Building Physics
Understand how heat moves through building-envelope junctions where insulation continuity is interrupted, using thermal bridge analysis to investigate heat flow, thermal transmittance and internal surface temperatures before critical details are locked in.
For architects, engineers, façade consultants, developers and project teams investigating slab edges, balconies, parapets, window and door junctions, façade connections, roof-wall junctions and structural penetrations. Thermal bridge modelling provides a closer view of how individual construction details affect thermal continuity where simplified assumptions may not adequately represent the junction.
Discuss Thermal Bridge AnalysisIn Brief
Thermal bridge analysis investigates how heat flows through building-envelope junctions where the continuity of insulation is interrupted or where materials, geometry or structural connections create a more conductive path through the construction. Modelling these details provides a clearer understanding of how the junction behaves thermally before it is constructed.
A thermal bridge model can examine heat flow, internal surface temperatures and, where relevant, linear thermal transmittance or ψ-values. It can be applied to details such as slab edges, balconies, parapets, window and door junctions, façade connections, roof-wall junctions and structural penetrations where thermal continuity may be difficult to understand from drawings or material R-values alone.
Thermal bridge analysis is particularly useful where the performance of a specific junction needs closer investigation. It can identify concentrated heat-flow paths and cold internal surfaces, but it does not replace a broader moisture and condensation assessment, whole-building energy rating or occupied-space thermal comfort study. Instead, it provides detailed building-physics insight into the thermal behaviour of the construction detail itself.
Heat flow, thermal continuity, internal surface temperatures, linear thermal transmittance and ψ-values across specific building-envelope junctions and construction details.
Where slab edges, balconies, façades, windows, parapets, structural elements or other junctions interrupt the intended thermal envelope and the detail requires closer investigation.
It helps project teams see where heat is bypassing the intended insulation layer, understand the effect of a junction and compare detail changes before the construction is finalised.
Knowledge Navigation
Follow this guide to understand how thermal bridges affect building-envelope junctions, where they commonly occur, what thermal modelling can investigate and what project information is typically needed for a detailed analysis.
Foundation
Understand how modelling can investigate heat flow, thermal continuity, surface temperatures and linear thermal transmittance through specific building-envelope junctions.
Building Details
Explore common junctions including slab edges, balconies, parapets, window and door interfaces, façade connections, roof-wall junctions and structural penetrations.
Analysis Process
See how a construction junction is translated into a thermal model, how relevant conditions are defined and how heat-flow and surface-temperature results are interpreted.
Project Preparation
Review the sections, junction details, material build-ups, insulation layers and specifications typically needed to represent the construction accurately.
Analysis Process
Thermal bridge modelling creates a numerical representation of a building-envelope junction to show how heat moves through the materials and connections that form the detail. Instead of considering each material layer in isolation, the model examines the junction as a connected system, revealing where geometry, structural elements or interruptions in insulation create concentrated paths for heat flow.
The analysis begins with the construction detail itself. Material layers, insulation, structural components, thermal breaks and adjoining building elements are represented using the available drawings and specifications. Appropriate material properties and internal and external boundary conditions are then applied so the thermal behaviour of the junction can be calculated under defined conditions.
Depending on the geometry and purpose of the assessment, a junction may be investigated using two-dimensional or three-dimensional thermal modelling. Results can show heat-flow paths and temperature distribution through the detail, including internal surface temperatures. Where relevant to the assessment, the model can also be used to determine linear thermal transmittance, expressed as a ψ-value, or other junction-specific thermal quantities.
The results relate to the construction geometry, material properties and boundary conditions represented in the model. They therefore provide a detailed assessment of the defined junction rather than a prediction of whole-building energy use or occupied-space comfort. Where low surface temperatures raise a broader moisture question, thermal bridge analysis can also help identify where a separate moisture and condensation assessment may be appropriate.
Construction Detail
The relevant geometry, material layers, insulation, structural elements and thermal breaks are represented so the junction can be assessed as a connected construction detail.
Thermal Conditions
Material properties and appropriate internal and external boundary conditions establish the thermal conditions under which the construction junction will be analysed.
Analysis Results
Heat-flow paths and temperature distribution reveal how the junction behaves, where thermal continuity is interrupted and, where required, the effect of the detail on linear thermal transmittance.
Junction Analysis
Thermal bridge analysis provides a detailed view of how heat moves through a building-envelope junction. Rather than relying only on the thermal properties of individual materials, the analysis considers how geometry, structural connections, insulation layers and adjoining building elements interact within the complete construction detail.
What needs to be investigated depends on the junction and the project question. Modelling may be used to locate concentrated heat-flow paths, assess thermal continuity, calculate surface temperatures, quantify linear thermal transmittance or compare alternative detail configurations before the construction is finalised.
Heat Flow
Heat-flow modelling shows where a junction creates a more conductive path through the envelope and how heat moves through the connected materials and structural elements.
Thermal Continuity
The model can show how insulation, thermal breaks and structural components connect across the junction and where continuity is weakened by the construction geometry.
Surface Temperature
Temperature distribution across the detail can identify lower internal surface temperatures around corners, interfaces and other junctions where thermal bridging is concentrated.
