+ combines exceptional thermal performance with proven structural capability, helping designers, specifiers and housebuilders build more energy-efficient homes.

Up to 5× More Thermally Efficient

Hi-Therm+ is up to five times more thermally efficient than a standard steel lintel. Its patented thermal isolator and insulation help reduce thermal bridging and improve overall fabric performance.

Lower Psi Values

With Psi values typically between 0.03–0.06 W/mK, Hi-Therm+ helps optimise SAP calculations and supports compliance with demanding energy performance standards.

One-Piece Design

Unlike two-part thermal lintels, Hi-Therm+ is supplied as a single factory-manufactured unit, making installation quicker while reducing the risk of on-site errors.

Cost-Effective Fabric First Solution

Improve thermal performance without expensive specification changes elsewhere. Hi-Therm+ offers a practical, cost-effective way to reduce heat loss through the building fabric.

Full Structural Performance

Available in standard, heavy and extra heavy duty loadings, Hi-Therm+ delivers the structural performance expected from a steel lintel with significantly improved thermal efficiency.

Extensive Product Range

Available in a comprehensive range of profiles, load capacities and stainless steel options, making it easy to specify the right Hi-Therm+ lintel for your project.

BBA Approved

Hi-Therm+ is independently BBA certified, providing confidence in its structural, thermal and fire performance through rigorous third-party assessment.

Technical Support from Specification to Site

Our engineers provide specification guidance, schedule preparation and technical support to help ensure the right Hi-Therm+ lintel is selected every time.

Use our Hi-Therm lintel selector

Step 1
Step 2
13 products available
Product Outer leaf Cavity range Inner leaf Loading conditions Max length
HT/HD+ 100
HT/HD+ 100
102 90-105 100 Heavy Duty 3,600 View
HT/HD+ 110
HT/HD+ 110
102 110-125 100 Heavy Duty 3,600 View
HT/HD+ 130
HT/HD+ 130
102 130-145 100 Heavy Duty 3,600 View
HT/HD+ 150
HT/HD+ 150
102 150-165 100 Heavy Duty 3,600 View
HT/S+ 100
HT/S+ 100
102 90-105 100 Standard 4,200 View
HT/S+ 110
HT/S+ 110
102 110-125 100 Standard 4,200 View
HT/S+ 130
HT/S+ 130
102 130-145 100 Standard 4,200 View
HT/S+ 150
HT/S+ 150
102 150-165 100 Standard 4,200 View

We’ve used Keystone Lintels as a supplier from early as 2002 and in 2014 made the switch to their cost effective Hi-therm+ lintels. We understood then as we do now the importance of adopting a fabric first sustainable design to deliver better performing energy efficient homes.

Hi-therm+ lintels are a key component in our approach in working towards the governments net-zero carbon emissions goal by 2050.

Neil Hindle

Buyer

Rowland Homes

Trusted by Housebuilders

Hi-Therm+ is specified on developments to improve thermal performance, simplify compliance and deliver energy-efficient homes.

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