Skip to main content

Thermal Mass (Calculator) G#16163

By 18 November 2017December 5th, 2017Calculators, Encyclopaedia, Equations, Files

GBE > Encyclopaedia > Files > Calculators > G#16163

Thermal Mass Calculator

Thermal Mass Calculator

Free calculation tool for thermal mass (ISO 13786)

  • Finally I can provide the thermal-mass Excel-calculation tool, which I have promised for quite some time…
  • I hope this tool will help to get rid of all the simplified approaches suggested in the national standards and still used too much.
  • I don’t think that these simplified calculation methods should be applied any longer as they produce flawed results.
  • The precise thermal mass calculations involve multiplication of complex matrices, however this is no “rocket-science” and can be performed using standard excel spread-sheets.
  • I have therefore created a simple Excel-tool that does the maths for you.

Author: DI Daniel Rüdisser, HTflux

3 languages versions English German Austrian available here

If that link fails in future: Calculation tool Thermal Mass ISO 13786 Excel Calculator

Note: You are permitted and encouraged to use images from this page or to set a link to this page, provided that authorship is credited to “”.

GBE Comment

We cannot see inside the black box, buy the equations image indicate the inner workings.

But without a legend the equations are unfathomable to someone who was never taught this subject during Technician nor Architectural Education.

Thanks go to Daniel for doing this important work.

What is sad is that the cells to populate the calculator do not have look up tables to choose ready-made materials from, that then populate three of the next four columns.

In the absence of these look up tables we are all reliant upon having our own dataset to populate the cells manually with risk of error.

This tool currently remains a little unhelpful.

The words for materials choices ‘insulation’ in particular worries me a little since different insulation materials have widely varying characteristics in respect of decrement factor, specific heat capacity, thermal conductivity, etc.

Without a comprehensive set of materials in lookup tables we won’t be migrating away from cheap materials towards appropriate, competent, effective solutions very soon.

I have just searched around HTFlux website to see they have a comprehensive materials properties database that interacts with their calculator tools.

Time to subscribe?

Related article:
» Thermal transmittance and dynamic performance (thermal mass) of a timber-frame wall

Author: DI Daniel Rüdisser, HTflux

© GBE NGS ASWS BrianSpecMan aka Brian Murphy
18th November 2017

Thermal Mass Calculator


LinkedIn Building Physics Group

LinkedIn member Daniel Rudisser

Of HT flux

Has written and published a Thermal Mass Calculator in Excel for free use and distribution

The Equations go like this:


An explanation diagram goes like this:

© GBE NGS ASWS BrianSpecMan aka Brian Murphy
18th November 2017

Thermal Mass Calculator
See Also:

GBE Shop:

GBE Calculators

  • Loft Insulation U value and Raised deck support Psi Calculator
  • Whole Building EE EC SC (Calculator) G#1910 N#1764
  • Whole Building U value to In Use Carbon (Calculator)
  • WasteCost®Lite (Calculator) G#531 N#551
  • Elemental Assembly U value calculator

Other’s Stuff

Calculators By Others

GBE Issue paper

GBE Jargon Buster

Initials, Abbreviations, Acronyms:

  • AECB
  • C
  • CO2
  • CO2e
  • D&DT
  • EC
  • EE
  • PHPP
  • SAP
  • SBEM
  • SC
  • TSB
 Words or phrases:
  • Building Embodied Carbon
  • Building Embodied Energy
  • Building Energy Demand
  • Building Fuel demand and Carbon generated
  • Building U Value
  • CAPEM Compass
  • Carbon lite
  • Design & Decision Tools
  • Element area U Value
  • Elemental section U Value
  • Embodied Carbon (EC)
  • Embodied Energy (EE)
  • Embodied Water
  • Fuel Carbon
  • ICE Database (Jargon Buster) G#1018 N#1037
  • Innovate UK
  • Passivhaus
  • RetScreen
  • Sequestered Carbon (SC)
  • Shared Earth Building Embodied Carbon
  • WasteCost®Lite
  • Technology Strategy Board (TSB)
  • U value
  • WasteCost®Lite (by GBE)
  • Water Calculator (by AECB)

GBE Datasets

GBE Links

  • AECB
  • WRAP
  • CarbonLite
  • Innovate UK
  • Passivhaus
  • RetScreen

© GBE NGS ASWS BrianSpecMan aka Brian Murphy
18th November 2017



Leave a Reply