Linear Thermal Transmittance
Where relevant, linear thermal transmittance can be calculated as a ψ-value to quantify the additional heat flow associated with a linear junction beyond the adjoining building elements.
Detail Comparison
Alternative insulation arrangements, thermal breaks, connection details or material configurations can be modelled under consistent conditions to understand how proposed changes affect the junction.
Cold-Surface Risk
Where modelling identifies low internal surface temperatures, the result can help determine whether the detail requires further investigation. Broader moisture behaviour is assessed separately through Moisture & Condensation Risk Analysis.
A useful thermal bridge study starts with a clearly defined junction and project question. Establishing what the team needs to understand — whether that is heat flow, a ψ-value, surface temperature or comparison between detail options — allows the model and reporting outputs to be aligned with the design decision being made.
Building Envelope Junctions
Thermal bridges commonly occur where the geometry, materials or structural connections of a building interrupt the intended insulation layer. These junctions can create a more conductive path between the inside and outside of the building, allowing heat to bypass parts of the surrounding thermal envelope.
Some thermal bridges are easy to recognise, such as a concrete balcony extending through an insulated façade. Others occur within more complex details where slabs, steelwork, window frames, façade systems or roof and wall assemblies meet. The effect depends on the geometry of the junction, the materials involved and how insulation and thermal breaks continue through the connection.
Reviewing these details during design allows the project team to investigate junctions that may have a meaningful effect on heat flow or internal surface temperatures before they become fixed construction details. Not every junction requires detailed modelling; the first step is identifying which connections warrant closer analysis.
Slabs & Balconies
Slab edges, balcony connections and projecting structural elements can create direct heat-flow paths where they pass through or interrupt the insulation layer.
Windows & Façades
Window and door junctions, façade connections, framing and fixing systems can introduce localised thermal bridges where different materials and envelope systems meet.
Roofs & Structural Junctions
Parapets, roof-wall junctions, steel members and structural penetrations can interrupt otherwise continuous insulation and create concentrated paths for heat flow.
A well-insulated wall, roof or façade can still contain a significant thermal bridge where materials and systems connect. Thermal bridge analysis looks at the complete junction rather than considering insulation values in isolation, helping the project team understand how the detail performs as it is actually intended to be constructed.
Junction Behaviour
Not every thermal bridge behaves in the same way. Some extend continuously along a junction, such as a slab edge, parapet or window perimeter. Others are concentrated around individual fixings, brackets, anchors or structural connections. Understanding the geometry of the detail helps determine how the thermal bridge should be represented and what information the analysis needs to provide.
Linear thermal bridges are typically associated with junctions that continue along a length of the building envelope. Where required, their additional heat flow can be expressed as linear thermal transmittance, or a ψ-value. Point thermal bridges occur at discrete locations and may require a different approach where heat flow extends in more than two dimensions.
The appropriate level of modelling depends on the geometry and the question being investigated. A relatively uniform junction may be represented using a two-dimensional section, while complex brackets, penetrations or three-dimensional connections may require a 3D model to represent the heat-flow path appropriately. The modelling approach should follow the detail rather than applying the same method to every junction.
Linear Junctions
Slab edges, parapets, window perimeters and other repeating junctions can create additional heat flow along a continuous length of the thermal envelope.
Point Junctions
Brackets, anchors, fixings and structural penetrations can create concentrated thermal bridges at individual locations rather than continuously along a junction.
2D & 3D Modelling
Two-dimensional modelling may suit junctions that remain consistent along their length, while more complex connections may require three-dimensional analysis to represent the thermal path accurately.
You do not need to decide whether a junction requires 2D or 3D modelling before sending the project information. The geometry of the connection, the available construction detail and the question the project team needs answered can be reviewed first, so the analysis is scoped around the junction rather than around a predetermined modelling method.
Design Development
A thermal bridge does not always require an entirely different construction system. Sometimes the important question is whether a change in insulation continuity, connection geometry, thermal break or material arrangement meaningfully changes the way heat moves through the junction. Thermal modelling allows these alternatives to be compared before the detail is finalised.
By modelling proposed options under consistent conditions, project teams can see how changes affect heat-flow paths, internal surface temperatures and, where relevant, linear thermal transmittance. This provides a clearer basis for discussing the thermal consequences of a detail rather than relying only on individual material properties or assumptions about how the junction will behave.
The purpose is not to prescribe the architectural or structural solution in isolation. Thermal bridge analysis provides building-physics evidence that can be considered alongside structural requirements, façade design, buildability, waterproofing, material selection and other project constraints as the detail develops.
Insulation Continuity
Where insulation stops, changes direction or passes around structural elements, alternative arrangements can be modelled to understand how effectively the thermal layer continues through the junction.
Typical comparisons may include:
Connections & Thermal Breaks
Structural and façade connections can be investigated to understand how changes to geometry, material pathways or thermal breaks affect heat transfer through the surrounding envelope detail.
Typical comparisons may include:
When alternative details are modelled using consistent geometry, material data and boundary conditions, the project team can see how the thermal behaviour changes between options. This can be particularly useful during design development, when junctions are still being coordinated and changes can be considered alongside the requirements of the wider project.
Thermal bridge analysis evaluates the thermal behaviour of the modelled junction. It does not replace structural engineering, façade engineering, waterproofing design or other specialist design responsibilities. Instead, it adds thermal performance evidence to the coordination of the construction detail.
