Accurate thermal bridge analysis to support energy performance and compliance.
Thermal bridging can have a significant impact on a building’s energy performance, contributing to increased heat loss and higher energy demand. Psi-values (ψ-values) quantify this linear heat loss at junctions within the building fabric, providing a more accurate representation of real heat transfer than default assumptions.
MES Building Solutions deliver bespoke 2D and 3D psi-value calculations to support Part L compliance, SAP and SBEM assessments, and fabric-first design strategies. Our calculations help reduce reliance on conservative default values, improve overall building performance, and support proportionate specification across the rest of the building envelope.
Compliant Calculations
Calculated in line with Part L and SAP requirements
2D & 3D Thermal Modelling
Appropriate modelling of junctions based on complexity and design detail
Energy Focused
Clear outputs that directly inform SAP, SBEM, and Part L compliance
Detail-Led Improvements
Assessment and refinement of junction details to reduce heat loss
When Psi-Value Calculations are Needed
Thermal bridging calculations are typically required where improved accuracy is needed beyond default ψ-values, or where fabric performance plays a key role in achieving compliance.
Without calculated Psi-values, default values must be applied within SAP and SBEM, often resulting in higher energy demand and increased pressure on other elements of the design to achieve compliance.
Our Psi-Value Calculation Process
01
Junction Detail Review
Review of construction details and key thermal bridges
02
Thermal Modelling
2D or 3D modelling of junctions using specialist software
03
Performance Review
Assessment of heat loss and internal surface temperatures
04
Reports & Support
Clear documentation with recommendations for performance improvement
What Our Calculations Cover
Our Psi-value calculations include:
Related Building Physics Services
Additional services and guidance on the topic: