Full-life Cradle-to-Grave calculation

Ben Adam Smith

Embodied CO2 is often a larger part of the total footprint of a Passivhaus because operational CO2 is substantially lower. Moreover, it is also becoming more important as the grid decarbonises. Domestic heating is mostly using natural gas in this country, and that also has a target to be decarbonised as well, 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.

Materials from your PHPP are matched to the list of materials automatically so you only need adjust the choice where necessary. It remembers associations you make between phrases in the PHPP and materials. You can also choose whether you want to see products manufactured within your country, a region e.g. Europe, or all the EPDs.  You make the choice just once but you can broaden the range temporarily if you can’t see the material you need.

  • typical house calculation a few minutes +look up special materials + checking
  • uses standard RICS methodology including 60 year nominal life
  • uses data from 200 material entries from EPDs and a further 100 from summaries of EPDs
  • matches materials automatically, though user needs to confirm each
  • fully referenced with links to the EPD and the source of the density and product life
  • user can adjust the density of some products, standard densities are offered
  • stored carbon for timber based products is included, easy to turn off for all, or for non FSC/PEFC
  • easy choice of units for the y axis of graphs
  • plenty of space provided for you to add in comparison constructions
  • writes a form below the calculation for you to keep a record of exactly what is included
  • data entry for Embodied CO2 being developed for you to enter your own EPDs

PHribbon now calculates Embodied CO2 from Cradle to Grave, covering stages A-C (and D where information is available) and is suitable for initial estimates for the RIBA 2030 Challenge.  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
Stage D, Reuse, Recycling potential (outside the usual scope of the calculation)

Three examples of built projects modelled with PHribbon embodied CO2 are shown below. The left hand one also includes a comparison between the house as built and what it would have been using typical cavity wall of the same U-value.

You can buy the tool and do the calculation yourself, or Tim Martel also offers to do the calculation for you, his website is www.optimalretrofit.co.uk
Technical details of the tool are available PHribbon -Tool Information Sheet.

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 Passivehaus+ 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”.