Analysis Outputs
Thermal bridge analysis produces numerical and visual information describing how heat moves through a modelled building-envelope junction. Instead of reducing the detail to a single insulation value, the results can show how geometry, materials and structural connections affect heat flow and temperature distribution across the complete junction.
The outputs depend on the question being investigated. Some studies may focus on visualising heat-flow paths and internal surface temperatures, while others may require calculation of linear thermal transmittance, comparison between alternative details or closer examination of a particular part of the junction.
Defining the purpose of the analysis before modelling begins helps ensure that the model, calculations and reporting outputs are aligned with the design decision or technical question the project team needs to resolve.
Temperature Distribution
Temperature contours show how conditions vary across materials and junctions, making localised temperature changes within the construction detail easier to identify.
Heat-Flow Paths
Heat-flow visualisations help show where energy is moving through the junction and where structural or material connections create more conductive paths through the thermal envelope.
Surface Temperatures
Calculated internal surface temperatures can identify colder locations around corners, interfaces and connections where thermal bridging affects the temperature of the internal surface.
ψ-Values
Where required, a ψ-value can quantify the additional heat flow associated with a linear thermal bridge beyond the thermal performance of the adjoining building elements.
Detail Comparison
Results from consistently modelled alternatives can show how changes to insulation, thermal breaks, materials or connection geometry affect the thermal behaviour of the junction.
Technical Reporting
Reporting can document the modelled detail, assumptions, material properties, boundary conditions, relevant outputs and interpretation needed to understand what the analysis means for the project.
Temperature contours and heat-flow graphics are representations of calculated conditions within a defined model. They need to be read in the context of the construction geometry, material properties, boundary conditions and assumptions used in the analysis rather than treated as standalone evidence of how a building will perform under every condition.
A useful thermal bridge report therefore connects the numerical and visual outputs back to the junction being investigated. This helps the project team understand where thermal continuity is affected, how significant the modelled behaviour is to the question being considered and whether further detail development or investigation is warranted.
Project Suitability
Thermal bridge analysis is most useful when the thermal behaviour of a building-envelope junction cannot be understood confidently from material properties or simplified assumptions alone. It provides a closer view of how heat moves through the complete detail, particularly where insulation continuity is interrupted by geometry, structure or connections between different building systems.
Detailed modelling may be appropriate where a slab edge, balcony, parapet, window interface, façade connection, roof-wall junction or structural penetration creates a potentially significant heat-flow path. It can also support projects where surface temperatures need closer investigation, a ψ-value is required or alternative detail configurations need to be compared using consistent assumptions.
The decision to model a junction should begin with the project question rather than the modelling method. A focused analysis of a clearly defined detail is generally more useful than modelling multiple junctions without first establishing what the project team needs to understand, quantify or compare.
Interrupted Insulation
Slabs, steelwork, façade supports and other structural elements may pass through or around insulation, creating heat-flow paths that are difficult to assess from insulation values alone.
Complex Junctions
Window interfaces, parapets, façade connections and roof-wall junctions can combine multiple materials and geometries, making the resulting thermal path difficult to judge from drawings alone.
Surface Temperature
Modelling can calculate internal surface temperatures around a junction where the project team needs to understand the local effect of thermal bridging more closely.
ψ-Value Requirement
Where linear thermal transmittance needs to be established for a particular junction, detailed modelling can be used to calculate a project-specific ψ-value where appropriate.
Design Comparison
Alternative insulation arrangements, thermal breaks, connection geometries or material configurations can be compared to understand how each option changes the thermal behaviour of the junction.
Critical Detail
Analysis may be useful where the thermal behaviour of a particular junction affects an important design decision and simplified assumptions do not provide enough information to resolve it confidently.
Detailed thermal bridge modelling may add little value where the thermal behaviour of a junction is already adequately understood through established construction guidance, suitable reference data or information available for the proposed system. The level of analysis should remain proportionate to the detail and the decision it needs to support.
An initial review of the junction drawings, material build-ups, insulation strategy and project objective can help establish whether modelling is warranted, which detail should be assessed and what outputs would be useful to the project team.
Analysis Workflow
A thermal bridge analysis begins with the construction junction and the question the project team needs answered. This may be understanding a heat-flow path, investigating a cold internal surface, calculating a ψ-value or comparing alternative detail configurations before the design is finalised.
Relevant sections, construction details, material build-ups and insulation layers are reviewed before the junction is translated into a numerical thermal model. The geometry and material properties are represented at the level needed for the analysis, with appropriate internal and external boundary conditions applied to define the calculation.
Once the model has been calculated, heat flow, temperature distribution and other required outputs are reviewed against the original project question. The findings can then be documented and, where alternative details are being considered, used to compare how changes to the junction affect its thermal behaviour.
Step 01
Establish which junction needs investigation, why it matters to the project and whether the required outcome relates to heat flow, surface temperature, a ψ-value or comparison between detail options.
Step 02
Sections, junction drawings, material build-ups, insulation layers, structural elements and available specifications are reviewed to understand how the proposed detail is intended to be constructed.
