Net Zero Carbon Assessments

08 June 2021

Ridge and Partners are able to undertake a Net Zero Carbon Construction (NZC) assessment on new build and refurbishment developments.

The purpose of a NZC Assessment is to develop a pathway to a NZC footprint. ‘Net Zero Carbon’ is the achievement of effectively delivering zero emissions from the development, through residual reduction of embodied carbon and offsetting of the remaining carbon emissions. The study is limited to the embodied carbon of the development currently, with operational energy currently considered as a separate study.

UK Green Building Council (UKGBC) – Scope
The NZC assessments are carried out in line with the Net Zero Carbon in Construction scope contained within the UKGBC Net Zero Carbon guidance document (UKGBC Framework Definition, April 2019). This definition scope equates to the embodied carbon emissions associated with the production of all building materials / products, and impacts associated with transportation to site and construction. The construction scope aligns with modules A1-A5 as set out in EN15978 and covers the carbon emissions up to the point of practical completion.

In a standard assessment the design team are also required to demonstrate how the development has been designed to reduce energy demand and consumption, and increase on-site renewable energy (e.g., facilitating future installation of renewable technologies, specifying low energy consuming systems, reducing energy demand through passive measures). This design work facilitates any future declarations on operational energy carbon emissions.

The carbon emissions at practical completion are then offset via a UKGBC approved offsetting mechanism, and the summary of the NZC assessment and offsetting are publicly disclosed, allowing the development to be declared as Net Zero Carbon in Construction.

UKGBC – Offsets

As recommended in the current UKGBC offsetting guidance, the embodied carbon offsetting process can be achieved via a one-off payment of offsets made at the point of completion, to compensate for the total carbon emissions calculated.

UKGBC guidance advises that carbon offsets can be procured via existing offsetting standards that have clear and transparent governance, encapsulated by having requirements and procedures for ensuring the environmental integrity of the carbon credits. The UKGBC guidance highlights that The International Carbon Reduction & Offsets Alliance (ICROA) provides a list of permitted carbon offset standards, which include but are not limited to –

– Gold Standard – (
– Verified Carbon Standard (Verra / VCS) – (
– United Nations Clean Development Mechanism (CDM) – (
– UK Woodland Carbon Code (

Gold Standard, UN CDM and the VCS frameworks all facilitate the purchase of carbon credits (also known as certified emission reductions / CER’s under the CDM and verified carbon units / VCU’s in VCS). These credits support development projects which ensure a reduction in carbon emissions, amongst other benefits, e.g., the installation of photovoltaic arrays, reforestation efforts or improvement of cook stoves.

The price associated with each tonne of carbon varies between the different frameworks and different projects and the quantity of credits available to purchase on a project-by-project basis also varies. Gold Standard, UN CDM and VCS are all global schemes, with most projects located in developing countries.

The UK Woodland Carbon Code is the most recent addition to the UKGBC guidance and allows the purchase of Woodland Carbon Units (WCU’s) which are a tonne of CO2 sequestered in a WCC-verified woodland. This framework also allows purchase of Pending Issuance Units (PIU’s), which are effectively a ‘promise to deliver’ a WCU in future, based on predicted sequestration of carbon. PIU’s cannot be used for offsetting currently as per UKGBC guidance, and the number of WCU’s currently available for purchase stands at around 800 tonnes, so in the near future the UK Woodland Carbon Code does not offer a standalone route to offsetting development projects of this scale.

UKGBC advise that offsets should be purchased at RIBA Stage 6, however in subsequent discussions it has been accepted that offsets can be secured prior to this point. The offsets need to be sufficient to cover the total reported at RIBA Stage 6, so a partial purchase approach could be pursued to secure part of the offsets early.

Assessment Process

Ridge utilise Life Cycle Assessment (LCA) software which allows for the modelling of a building’s embodied carbon impacts, using underlying datasets which comply with the UKGBC requirements.

The embodied carbon emissions of the buildings are calculated through the collation of information on material choices and quantities for the building elements, with construction site impacts including transport and site equipment also factored in.

A RIBA Stage 3 model is developed initially, using estimated quantities / material choices from the tender design, following which an early indication can be provided for the anticipated carbon impact and subsequently allow consideration of possible offset costs.

Once the initial results are reported, guidance will be provided on the carbon hotspots in the scheme, to allow the team to consider carbon reduction measures.

The model will then be updated using actual quantities and material choices during the early construction phase (RIBA Stage 4 / 5) based on Contractor input and implementing any agreed carbon reduction measures. This model is then revisited and updated at handover (RIBA Stage 6), utilising as built quantities and material choices.

During the modelling, Ridge will provide a third-party review of the information provided by the project team to ensure the model is robust and accurate in its inputs and assumptions. The LCA software providers will also provide a modelling check to reinforce the model’s accuracy.

This final, as built model then allows the appropriate quantity of offsets to be purchased and a declaration to be made for the development via public disclosure. The development can then be labelled as Net Zero Carbon in Construction.

Contact a member of our team to find out more:

Wendy Broomhead

Nick Hayes

Abby Bartlett