Thermal Bridging Calculations

Thermal bridging calculations — also known as cold bridging analysis — identify and quantify heat loss at weak points in your building's insulation. UK Building Compliance carries out Psi-value calculations as part of your Part L compliance, helping you optimise your construction details and achieve better SAP or SBEM scores. As registered assessors with Stroma, we deliver accurate thermal bridging analysis that can significantly improve your building's energy performance.

What Are Thermal Bridging Calculations?

Thermal bridging calculations assess the heat loss that occurs at junctions and weak points in a building's insulation layer. A thermal bridge (or cold bridge) occurs wherever the continuous insulation envelope is interrupted — typically at corners, where the roof meets the walls, around window and door openings, or where an element with higher thermal conductivity penetrates the insulation.

The calculations determine the linear thermal transmittance (Psi-value) at each junction, expressed in W/mK. These values are then used to calculate the overall heat transfer coefficient (HTB value), which directly affects your SAP or SBEM score. Lower Psi-values indicate better thermal performance at junctions, leading to improved energy efficiency ratings and a higher EPC rating.

By accurately modelling thermal bridges rather than relying on default values, you can often demonstrate significantly better performance — potentially avoiding the need for more expensive upgrades to insulation, glazing, or heating systems elsewhere in the design.

Why Do You Need Thermal Bridging Calculations?

Thermal bridging calculations are required by Part L of the Building Regulations for new builds (L1A for dwellings, L2A for non-dwellings). They form an integral part of the SAP or SBEM assessment and directly influence whether your building achieves compliance.

Under the 2021 Part L amendments, the energy performance standards for new buildings have become significantly more demanding. Default thermal bridging values are deliberately conservative, meaning that buildings assessed using defaults often struggle to meet the required targets. Bespoke thermal bridging calculations allow you to demonstrate the actual performance of your construction details, which is almost always better than the default assumptions.

Poorly managed thermal bridges do not just affect compliance — they can also cause condensation, mould growth, and cold spots in the finished building. By addressing thermal bridging at design stage, you improve both the regulatory compliance and the long-term performance of the building for its occupants.

Our Thermal Bridging Calculations Process

UK Building Compliance provides thermal bridging analysis as a standalone service or as part of your wider SAP or SBEM calculations package.

1. Drawing review — You provide a complete set of architectural plans including floor plans, elevations, sections, and construction detail drawings. Our team identifies all thermal bridge junctions that require analysis.
2. Junction measurement — We measure the lengths of all thermal bridge junctions throughout the building, including wall-to-floor, wall-to-roof, wall-to-wall corners, window and door jambs, heads and sills, and any other relevant junctions.
3. Psi-value assessment — We determine the linear thermal transmittance (Psi-value) for each junction using accredited construction details or bespoke modelling as appropriate. Where your construction details match accredited details, we apply the published Psi-values. For non-standard details, we can arrange bespoke thermal modelling.
4. HTB calculation — The junction lengths and Psi-values are combined to calculate the overall HTB value, which is then input into your SAP or SBEM assessment.
5. Optimisation advice — If your thermal bridging performance needs improvement, we advise on practical construction detail changes that can reduce Psi-values and improve your overall compliance position.

What's Included

• Identification and measurement of all thermal bridge junctions
• Psi-value assessment using accredited construction details
• Overall HTB value calculation for input into SAP or SBEM
• Comprehensive thermal bridging report
• Design advice on optimising construction details to reduce heat loss
• Integration with your SAP calculations or SBEM calculations
• Guide pricing from £125 per junction

Who Needs Thermal Bridging Calculations?

Thermal bridging calculations are required for all new-build construction projects:

• New-build dwellings — All new homes require thermal bridging analysis as part of L1A SAP calculations to demonstrate Part L compliance.
• New commercial buildings — Non-domestic new builds require thermal bridging analysis as part of L2A SBEM calculations.
• Projects using non-standard construction — Timber frame, SIPs (structural insulated panels), ICF (insulated concrete formwork), and other modern methods of construction benefit particularly from bespoke thermal bridging analysis.
• Projects struggling to meet Part L targets — If your initial SAP or SBEM assessment shows marginal compliance, improved thermal bridging values can often bridge the gap without requiring expensive specification changes.

Architects, developers, housebuilders, and structural engineers all benefit from accurate thermal bridging calculations as part of the design and compliance process.

Why Choose UK Building Compliance?

UK Building Compliance has extensive experience delivering thermal bridging calculations for a wide range of construction projects. Our assessors are registered with Stroma and hold additional accreditations with ATTMA, ABBE, BPEC, Elmhurst, and UKAS.

We integrate thermal bridging analysis seamlessly with your wider compliance package, ensuring that junction values are accurately reflected in your SAP or SBEM assessment. Our consultancy approach means we actively advise on how to improve construction details to achieve better Psi-values — not just report the numbers.

Based in Hinckley, Leicestershire, we provide nationwide coverage with competitive pricing. Combine your thermal bridging calculations with SAP calculations, air tightness testing, and EPC production for a complete, coordinated compliance service. Call 01455 242297 for a free quote.