Step 03
The relevant geometry, materials, insulation, thermal breaks and structural connections are represented in a two-dimensional or three-dimensional model appropriate to the junction.
Step 04
Material properties, internal and external boundary conditions and other relevant calculation assumptions are established for the defined analysis.
Step 05
The model is calculated and reviewed to understand heat-flow paths, temperature distribution, internal surface temperatures and any other quantities required for the assessment.
Step 06
Relevant numerical and visual outputs are interpreted against the project question and documented with the modelling assumptions, findings and any comparison between assessed detail options.
Thermal bridge analysis does not always end with the first model. Where an initial result identifies a significant heat-flow path or low surface temperature, the project team may choose to investigate a revised insulation arrangement, thermal break, connection geometry or other detail change.
Where alternatives are compared, the relevant modelling conditions should remain consistent so that differences in the results reflect changes to the construction detail rather than changes to the calculation approach. This allows thermal modelling to support an iterative design process while the junction is still being coordinated.
Project Inputs
The information needed for thermal bridge analysis depends on the junction being investigated and the question the project team needs answered. A slab edge, window interface or façade connection may each require different levels of detail, but the aim is the same: to represent the geometry, materials and thermal path of the proposed construction accurately enough for the required analysis.
You do not necessarily need a complete construction package before a junction can be reviewed. During design development, sections, preliminary details and known material build-ups may be enough to identify what can be modelled and what additional information is still required. More developed assessments may rely on coordinated construction details, specifications and confirmed material properties.
It is also useful to explain why the detail is being assessed. Knowing whether the project needs a ψ-value, surface-temperature review, comparison between alternatives or investigation of a particular heat-flow path helps determine which inputs are relevant and how the analysis should be scoped.
Junction Drawings
Relevant sections and construction details help define the geometry of the slab edge, balcony, parapet, window, façade, roof-wall junction or other connection being investigated.
Material Build-Ups
Information on concrete, masonry, insulation, framing, linings, cladding and other relevant layers helps establish how heat can move through the modelled construction.
Insulation & Thermal Breaks
Insulation type, thickness and position, together with any proposed thermal breaks, help define where the intended thermal layer continues and where it is interrupted.
Structural Connections
Details of slabs, steel members, brackets, anchors, fixings and other structural connections may be required where these elements pass through or connect across the thermal envelope.
Material Information
Product data, specifications and available thermal properties can help establish the material inputs used in the model. Where information is incomplete, any necessary assumptions should be identified as part of the analysis.
Project Question
The required outcome may be a ψ-value, surface-temperature assessment, investigation of a heat-flow path, comparison between detail options or another clearly defined thermal question.
If the detail is still developing, the available drawings and specifications can be reviewed first to establish whether they are sufficient for the intended analysis. Where important information is missing, the required material properties, dimensions or connection details can be identified before modelling proceeds.
As the design becomes more resolved, the thermal model can reflect updated junction geometry, confirmed materials or revised connection details where further analysis is required. This allows thermal bridge assessment to support both early design investigation and more developed construction details without requiring the same level of documentation at every project stage.
Model Definition
A thermal bridge model represents a defined construction detail under defined thermal conditions. To interpret the results properly, it is important to understand not only the geometry of the junction, but also the material properties, internal and external conditions and modelling assumptions used in the calculation.
These inputs establish how heat is able to move through the model. Thermal conductivity values influence heat transfer through individual materials, while boundary temperatures and surface conditions establish the thermal environment applied to the junction. Geometric assumptions determine which parts of the construction are represented and how they connect.
The resulting heat-flow and temperature calculations therefore relate to the conditions represented in the model. Clear documentation of those conditions is important when interpreting a ψ-value, surface temperature or comparison between alternative details, particularly where project information is still developing.
Material Properties
Thermal conductivity and other relevant material properties are assigned to insulation, concrete, masonry, metals, linings and other components represented within the junction.
Internal Conditions
Appropriate internal thermal conditions are applied so that heat flow and internal surface temperatures can be calculated for the purpose of the assessment.
External Conditions
External thermal conditions are defined according to the purpose and methodology of the analysis, establishing the temperature difference across the modelled construction.
Surface Conditions
Surface heat-transfer conditions are applied at relevant boundaries so the model can represent heat exchange between the construction and the adjoining internal or external environment.
Model Geometry
The model includes the dimensions, material layers, structural connections and adjoining elements needed to represent the thermal path through the junction without reproducing unrelated parts of the building.
Analysis Method
The modelling approach, level of geometric detail and required outputs should reflect whether the assessment is investigating heat flow, surface temperature, linear thermal transmittance or comparison between design options.
Where dimensions, material properties or other project information have not yet been confirmed, assumptions may be needed to complete the analysis. These should be identified clearly so the project team can distinguish confirmed design information from values or conditions introduced for modelling purposes.
If an uncertain input is likely to materially affect the result, the detail can be reviewed again when better information becomes available or alternative assumptions can be compared where appropriate. This is particularly important when the analysis is being used to compare design options or quantify the thermal effect of a specific junction.
Design Testing
When a junction is still being developed, thermal modelling can be used to test what happens when a specific part of the detail changes. A base detail can be compared with one or more alternatives to show whether a revised insulation position, thermal break, connection geometry or material pathway changes heat flow through the junction.
