The Delivering Net Zero in Use Toolkit has been developed to complement 'Delivering Net Zero in Use: a guide for architects', which was first published in November 2022 as part of AHMMs Knowledge Transfer Partnership with UCLs Institute for Environmental Design and Engineering. 

The toolkit was developed in response to a need to coordinate and visualise a projects carbon data across all stages and disciplines of a building project. Users can input predicted carbon data from multiple consultants into the Excel based programme, which can generate two graphic outputs: an interactive waterfall diagram which shows carbon emissions, and a carbon square which ranks carbon alongside time, cost, and quality drivers. The Toolkit can also identify where missing data is required and set targets for the gaps based on best practices. 

It was initially designed to be used for our own large, complex, mixed-use developments, which often have multiple variables, changing stakeholders over a long period of time, and tenant changes, to measure the collective impact of these factors on embodied and operational carbon.

The tool has now been developed as an open-source tool that can be used for buildings of different typologies, and it enables the entire client and consultant team to look at information, collectively understand the impact of the individual disciplines and develop realistic targets together. 

Processing the data in this way allows teams to have a holistic view of a project's cradle-to-cradle carbon impact, and, importantly, provides the opportunity to assess how iterative changes to a building's design, delivery, operation, and demolition, can optimise its environmental impact. The tool can be used to take into consideration the environmental impact of CAT A and interior fit-out removals associated with lease changes in commercial and mixed-use developments. 

Download the Toolkit here. To start using the Toolkit, click File > Save As, to download an editable version onto your computer. 



A navigation worksheet is provided to allow the user access to the various worksheets and diagrams of the Toolkit. Clicking the navigation button takes the user to the input tabs, where data can be entered for the net zero carbon diagrams and carbon square. The navigation tab outlines the sequential steps necessary to complete the whole life carbon and carbon square tools.

The Toolkit has been developed to support several levels of engagement. A simplified tool allows for the input of high level targets, project aspirations or data of a basic nature. More detailed information can be entered by clicking on the + symbol to open up rows and columns which provide opportunities for additional data input.

The Net Zero In Use Toolkit is based on a framework where sustainability reviews are undertaken at key stages of a project. These reviews are typically aligned with the RIBA Plan of Work but in recognition of the needs of a project this can change (for example, two reviews might take place at Stage 2 or 3 in response to specific project requirements).


The navigation tab of the toolkit provides navigable links across the spreadsheet. 

There are seven steps which include inputting details about the project and its embodied and operational emissions, along with any proposed mitigation measures.

At stage eight a simplified or detailed net zero diagram will be produced based on the data that has been entered. There is an additional option of producing a carbon budget diagram if a top-down science-based target approach has been adopted.


This part of the spreadsheet is used to track the progress of a project against the net zero carbon benchmarks such as the RIBA 2030 Challenge or LETI benchmarks as part of the AHMM sustainability toolkit process.

Worksheet one is for project information:

(1) Project Data
The date of practical completion, construction start date, and GIA should be provided here. By providing a benchmarking typology, the project's targets can be understood in relation to these frameworks. Other information about the project such as floor-to-floor heights can be entered on this worksheet.


Worksheets two to five are for charting emissions data input:

(2) Module A1-A5 - Embodied
The Upfront Embodied Carbon worksheet allows the user to provide a high level target or detailed breakdown of embodied carbon based on the RICS categories.

(3) Lifecycle B2, B3, B4 & B5
It is recognised that identifying lifecycle embodied carbon can be challenging. Understanding lifecycle carbon requires a designer to understand when key components will be replaced. To support the user the Toolkit can provide a proposed breakdown of lifecycle carbon based on RICS replacement rates, an assumed component percentage split and targets from the project data.

(4) Operational B1, B6 & B7
The project EUI should be entered on this worksheet. The EUI and practical completion date (entered on the project data worksheet) is combined with grid decarbonisation data to provide carbon emissions.

(5) Module C - End of Life
This worksheet is for emissions associated with demolishing the building. Based on LETI guidance a proposal of 2% WLC target can be allocated for these emissions.


Worksheets six to seven are for data input or mitigation measures:

(6) Module D Reuse
Proposed savings associated with the reuse building components can be entered in this worksheet. Currently there are few guidelines about carbon savings from the reuse of building components at the end of a building's life.

(7) Mitigation
Unlike the other worksheets this worksheet offers a binary set of yes and no options relating to the approach of offsetting proposed by the project team, as opposed to a quantitative input. This approach means that offsets are allocated based on current net zero frameworks (i.e operational emissions compensated by the purchase of off-site renewables or upfront embodied carbon by other offsetting approaches).


The net zero carbon diagram is a visual representation of all the data entered into the Toolkit.

There are two versions of this diagram: (1) a simplified diagram based on high-level targets or analysis; and (2) a detailed diagram based on more extensive information.

On the vertical axis is both RICS module and life cycle carbon. The horizontal axis is time, pinned to the notional 60 year design life span of a building.

By experimenting with different design ideas for upfront, in use and operational aspects of a project, this visualisation will help to interrogate different options for a building.


The carbon square tool within the Toolkit supports teams who wish to interrogate perceptions of the fundamental drivers of a design. This tool has been incorporated into the framework to inform and assess decisions in relation to carbon over the course of the project.

It is anticipated that a review of project drivers using the carbon square tool can be undertaken at key workstages. The tool facilitates one-to-one interviews with several participants; however, it is hoped that this review will be undertaken in a workshop format. The benefit of a workshop format is that it can support an open discussion about the place of carbon alongside other project drivers. To support an assessment of project drivers, the tool provides a capacity for the consistency if responses to be interrogated.

The carbon square can be accessed through the navigation tab which takes the user to the carbon square diagram and interview sheets.


Delivering a net zero carbon building requires an integrated design process where specialisms have to work closely together to deliver holistic solutions. One part of applying an integrated design solutions to the delivery of net zero carbon buildings is for the designers to have a good understanding of whole life carbon emissions at every stage of the project.

The carbon square tool can be used as the basis of a charrette or workshop to investigate the vision, goals, and desired outcomes of a project and also understand any contradictions in relation to project drivers.

At early stages the Toolkit supports understanding of project targets in relation to national and local benchmarks. The carbon diagram Toolkit can be used to provide insights into the status of the design in relation to the project's net zero aspirations.

As the design develops and a more comprehensive picture of the building carbon emissions is developed the Toolkit can also be used to explore different approaches.


To start using the Toolkit, click File > Save As, to download an editable version onto your computer.