THERM — The Complete Guide: Free Thermal Bridge and Heat Transfer Analysis of Building Details
THERM is software from Lawrence Berkeley National Laboratory (LBNL) for 2D heat transfer analysis of building details. It is widely used in the window and building-envelope industry to compute frame U-factors and check thermal bridges.
THERM
Lawrence Berkeley National Laboratory
2D heat transfer analysis of envelope sections — thermal bridges, U-value and condensation checks.
Get it from the vendorWhat it is used for
- Window frames — U-factor of an aluminium or PVC profile, including a thermal break.
- Thermal bridges — wall-slab junctions, balconies, lintels and columns.
- Interior surface temperatures — checking condensation and mould risk.
- Materials — a library with thermal conductivities, and the option to add your own.
How to use it
Draw or import (DXF) the section, assign materials and interior and exterior boundary conditions, and the program meshes and solves. Results: isotherms, heat flux and U-factor. It works with WINDOW from the same lab to calculate the whole window.
What to know
THERM runs only on Windows, and downloading requires free registration. Calculations follow the American NFRC standards, but the method applies anywhere. For calculations to the European EN ISO 10211 standards in open source — Conducteo. For whole-building energy simulation — EnergyPlus.
WINDOW
Lawrence Berkeley National Laboratory
Thermal and optical properties of glazing systems — U-value, SHGC and visible transmittance.
Get it from the vendor
Conducteo
Clément Marcel (open-source project)
Linear thermal-bridge calculator to EN ISO 10211 — ψ-values and condensation risk for envelope details.
Get it from the vendorEnergyPlus
US Department of Energy
Annual building energy simulation — envelope, HVAC, thermal comfort and daylight. The US DOE engine.
Get it from the vendorOpenStudio
National Renewable Energy Laboratory
Graphical workflow on top of EnergyPlus — geometry, systems and scenario comparison.
Get it from the vendorThe bottom line
THERM is a professional, free tool for checking envelope details, especially useful for energy consultants, window designers and architects.