The clearest comparisons isolate the variable being investigated while keeping the relevant calculation conditions consistent. This makes it easier to distinguish the thermal effect of the proposed change from differences caused by unrelated modelling inputs.
Depending on the project question, the comparison may focus on heat-flow patterns, internal surface temperatures, linear thermal transmittance or a combination of outputs. The purpose is not simply to identify a numerically lower result, but to provide thermal evidence that can be considered alongside the other requirements of the construction detail.
Insulation Position
Alternative insulation positions, thicknesses or transitions can be compared where the thermal layer changes direction or passes around a structural connection.
Thermal Break
Different thermal break arrangements can be modelled to understand how their position, geometry or thermal properties affect heat transfer through the connection.
Connection Geometry
Changes to brackets, slab connections, framing or other junction geometry can be assessed where the physical connection creates an important pathway through the thermal envelope.
Material Pathway
Where highly conductive materials cross or connect through the envelope, alternative material arrangements can be tested to understand their influence on the modelled heat-flow path.
A useful comparison keeps the relevant boundary conditions, material properties and modelling approach consistent while changing the part of the detail being investigated. If several unrelated variables change at once, it becomes more difficult to determine which change is responsible for the difference in thermal performance.
The thermal results are one part of the design decision. A detail that changes heat flow may also affect structure, façade engineering, waterproofing, buildability, cost or architectural intent. Thermal bridge analysis provides evidence about the thermal consequence of the options so those wider decisions can be made by the project team with clearer information.
Analysis Boundaries
Thermal bridging and condensation can be related, but they are not the same building-physics question. Thermal bridge analysis investigates how heat moves through a junction and how that junction affects thermal continuity, heat flow and surface temperatures. Moisture and condensation risk analysis investigates how an assembly manages moisture under defined environmental conditions.
A thermal bridge model may identify a colder internal surface around a slab edge, window interface, parapet or structural connection. That result can be relevant to a moisture question because surface temperature influences condensation potential, but it does not by itself describe vapour movement, moisture accumulation or the wider hygrothermal behaviour of the assembly.
The appropriate analysis therefore depends on what the project team needs to understand. If the question concerns heat bypassing the intended thermal envelope, thermal bridge analysis is the relevant starting point. If the concern extends to condensation, vapour movement or moisture behaviour within the construction, a dedicated moisture and condensation assessment may be required.
Junction Thermal Behaviour
Thermal bridge analysis examines how geometry, materials and structural connections influence heat transfer through a defined building-envelope junction.
It primarily investigates:
Moisture Behaviour
Moisture and condensation risk analysis examines how environmental conditions and the properties of an assembly influence moisture behaviour within or at the surfaces of the construction.
It may investigate:
A thermal bridge analysis may identify a junction where thermal continuity is interrupted and the internal surface becomes significantly colder than surrounding areas. If the project question then extends to whether those conditions could contribute to condensation or moisture-related risk, the assessment may need to move beyond heat flow and surface temperature alone.
In that situation, the two forms of analysis answer different but connected questions. Thermal bridge analysis establishes what is happening thermally at the junction, while moisture and condensation risk analysis examines how the relevant assembly may behave when moisture, vapour and environmental conditions are considered.
Assessment Boundaries
Thermal bridge analysis and broader energy or compliance assessments can all consider the thermal performance of the building envelope, but they operate at different scales. Thermal bridge analysis examines what happens at a specific construction junction, while energy and compliance assessments consider how the building or envelope performs within a wider assessment framework.
A thermal bridge model can investigate heat flow through a slab edge, balcony, parapet, window interface, façade connection or other local detail. Depending on the purpose of the analysis, it may calculate surface temperatures or quantify the additional heat flow associated with a junction using a ψ-value. Broader energy assessments use different methods and inputs to evaluate building-level performance, energy demand or the requirements of a particular compliance pathway.
Thermal bridging may form part of the information considered within some building-fabric and energy assessment methods, but specialist junction modelling is not automatically required for every project. The applicable approach depends on the building type, construction, assessment method and project objective.
Junction-Level Performance
Thermal bridge analysis examines the local thermal behaviour of a defined building-envelope junction and the way geometry, materials and structural connections influence heat flow.
It may investigate:
Building-Level Assessment
Energy and compliance assessments evaluate building performance within the methodology, inputs and requirements of the relevant assessment or regulatory pathway.
Depending on the pathway, this may include:
A wall, roof or façade may have strong nominal insulation performance while still containing junctions that create additional heat-flow paths through the envelope. Where those junctions are relevant to the project, thermal bridge analysis can provide more detailed information about their local thermal effect than a material R-value or simplified envelope description alone.
That information may support a wider building-performance or compliance process where the applicable methodology requires it, but the thermal bridge analysis itself should not be treated as evidence that the whole building complies. Section J, JV3, NatHERS and other assessment pathways each have their own scope, inputs and requirements.
Result Interpretation
Thermal bridge analysis calculates how heat moves through a defined representation of a construction junction. The results describe the thermal behaviour of that model under the selected conditions rather than every variation that may occur within the completed building.
The usefulness of the analysis depends on how accurately the relevant geometry, material layers, structural connections and thermal properties represent the detail being investigated. Boundary conditions and modelling assumptions also influence how calculated heat flow, surface temperatures and ψ-values should be interpreted.
