Why do junctions need separate attention?
Changes in geometry and material continuity at window reveals, floor edges, balconies, parapets and wall-to-roof junctions can create localised heat-flow paths. These details can affect both overall heat loss and minimum internal surface temperature. A nominal insulation thickness alone cannot describe the performance of every junction.
What does ISO 10211 address?
ISO 10211:2017 specifies two- and three-dimensional modelling approaches for calculating heat flows and surface temperatures at thermal bridges. Depending on the project, outputs may include a linear thermal transmittance (ψ-value) and information needed to evaluate a detail's local surface-temperature performance.
A useful calculation starts with an agreed drawing and credible inputs: the actual build-up and geometry, material properties, boundary conditions and intended construction continuity. A model represents the detail and assumptions provided; it does not by itself prove how an existing junction was installed.
How might a model support a client?
- Design review: compare proposed window-reveal, slab-edge or parapet details before installation.
- Existing building investigation: compare plausible build-ups or remedial options where a cold junction has been reported, with limitations stated.
- Reporting: separate a calculated result from measured site temperatures and from any conclusion about a concealed defect.
Where there is a concern about condensation or mould, surface-temperature calculations may need to be considered alongside indoor temperature and humidity using an appropriate risk-assessment method.
Do I need a thermal-bridge calculation?
Send Vertex a drawing or sketch, wall and insulation build-up, junction dimensions, intended purpose and any site observations. We can discuss an appropriate 2D junction review or calculation and define the deliverable before quoting. A project requiring formal third-party certification or a particular assessor's sign-off must be identified at the outset.
Primary reference: ISO 10211:2017 — heat flows and surface temperatures at thermal bridges