Chapter 6
Measurement and Data Are Improving, But Transparency and Verification Are Needed 
Existing Tools for Assessing Carbon Impact
Recommendations for Future Carbon Assessment Tools
Tools for Greenhouse Gas Assessment Are Needed for District-Scale Planning
Global Standards and Labels for Emission Transparency Can Galvanize the Market
Challenges and Next Steps

Table 6.1

Tools and standards used to assess life-cycle emissions

Life-Cycle Assessment

Life-cycle assessment refers to a systematic analysis and evaluation of the potential environmental impacts of material products or services during their entire life cycle, from production to distribution, operation and end-of-life (or use) phases. In 2006, the International Organisation for Standardisation (ISO) issued two revised standards for life-cycle assessment – ISO 14040 and 14044 – that set out a four-stage assessment process: 1) goal definition and scoping (ideally including all direct and indirect sources of emissions throughout the life cycle), 2) life-cycle inventory (collecting data on all the system inflows and outflows), 3) impact assessment (classifying these flows into environmental impact categories and characterising them by their impact potential) and 4) interpretation (ISO 2006a; ISO 2006b).

GHG Protocol

The Greenhouse Gas (GHG) Protocol, founded in 1997, aims to establish a set of clear, rigorous and consistent accounting rules to calculate the “carbon footprint” of products. The initiative introduced a three-fold categorisation of life-cycle greenhouse gas emissions: scope 1 (direct emissions from own facilities and vehicles), scope 2 (indirect emissions from purchased electricity and fuels) and scope 3 (emissions from all other upstream and downstream activities). Of special interest to the built environment sector are software tools that help calculate the greenhouse gas emissions of specific sub-sectors and materials, including aluminium, cement, iron and steel, and wood. Importantly, the GHG Protocol also includes several complementary standards for the calculation and management of emissions at different scales, from products to the corporate level to whole cities.

Environmental Product Declarations

Environmental product declarations are one of three types of environmental labels established under ISO 14020 standards for ecological labelling, designed to help businesses measure and communicate their efforts to minimise their environmental impact (ISO 2006c; ISO 2016; ISO 2018; ISO 2022b). Of the three label categories – certified eco-labels, product self-declarations and environmental product declarations – only the latter mandates the use of life-cycle assessment to quantitatively estimate life-cycle impacts, including greenhouse gas emissions. In 2012, the European Committee for Standardization (CEN) published standard EN 15804 to regulate how life-cycle assessments are applied to environmental product declarations in the construction sector (CEN 2019). However, concerns remain among stakeholders regarding the limited transparency and access to development processes for environmental product declarations (Gelowitz and McArthur 2016).

Product Environmental Footprint (PEF) and Organisation Environmental Footprint (OEF)

Since 2012, the European Commission has been developing an ambitious scheme aimed at providing detailed guidance for calculating the “environmental footprint” of a product and organisation (European Commission Joint Research Centre n.d.). While based on life-cycle assessment, these efforts aim to improve consistency and comparability by mandating specific choices in terms of system boundary, allocation procedures, impact assessment methods, etc. One notable innovation is the use of a “circular footprint formula” to enable the consistent calculation of end-of-life recycling credits across all life-cycle assessments that are compliant with the PEF.* Development of the PEF methodology is still in progress, but it has already resulted in at least one mandatory standard: the 2019 revision of EN 16804+A2 for the European construction sector (CEN 2019) with a more rigorous accounting of biogenic carbon flows.

*A detailed discussion of the methodological implications of this formula is beyond the scope of this report, but it is essentially a case of establishing an agreed-upon compromise rather than correcting or improving upon the previously existing alternative methodological options.

Existing Tools for Assessing
Carbon Impact

Decision-makers need easier access to the right data to assess the carbon impacts of their material choices.

For decision-makers to adopt and apply whole life-cycle thinking and make optimal decisions about decarbonisation, they must have access to the right data to assess the carbon impacts of their material choices. Rigorous estimation of the “carbon impact” of building materials across the building life cycle is not an easy or trivial task, and in the past significant expertise and time were required to make proper life-cycle assessments (Takano et al. 2014).

Current efforts are improving the accessibility of this task through the use of “at a glance” tools. Analysts now have key tools to draw from, developed during three decades of methodological refinement, as well as a series of detailed and pragmatic sector-specific standards and guidelines. These tools attempt to solve the problem of producing consistent results that can be meaningfully compared across studies. However, further development is required to address variability in data provenance and reliability. Table 6.1 provides a summary of some of the most common tools for assessing life-cycle emissions.