Thermal bridge results are therefore most useful when they remain connected to a clearly defined junction and project question. The modelled construction, assumptions and calculation conditions should be considered alongside the numerical and visual outputs rather than treating any single value or temperature contour in isolation.
Defined Junction
The analysis represents the geometry, material arrangement and connections included within the model. A different junction or construction configuration may produce different thermal behaviour.
Input Quality
Where dimensions, material properties or construction information are preliminary or incomplete, assumptions may be required. Those assumptions should be considered when the results are interpreted.
Model Resolution
The model needs sufficient geometric and material detail to represent the heat-flow paths relevant to the assessment without unnecessarily reproducing parts of the construction that do not affect the question.
Design Changes
Changes to insulation, thermal breaks, structural connections, material layers or junction geometry may affect whether an earlier thermal bridge model still represents the proposed construction.
Calculated Conditions
Calculated temperature distributions and surface temperatures relate to the thermal conditions represented in the model and should be interpreted within the purpose and methodology of the assessment.
Technical Interpretation
Temperature contours, heat-flow graphics and calculated values should be interpreted together with the junction geometry, material inputs, boundary conditions and original project question.
Thermal bridge analysis can show how a proposed junction is expected to behave when constructed as represented in the model. It does not confirm that insulation, thermal breaks, fixings or other components will be installed in exactly the same position or condition on site.
Where verification of the completed construction is important, appropriate site inspection, construction quality assurance or other project-specific verification may still be required. Thermal modelling and site verification answer different questions: one investigates the proposed thermal detail, while the other considers what has actually been built.
Project Planning
The time and cost of thermal bridge analysis depend on what needs to be investigated and how complex the relevant junctions are. A focused assessment of one clearly documented slab edge or window detail will usually involve a different scope from a project requiring multiple junctions, three-dimensional connections or comparison between several design alternatives.
The work may include reviewing construction details, confirming material build-ups, preparing the thermal model, assigning material properties and boundary conditions, completing the calculations and interpreting the required outputs. Where a junction is geometrically complex or project information is incomplete, additional preparation may be needed before meaningful modelling can begin.
A clear project question helps keep the scope proportionate. Identifying which junctions need analysis, what the project team needs to learn from them and whether the required output is a ψ-value, surface-temperature assessment, design comparison or broader technical report provides a clearer basis for programme and fee review.
Number of Junctions
A single critical junction requires a different scope from a façade or envelope review involving multiple slab edges, parapets, window interfaces, roof junctions or structural connections.
Junction Complexity
Simple continuous junctions may be relatively straightforward to represent, while brackets, structural penetrations, layered façade systems and irregular connections can require more detailed model preparation.
2D or 3D Analysis
A junction that can be represented appropriately in two dimensions may require a different modelling effort from a point connection or complex geometry where three-dimensional heat flow needs to be considered.
Design Alternatives
Comparing alternative insulation positions, thermal breaks, connection geometries or material arrangements may require additional models or calculation runs using consistent conditions.
Available Project Information
Clear junction drawings, dimensions, material build-ups and product information can reduce the additional review needed to establish the geometry and thermal properties used in the model.
Required Outputs
The scope may differ depending on whether the project requires heat-flow and temperature graphics, surface temperatures, ψ-values, comparison tables, technical interpretation or a more detailed reporting package.
A useful starting point is the detail or set of details that need investigation, together with the available drawings, material information and the reason the analysis is being requested. From there, the required modelling approach and outputs can be established without asking the project team to define the technical methodology themselves.
Where the design is still developing, an initial review can help identify which junctions warrant detailed modelling and what additional information is needed. This can keep the analysis focused on the details that matter to the project rather than modelling every envelope connection by default.
If a modelled junction changes substantially after the analysis has been completed, the effect of that revision may need to be reviewed. Confirming the relevant geometry and material build-up before detailed modelling can help reduce avoidable rework later in the project.
Project Coordination
Thermal bridges often occur where several parts of the design meet. A slab edge may involve structure, façade and insulation; a window junction may depend on frame position, wall build-up and installation geometry; and a parapet may bring together roof, wall and structural details. Useful analysis therefore depends on understanding the junction as a coordinated construction detail.
Different members of the project team may hold different parts of the information needed for the model. Architectural drawings can establish the intended geometry and envelope strategy, while structural and façade information may define the connections, brackets, fixings, materials and thermal breaks that create or interrupt the thermal path.
Thermal bridge analysis brings this information together to investigate the thermal behaviour of the junction. The findings can then return to the design team as evidence for coordination, while responsibility for architectural design, structural engineering, façade design, waterproofing and other specialist requirements remains with the appropriately appointed project disciplines.
Architectural Team
The architectural team can provide sections, junction details, wall and roof build-ups, window positions, insulation strategy and other information that establishes how the building envelope is intended to come together.
Structural & Façade Teams
Structural and façade consultants may define slabs, steelwork, brackets, anchors, façade supports, framing and other connections that influence the thermal path through a junction.
Thermal Analysis
The thermal model brings together the relevant geometry, material properties and calculation conditions to investigate heat flow, thermal continuity, surface temperatures and other required outputs for the defined junction.
