Thermal Bridging Calculations

Under Part L of the Building Regulations, thermal bridging must be considered in Standard Assessment Procedures (SAP) and Simplified Building Energy Model (SBEM) calculations.

Thermal Bridge Calculations – Finite Element Analysis (FEA)

Thermal bridging results in heat loss through junctions in the building fabric. The junctions include wall-roof and wall-floor junctions, party walls, corners, cills, jambs, lintels, and any other significant junctions of the building fabric. Their effects are expressed as a linear thermal transmittance value. This is used to arrive at a Y-value: a factor, which allows calculation of the building’s overall heat loss through thermal bridges.

Stroma Tech has an experienced team of Thermal Modellers able to model both simple and complex details accurately in 2D and 3D to determine Ψ-values and temperature factors.

Thermal Bridging Calculations – Implications of Part L1A 2013

The assessment of thermal bridge performance now has a greater impact than ever before on SAP calculations, due to the 2013 revisions to Part L1A and the stricter energy efficiency and CO2 targets.

At present, there are essentially 2 methods by which thermal bridges can be entered into SAP calculations:

Performance Values

Performance values have been calculated by a person with suitable expertise and experience, in accordance with BR 497 (Conventions for calculating linear thermal transmittance and temperature factors). In this case, the values are not subjected to any penalty factors.

Calculated Performance

Calculated performance cannot be provided to support the assessment. In this case, it is assumed that y = 0.15; this is an onerous assumption that roughly equates to a greater than 50% increase in the heat loss through a junction.

Complementary Services

We provide a truly integrated assessment service to assist any type of project.

  • SAP
  • Part L Compliance
  • EPCs


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