Ben Adam Smith

Domestic heating is mostly using natural gas in this country, though that is changing, you may have heard that after 2025 gas boilers won’t be available.  The largest part of what remains after these head towards zero is the embodied CO2 of the construction.  Tim goes into more depth in a recent podcast (2020) podcast 283 with Ben Adam Smith of House Planning Help.

There is a standard for Embodied CO2 calculations in the UK, the RICS Professional Statement on Whole Life Carbon. This is based on EN 15978 and it is used by RIBA, CIBSE and IStructE. In December 2020 the UK Government required that central government should adopt the use of whole life carbon assessments for all public works projects and programmes, including building, civil engineering, construction and equipment projects in their “Construction Playbook”, read more in this article.

What it does

PHribbon calculates Whole Life Carbon, that is Embodied CO2 from Cradle to Grave, covering stages A-C (and D where information is available). It is suitable for initial estimates for the RIBA 2030 Challenge v2 and LETI. This therefore includes :
Stage A, A1-A3 Manufacture including A4 Transport to site and A5 Construction
Stage B, Use of the building including B4 Replacement
Stage C, Demolition and Disposal of the building
And quoted separately Stage D, Reuse, Recycling potential (outside the usual scope of the main calculation). It calculates the credit from reuse of an element, assembled part such as a frame, or something that is reused offsite.

There are 2 UK versions of the AECB Embodied CO2 calculator, they look very similar and have exactly the same calculation. One is part of the PHribbon tools and links in with PHPP, the Passivhaus Planning Package, for those who use that. The other is a stand-alone calculator that works independently – this looks very similar, it just doesn’t produce the combined Embodied and Operation graph. The PHribbon version is has been available for a few years in earlier forms but now has been updated for more detailed end of life calculations.

Input Data

  • built-in library of 291 entries from EPDs containing the Full Life info for stages A-D and a further 140 from ICE 2019 with manufacturing data (A1-A3)
  • includes CO2 stored in timber and timber based materials, also called sequestered CO2. This is calculated where it has been omitted in the EPD.
  • standard RICS methodology including 60 year nominal life
  • filters EPDs, choose whether you want to see products manufactured within your country, a region e.g. Europe, or all the EPDs
  • [PHribbon version only] matches materials automatically,  you only need adjust the choice where necessary, you can now also see both the original material and the material it was matched with, in case there is a difference
  • [PHribbon version only] remembers associations you make between phrases in the PHPP and materials


  • coloured results, the output table is coloured by value to make it easy to see where the CO2 is coming from
  • fully transparent calculation
  • up to 4 options can be graphed/compared
  • simpler format and option to simplify further so only the names of the materials and results are shown
  • density, you can change the density of products where units are “kg” in the final output sheet (you can also change any in PHribbon’s library)
  • Scope Summary written below the calculation for you to keep a record of exactly what is included
  • RIBA results gives RIBA 2030 Challenge results and [PHribbon version only] gives data in the format for RIBA awards applications
  • [PHribbon version only] Total CO2 graph shows operational and embodied CO2 over 60 years (Button also to extend this >60 years)
  • [PHribbon version only] AECB Assessment summary that is printable
  • LETI results graphic and detailed tables, all laid out on printable pages

Results are also given by each stage for each material. The automatic colouring makes it easy to spot what material is contributing most and at what stage:

The graph below left shows the Embodied CO2 of up to 4 options.  Below right is the combined Embodied and Operational CO2 using the data calculated in PHPP.  (Graphs normally show a maximum of 4 options, here the one on the right has been manually customised to show 5).

RIBA and LETI results are shown in the LETI format and allow for slight measurement differences:

Recent Updates

  • End of Life calculations: Since version 4.0 PHribbon has updated the End of Life calculations so that it can use the calculations in an EPD which match the mix of recycling/incineration/landfill defined for the UK (or your country if you change it). It can also use “100% scenarios” in the EPD, allowing any combination to be chosen. If neither of these are available then the RICS estimates are used.
  • RIBA, the Royal Institute of British Architects results are now given, using the updated RIBA 2030 challenge v2 figures.
  • LETI, the London Energy Transformation Initiative results also given with the LETI graphic (in ver 4.07). RIBA and LETI have slightly different assumptions in their calculations meaning that occasionally the RIBA result will not match the LETI one.
  • Landfill methane capture can be included, UK landfill sites are required to capture methane and even though this results in the methane being burnt, releasing CO2, the emissions are slightly lower than that for releasing methane into the atmosphere.
  • Refrigerant leakage calc built into the heat pump selection, allowing you to choose the type and size of system, and the type of refrigerant. (in ver 4.07)
  • Module D reuse credits included. There is now a simple way to include the credits from reuse of materials on site as elements, an entire structural frame, or offsite (in ver 4.07)
  • Layout of main table simplified so that only essential items have to be shown, others can be hidden to one side. All the data entry cells are together, making it simpler to follow (in ver 4.07)
  • Guidance, error messages and checks to alert you to things you have missed.

Published work

Some of our recent calculations have been published in Passivhaus+ magazine (links are valid for subscribers and to others while Passivhaus+ is offering free access)

  • Steep Wedge House (new build) – issue 31 p49
  • PYC Offices (new build) – issue 32 p23
  • Greenheart Construction (new build) – issue 33 p29
  • Ruth Butler (new build) – issue 33 p38
  • and Passivhaus+ is keen to include these for regular feature of the projects they show issue 33 p18.

Results from the tool matched (within the error margins) Mark Siddall‘s own 2-3 day calculation. The Embodied tool was in development when Mark did his calculation and he was interested in a to see what it would produce, before revealing his own results. When it gave the same answer in about half an hour he said “I’ll definitely be using it next time”.

Sales of both UK versions are soon moving to the AECB shop. Training will be online with live sessions when minimum numbers are met. US and Canadian versions will be sold through NAPHN and Passive House Canada, we estimate in mid September.