Wider Project Team
The wider project team can consider the thermal findings alongside structure, façade performance, waterproofing, buildability, cost, architectural intent and other project requirements when deciding whether a detail should be revised.
Thermal bridge analysis can provide the greatest design value once the relevant envelope strategy and junction geometry are developed enough to support a meaningful model, but while there is still an opportunity to change the detail. At this stage, the analysis can help the project team understand a thermal issue before the connection becomes difficult to revise.
Starting very early may mean that important dimensions, materials or structural connections are still unknown. Waiting until documentation or procurement is substantially complete may leave fewer practical options if the analysis identifies a significant thermal path or a detail that warrants further development.
If you are unsure whether a junction is developed enough for analysis, the available detail can be reviewed first. This can establish what can already be assessed, what information is still needed and whether modelling now or at a later design stage would provide the more useful result.
Standards & Guidance Context
Thermal bridge analysis sits within a wider framework of international calculation standards, Australian building-fabric requirements and project-specific assessment methods. Which documents are relevant depends on why the junction is being analysed and how the results will be used.
A design team may need detailed numerical modelling of a particular junction, a linear thermal transmittance value, information for a broader energy assessment or evidence to support a specific project requirement. These purposes should be established before selecting the calculation method and reporting approach.
ISO 10211
ISO 10211 establishes specifications for two-dimensional and three-dimensional geometrical models used to calculate heat flow and surface temperatures through thermal bridges. It also provides a basis for deriving linear and point thermal transmittances and surface temperature factors.
ISO 14683
ISO 14683 addresses linear thermal transmittance for thermal bridges and provides simplified methods and default values. The appropriate method depends on the purpose of the assessment and the level of detail required for the junction being considered.
National Construction Code
Thermal bridging is considered within parts of the NCC building-fabric provisions. The applicable requirements and calculation approach depend on the building class, construction and compliance pathway, so the relevant project context should be established before determining what analysis is required.
NatHERS
NatHERS includes specific requirements for representing thermal bridging associated with repeating steel-frame elements where insulation is interrupted. This forms part of the NatHERS assessment methodology and should not be confused with specialist junction analysis undertaken for a separate building-physics question.
A request for a ψ-value, investigation of a cold internal surface, comparison of alternative junction details and assessment within a particular energy or compliance pathway may each require different inputs, calculation methods or reporting conventions. The existence of a thermal bridge does not by itself determine which standard or assessment pathway should be applied.
For this reason, the intended use of the results should be identified at the beginning of the assessment. The modelling scope can then be aligned with the relevant technical guidance, project requirements and level of calculation detail rather than applying the same method to every junction.
Design Questions
You do not need to know which thermal calculation or modelling method your project requires before asking for analysis. A more useful starting point is the construction detail and the question the project team needs to resolve.
Thermal bridge analysis can then be structured around that decision, whether the concern is a broken insulation line, a highly conductive connection, a colder internal surface, the thermal effect of a junction or the difference between alternative details.
The model can show how heat moves through a junction and identify conductive paths created by slabs, steelwork, brackets, framing or other elements that interrupt the intended insulation layer.
Where appropriate, analysis can quantify the additional heat flow associated with a linear junction using a ψ-value, providing more information than the thermal properties of the adjoining building elements alone.
Calculated temperature distributions can help identify locally colder internal surfaces around corners, interfaces and connections under the conditions represented in the thermal model.
Analysis can investigate how the insulation layer connects around slab edges, parapets, window openings, roof-to-wall junctions and façade interfaces, including locations where continuity becomes difficult to maintain.
Alternative insulation positions, thermal breaks, connection geometries or material arrangements can be modelled under consistent conditions to understand how a proposed revision changes the thermal behaviour of the detail.
An initial review can help determine whether a junction is adequately understood from the available construction information or whether numerical modelling would provide useful evidence for the design decision.
A project team may know that a balcony connection, slab edge, parapet or window detail needs closer investigation without knowing whether the appropriate next step is a two-dimensional model, three-dimensional analysis, ψ-value calculation, surface-temperature review or comparison between several design options.
Providing the available detail and explaining the decision that needs to be made is usually enough to begin. The modelling approach, required inputs and appropriate outputs can then be defined around the thermal question rather than asking the project team to specify the analysis method in advance.
Frequently Asked Questions
A thermal bridge is a part of the building envelope where heat can flow more readily than through the surrounding construction. This can occur where insulation is interrupted, where conductive materials pass through the thermal envelope or where the geometry of a junction changes the heat-flow path.
Thermal bridge analysis uses numerical modelling to investigate heat flow through a building-envelope junction. Depending on the project question, the analysis may examine thermal continuity, temperature distribution, internal surface temperatures, heat-flow paths and linear thermal transmittance through details such as slab edges, balconies, parapets, windows and façade connections.
Common locations include slab edges, balconies, parapets, window and door junctions, roof-to-wall connections, façade supports, steel framing and structural penetrations through insulation. Whether a particular junction is significant depends on its geometry, materials and the continuity of the thermal envelope.
A ψ-value, or psi-value, describes the additional heat flow associated with a linear thermal bridge and is typically expressed in watts per metre kelvin (W/m·K).
