The carbon results presented in this calculator have been calculated using Slattery’s spend-based methodology for estimating upfront embodied carbon associated with building construction. The methodology converts total construction expenditure into an estimate of Scope 3 greenhouse gas emissions, expressed as kilograms of carbon dioxide equivalent (kg CO₂e). The results are derived from Slattery’s extensive cost and upfront embodied carbon database. The approach relies on data coverage and scale, rather than proprietary modelling assumptions.
The approach has been developed specifically for Australian building projects and is intended to provide a conservative, high level estimate suitable for corporate Scope 3 disclosure, internal reporting, and early-stage assurance where detailed material level data is not available.
The calculation applies a spend based emissions factor for every $1AUD of construction spend.
This factor represents an estimate of upfront embodied carbon and covers life cycle stages A1 to A5, including:
Demolition, operational emissions, and end of life stages are excluded from the boundary of this calculation.
The spend based factor is designed to be conservative. It is based on the upper range of emissions intensity observed within the underlying dataset and is intended to avoid underestimation where project specific carbon data is unavailable. Where low carbon materials, recycled products, or adaptive reuse strategies are employed, actual emissions may be materially lower than the estimate produced by this method.
This methodology is not a substitute for first principles measurement or detailed material take off based carbon assessment.
The emissions factor has been derived from a proprietary dataset of Australian building projects held within Slattery’s cost and carbon planning database.
The dataset is unique in that it includes projects where the following were provided by Slattery:
This enables direct comparison between total upfront embodied carbon outcomes and total project expenditure on a like for like basis.
Embodied carbon calculations within the dataset are informed by the following sources and assumptions:
Cost data reflects total project costs at tender and includes all project phases, consultant fees, furniture and equipment allowances, contingencies, authority and statutory charges, and escalation allowances applied up to tender. Costs are expressed in tender-stage dollars and exclude post-tender cost escalation.
The dataset and resulting factor apply to building projects only. Infrastructure, civil, and horizontal works are excluded due to materially different cost structures and emissions profiles.
Projects included in the dataset generally reflect proactive client teams that engaged in carbon planning services. While this may indicate a bias toward lower embodied carbon outcomes, the final factor remains conservative as it is derived from the highest emissions intensity values observed within the dataset.
Despite this conservative approach, Slattery’s spend-based carbon factor remains lower than the current Climate Active spend-based equivalency figures. This reflects the use of more recent, project-specific cost and embodied carbon data derived from real construction outcomes, rather than higher-level national averages.
The Carbon Index is updated regularly and date-stamped. As lower-carbon materials, construction practices, and supply chains become businesa-as-usual, these changes are progressively reflected in the dataset and associated spend-based factors.
This methodology provides a practical and credible baseline for:
Users seeking higher accuracy or project level emissions reduction strategies should undertake a detailed embodied carbon assessment.
