Proposed Document Z – our proof of concept for implementing embodied carbon regulation

 

This proposed Building Regulations amendment ‘Part Z’ and Proposed Document Z outlines requirements on the assessment of whole life carbon emissions, and limiting of embodied carbon emissions, for all major building projects.

The proposal introduces mandatory assessments ahead of setting carbon limits, giving time to converge on robust yet ambitious targets.

Proposed Document Z is aligned with the Royal Institution of Chartered Surveyors (RICS) Professional Statement ‘Whole life carbon assessment for the built environment’, and guidance and recommendations made by the Royal Institute of British Architects (RIBA), the Institution of Structural Engineers (IStructE), the Chartered Institution of Building Services Engineers (CIBSE), the UK Green Building Council (UKGBC) and the London Energy Transformation Initiative (LETI).

If adopted, it would rapidly accelerate the voluntary action occurring across our industry, leading to green investment and green jobs creation across construction.

The need to introduce carbon regulation is supported by industry leaders, called for by the Climate Change Committee, and we hope that Part Z will be seen as an ‘easy win’ for the UK’s roadmap to Net Zero.

Reader notes to Page 1

This page summarises the format that the rest of the document follows, as well as highlighting key limits on application (size, and transition dates).

It reiterates what is said in the proposed Part Z regarding a minimum project size for which the document shall take effect. The 1000m2 limit shown here is a placeholder and is aligned with the proposed size limit in the Future Homes Standard.

It also shows staggered introduction dates between requirements Z1 and Z2, following the precedent set by other countries, and gives a period of time during which robust carbon limits can be determined. The proposed dates are shown as placeholders but follow the timescales followed by other countries.

Use classes are in accordance with those used on the Planning Portal.

[Square brackets] indicate key limits and dates. The proposed values must balance ambition with deliverability and should be determined through further consultation.

Reader notes to Page 2

The text given in the pink box on this page is a repeat of the proposed ‘Part Z’ to be inserted into Schedule 1 of the Building Regulations (2010).

It reiterates what is stated on Page 1 around size limits and transitional dates.

The page highlights the intention of Parts Z1 and Z2, namely that:

Part Z1 is intended to normalise the use of whole life assessments within the building design process, enabling design teams to identify ways in which to reduce the whole life carbon of the building. Assessment data will also be used to determine national targets for carbon in construction.

Part Z2 is intended to discourage excessive and unnecessary use of material within the built environment, by requiring a reasonable standard of efficiency of upfront embodied carbon.

Reader notes to Page 3

This page introduces the steps that must be taken in order to comply with Parts Z1 and Z2 of the building regulations. Note that the staggered introduction dates shown on Page 1 mean that some criteria will be statutory guidance rather than mandatory regulation when first introduced.

It is proposed that initially, Criterion 2 only limits upfront embodied carbon (modules A1-A5), enabling Building Control Officers to sign off compliance with Part Z by reviewing the final material quantities and environmental product declarations used in the building.

It is anticipated that this A1-A5 limit, in conjunction with the energy limits enforced by Part L, will enable the built environment to start to reduce the impact of its emissions – however the longer term ambition must be to extend the limits to include all whole life carbon modules that are reported (modules A-C, and module D). Data gathered as part of Criterion 1 would help this.

Reader notes to Page 4

The assessment of whole life carbon emissions is proposed to be undertaken with the RICS Professional Standard ‘Whole life carbon assessment for the built environment’ 2nd Edition, which is already the de facto guidance document on this topic in the UK.

This can be undertaken by any tool - paid, or free to use - provided that it is aligned with the RICS Professional Standard. For non-domestic buildings where Approved Document L requires an energy forecast in addition to the compliance model, (as defined by draft ADL-2 §5.18 and §9.4) then the energy forecast would be more suitable for this use.

Regarding the use of the word “builder” (e.g. clause 2.6), this is simply used for consistency with Approved Document L1A and others, and a wider design team involvement is expected.

Regarding the use of generic embodied carbon factors prior to starting construction (clause 2.6), this is in alignment with RICS, RIBA, CIBSE and IStructE methodologies.

Finally, note that a cross-industry team is currently developing a free-to-use Built Environment Carbon Database (BECD) that was launched in 2023 and should be used as part of this process to minimise cost and complexity to all.

The BECD includes a Product Database that will be reviewed regularly, and is therefore proposed to be referenced for the generic carbon factors required for clause 2.6. It also includes a Buildings Database that is proposed for use as the ‘government portal’ in clause 2.8.

Reader notes to Page 5

Table 1 as shown, which outlines the format in which whole life carbon should be reported, is based closely on the RICS Professional Standard, and will be aligned with the Built Environment Carbon Database (BECD).

Reader notes to Page 6

The final section of Proposed Document Z sets out the limits that would need to be achieved in future carbon assessments.

To start with, it is proposed that only upfront embodied carbon (modules A1-A5) is limited by regulation, enabling Building Control Officers to sign off compliance with Part Z by reviewing the final material quantities and environmental product declarations used in the building.

It is anticipated that this A1-A5 limit, in conjunction with the energy limits enforced by Part L, will enable the built environment to start to reduce the impact of its emissions – however the longer term ambition must be to extend the limits to include all life-cycle modules that are reported (modules A-C, and module D). Data gathered through the government portal / Built Environment Carbon Database (BECD) would help to enable this.

Reader notes to Page 7

Table 2 is shown as a placeholder for the carbon intensity limits that would be outlined in Proposed Document Z.

Prior to Part Z2 being mandated, guiding figures could be taken using the benchmarks provided in the Greater London Authority’s whole life-cycle carbon assessments guidance, available here. This would also align with targets work undertaken by RIBA, LETI, and the IStructE.

This highlights the benefit of utilising the free Built Environment Carbon Database (BECD) in order to capture construction data, allowing limits to be set at an appropriate level.

Part Z shown as an amendment to Building Regulations (2010) Schedule 1

The text shown here matches that shown with a pink background in Section 1 of Proposed Document Z.