It can be used to quantify the thermal effect of junctions such as slab edges, parapets and window perimeters beyond the heat flow already associated with the adjoining building elements.
A lower ψ-value generally represents less additional heat flow through the linear junction for the calculation convention being used. However, the value should be interpreted within the relevant methodology and construction context rather than treated as a standalone design target. Surface temperatures, structural requirements, buildability, façade design and other project considerations may also be relevant.
Thermal modelling can calculate temperatures at internal surfaces around a junction under defined conditions. This can help identify locally colder surfaces and understand how the junction geometry, insulation and conductive connections influence temperature distribution.
A thermal bridge can create a colder internal surface, which may be relevant when condensation risk is being considered. However, a calculated surface temperature alone does not determine the wider moisture behaviour of an assembly.
Where the project question extends to surface or interstitial condensation, vapour movement, moisture accumulation or drying behaviour, a separate Moisture & Condensation Risk Analysis may be appropriate.
Two-dimensional modelling may be appropriate where a junction is effectively uniform along its length, while three-dimensional modelling can be required where heat flow is influenced by brackets, fixings, corners, penetrations or other geometry that cannot be represented adequately in two dimensions. The appropriate approach depends on the junction and the purpose of the analysis.
No. Detailed modelling may add little value where a junction is adequately understood through established construction guidance, suitable reference data or an applicable assessment method. Specialist analysis is more useful where the junction is unusual, geometrically complex, important to the project outcome or needs to be quantified more precisely.
Yes. Alternative insulation positions, thermal breaks, connection geometries and material arrangements can be modelled under consistent conditions. This allows the project team to understand how a specific change influences heat flow, surface temperatures or linear thermal transmittance before deciding whether the detail should be revised.
Typical information may include sections and junction drawings, dimensions, material build-ups, insulation locations, thermal-break information, structural connections and relevant material properties. It is also helpful to explain why the junction is being assessed and what decision the analysis needs to support.
Yes. Preliminary details can often be reviewed to determine whether a junction can already be modelled, what assumptions would be required and what information is still missing. Analysis during design development can also allow alternative details to be compared while changes remain practical.
Thermal bridging is considered within parts of the NCC building-fabric provisions, but this does not mean that specialist thermal bridge modelling is required for every project. The applicable requirements and calculation method depend on factors including the building class, construction and compliance pathway.
NatHERS includes methodology for representing thermal bridging associated with repeating steel-frame elements where insulation is interrupted. Specialist thermal bridge analysis can address different and more detailed junction-level questions, so the two should not be treated as interchangeable assessments.
Thermal bridge analysis investigates heat flow through specific construction junctions. Whole-building energy modelling considers the building at a broader scale and may assess heating and cooling demand, envelope performance, building services or energy use depending on the assessment method. Junction-level analysis may inform a wider assessment where relevant, but it does not replace it.
The scope depends on the number and complexity of the junctions, whether two-dimensional or three-dimensional modelling is appropriate, the number of design alternatives, the quality of the available construction information and the outputs or reporting required. A clearly defined junction and project question provide a stronger basis for programme and fee review.
The reporting scope depends on the project, but may include the modelled junction, material properties, calculation conditions and assumptions together with temperature distributions, heat-flow information, internal surface temperatures, ψ-values where required, comparison between design options and technical interpretation of the findings.
Thermal bridge analysis calculates the thermal behaviour of the construction detail represented in the model under defined conditions. It does not confirm that the completed junction will be constructed exactly as modelled.
Where verification of the completed construction is important, appropriate site inspection, construction quality assurance or other project-specific verification may still be required.
Related Knowledge
Thermal Bridge Analysis focuses on heat flow through specific building-envelope junctions. Related building physics services can investigate moisture behaviour, occupant thermal comfort and wider design-performance questions where the project extends beyond the thermal behaviour of an individual detail.
Moisture Behaviour
Investigate how building-envelope assemblies manage moisture, including condensation risk, vapour movement, moisture accumulation and drying behaviour. This extends beyond the heat flow and surface temperatures examined through thermal bridge analysis.
Explore Moisture & Condensation Risk Analysis →
Occupant Conditions
Assess how the combined indoor environment may be experienced by occupants across spaces and operating conditions. Thermal comfort modelling addresses broader occupied-space conditions rather than the thermal behaviour of an individual construction junction.
Explore Thermal Comfort Modelling →
Knowledge Gateway
Explore Certified Energy’s wider family of building physics, environmental modelling, solar access, shadow, visibility and spatial analysis services for Australian design and planning projects.
Explore Design & Planning Intelligence →
Project Review
Send the available section or construction detail, material build-up, insulation information and a brief explanation of what the project team needs to understand about the junction.
Certified Energy can review the available information and help establish whether detailed thermal bridge analysis is appropriate, which junctions warrant closer investigation and what additional project information may be required before modelling begins.
Where analysis is suitable, the scope can be structured around the project question and required outputs, whether that involves heat-flow investigation, internal surface temperatures, a ψ-value, comparison of alternative details or more complex two-dimensional or three-dimensional junction modelling.
Last reviewed: September 2026. This page is maintained by Certified Energy as part of its Design & Planning Intelligence knowledge ecosystem, within Building Physics.
