Build Comply

PSI Value Thermal Bridging Calculation

SAP Calculations

New-build, Conversions, Extensions, Over-glazing and Retrofit.

psi value thermal bridging calculation modelled measured values

Do you need calculated PSI-values for your Thermal Bridging Junctions?

PSI value calculations for building regulations can be quite technical. This can cause delays or frustration for technical teams, house builders, architects and SAP assessors preparing to pass the Standard Assessment Procedures (SAP) assessment.

Building Compliance Testing Limited can provide you with a fast and cost effective Elmhurst Certified SAP Calculations.

Learn more in the below sections as the requirements for a PSI values and thermal bridging calculations are varied dependant on your project type.

What Are PSI Values?

PSI values (Ψ-values) measure the additional heat loss at junctions where different building elements meet—such as wall-to-floor or wall-to-roof connections. Unlike U-values, which assess uniform surfaces, PSI values focus on non-repeating thermal bridges, where geometry or material changes increase heat transfer.

  • Measured in: Watts per meter-Kelvin (W/mK)
  • Indicates: Heat loss per meter of junction per °C temperature difference

Why Tackling Thermal Bridging Matters

  • ✅ Accurate Heat Loss Assessment
    PSI values provide a more realistic picture of thermal performance than U-values alone.

  • ✅ Improved Energy Efficiency
    Identifying and mitigating thermal bridges helps reduce overall heat loss.

  • ✅ Regulatory Compliance
    Required for SAP calculations to demonstrate compliance with Part L.

  • ✅ Cost Savings
    Reducing thermal bridging can lower heating costs and reduce insulation requirements elsewhere.

How We Calculate PSI Values

We use industry-leading software to model junctions in detail:

  • 📐 Detailed Modeling: Incorporating material properties and junction geometry
  • 🔁 Accurate Simulation: Simulating real-world heat flow through junctions
  • 🧩 Bespoke Calculations: Tailored to your specific building details—no reliance on generic values

Why Choose Us?

  • 🏗️ Expertise in Building Compliance Testing
  • 🧪 Precision Thermal Modeling
  • 📄 Fully Documented Reports for SAP Assessments
  • 🕒 Fast Turnaround & Competitive Pricing