Building envelope heat transfer

KOALAflx

KOALA calculates two- and three-dimensional steady-state heat transfer in building envelope assemblies. The standalone editor and Rhino plugin support building science research and teaching, architectural detailing, and engineering assessment.

Download the app Rhino plugin installation
KOALA standalone app: steel stud wall with its temperature field KOALA standalone app: steel stud wall with its temperature field
KOALA app · 2D analysis of layered constructions
KOALA for Rhino: temperature slice through two balconies, one with a thermal break, in the Rhino viewport KOALA for Rhino: temperature slice through two balconies, one with a thermal break, in the Rhino viewport
KOALA for Rhino · 3D analysis of Rhino geometry
ISO 10211 validation All four Annex C reference cases, 2D and 3D Graded mesh Material interfaces resolved with graded cell spacing Numerical methods Sparse Cholesky and conjugate gradient solvers Public beta Windows, macOS and Rhino 8
KOALA app · Windows & macOS

Thermal analysis of layered constructions

Define homogeneous layers, timber or steel studs, profiles and partially filled cavities in a construction table. The two-dimensional calculation resolves heat flow through the layer arrangement and framing, with results for comparison to the simplified estimate.

  • Calculated U-value including thermal bridging, with a parallel-path estimate for comparison
  • Temperature and heat flux fields, with steady-state vapour diffusion screening
  • ISO 13786 dynamic properties: decrement factor, time shift, admittance
  • EnergyPlus IDF export of an equivalent construction matched to the calculated U-value
Read the standalone guide
Timber frame wall analysed in the KOALA app Timber frame wall analysed in the KOALA app
KOALA for Rhino · Rhino 8

Three-dimensional junction analysis in Rhino

Assign materials and indoor and outdoor boundary conditions to Rhino layers. KOALA discretises the assigned geometry on a graded grid to calculate heat transfer through balconies, brackets, window installations and other junctions. Layer priority determines material assignment where volumes overlap.

  • Temperature, heat flux and relative humidity fields displayed as viewport slices
  • Linear (Ψ) and point (χ) thermal bridges, plus Uf, Ψg, installation Ψ and Uw
  • Clear-field layer tracing and EnergyPlus export matched to the calculated U-value
  • Export slices and result points as Rhino geometry for use in Rhino and Grasshopper
Read the Rhino guide Download the balcony example (.3dm)
Balcony with and without a thermal break: 3D temperature slice in Rhino Balcony with and without a thermal break: 3D temperature slice in Rhino
Windows · frames · installation details

Window frame, glazing-edge and installation assessment

The Library provides window-in-wall examples and glazing units with or without frames. Window Analysis defines the reference widths and projected outer-frame area used by each assessment. Measurements can be entered or drawn in Rhino and reviewed alongside a labelled diagram.

  • Frame Uf, glazing-edge Ψg and installation Ψ for section details
  • Whole-window Uw from the projected outer-frame area
  • Uf and Ψg assessment of a user-modelled frame around an IGU
  • Reference measurements saved with the Rhino document and included in the shared report
Window analysis workflow
Window Analysis: reference measurements, coloured diagram and assessment controls Window Analysis: reference measurements, coloured diagram and assessment controls
Reference measurements, assessment requirements and calculation controls.
Rhino workflow

Rhino analysis procedure

  1. Model on layersOne Rhino layer per material, plus volumes for the indoor and outdoor air.
  2. Assign materialsPick from the library, or double-click to edit assigned properties. Layer order sets priority.
  3. SimulateAuto cell size, optional mesh check, cancellable progress.
  4. Read the resultsSlices, Ψ/χ, IDF, baked geometry and report images.
Calculation methods

Analysis outputs

Temperature field of a steel stud wall Temperature field of a steel stud wall

Temperature fields

Review temperature fields, isotherms and surface temperatures at framing, profiles and connections.

Heat flux through a framed wall Heat flux through a framed wall

Heat flux

Examine heat flux distributions and the contribution of framing to overall thermal transmittance.

Relative humidity in a timber frame wall Relative humidity in a timber frame wall

Condensation risk

Steady-state vapour diffusion screening (Glaser method) identifies calculated condensation conditions.

ISO 10211 case 3 temperature section

3D thermal bridges

Projecting slabs, corners and point bridges solved in 3D, with Ψ and χ values.

Equivalent U-value and IDF export

EnergyPlus export

Export an equivalent layered construction with the modelled thicknesses and mass, matched to the calculated U-value.

Dynamic analysis

Dynamic properties

ISO 13786 decrement factor, time shift and admittance for summer comfort and thermal mass.

Numerical verification

ISO 10211 reference cases

The tables report results from automated solver tests. For the projecting-slab reference case, the reported heat-flow difference is below 0.15 % at the default cell size.

ISO 10211 reference caseSolverResult
Case 1: half square column2D✓ Complies with ISO 10211
Case 1: half square column3D✓ Complies with ISO 10211
Case 2: frame with thin aluminium2D✓ Complies with ISO 10211
Case 2: frame with thin aluminium3D✓ Complies with ISO 10211
Case 3: rooms in a wall corner with a projecting slab3D✓ Complies with ISO 10211
Case 4: iron bar through insulation3D✓ Complies with ISO 10211

All results and figures

Download KOALA for your platform

Public Beta (Expires January 1, 2027)

Windows

v1.0.0 (x64) Download .exe

macOS

v1.0.0 (Universal) Download .dmg
Rhino 3D

Rhino 3D

Plugin (v1.0.0) Package Manager