U-Value Calculations

Building-envelope U-values

U-values quantify heat transfer through the building envelope and provide a fundamental measure of thermal performance.

The calculation considers the complete construction build-up, including material properties and thicknesses. Depending on the construction, it can also account for repeating thermal bridges and other elements affecting overall performance.

U-value calculations can be carried out for

• Solid and framed wall assemblies
• Rainscreen façade constructions
• Curtain-wall framing and transoms
• Typical façade bays
• Other building-envelope assemblies

More complex façade systems

Where a simple one-dimensional calculation is not sufficient, U-value assessment can be combined with 2D or 3D modelling. This incorporates framing, connections, brackets and other heat-flow paths where required.

A typical assessment may combine U-value, Psi-value and Chi-value calculations with 2D modelling and 3D finite-element thermal modelling. The appropriate methodology is selected according to the construction and required assessment.

Curtain-wall calculations

Curtain-wall systems require specific treatment of framing and glazing interfaces. Frame thermal performance and glass-to-frame linear transmittance can be calculated using the applicable methodology before being combined within the wider façade calculation.

What you receive

• Construction build-up and material properties
• Calculated U-value
• Relevant Psi- and Chi-values
• Thermal-model outputs
• Calculation assumptions and methodology
• Technical calculation report
• Results for an individual construction or wider assessment

What I need

• Construction drawings
• Wall or façade build-up
• Material specifications
• Insulation thicknesses and thermal conductivities
• Relevant framing, fixing or bracket information
• Required target U-value, where applicable
• Send the detail if the appropriate calculation method is unclear