Tools for Greenhouse Gas Assessment Are Needed for District-Scale Planning

Urban planning often ignores emissions related to site preparation, which can account for 12% of a neighbourhood’s life-cycle emissions.

Greenhouse gas assessments at the level of individual buildings are an important step and are becoming common in many parts of the world. However, broader perspectives are also needed. Urban planning often completely ignores emissions related to the preparation of the building site (e.g., earth moving and soil stabilisation), infrastructure construction and maintenance, traffic, and soil and vegetation carbon sinks. Such omissions can lead to skewed perspectives on priorities in low-carbon urban development.
‍
The importance of accounting for these wider-area emissions is heightened by the insight that these are the very first emissions released during the life cycle of an urban project. For example, studies in Finland have shown that emissions from site preparation can account for up to 12 per cent of a neighbourhood’s total life-cycle emissions (Puurunen et al. 2021). In part to address this challenge, the city of Helsinki has adopted the newly developed AVA tool to assess emissions at a neighbourhood scale (see Box 6.2).

Figure 6.3 Greenhouse gas emissions per total floor area for 19 detailed plans assessed in Helsinki (50-year assessment period)

The construction and maintenance of buildings is by far the largest category of emissions.

Note: The assessed developments represent a wide variety of building uses and total floor area. Source: Puurunen et al. 2021.

Box 6.2

Finland’s “at-a-glance” AVA tool for greenhouse gas assessment at the neighbourhood level

Helsinki, Finland is using a neighbourhood-level greenhouse gas assessment tool called AVA, which can be applied to detailed plans covering one to five buildings, or urban blocks of apartments and/or office buildings. AVA was developed to be applied quickly and practically to typical urban plans, so that a planner can use it without expert understanding of greenhouse gas assessments. Despite the tool’s simplicity, its results have been shown to generally align with other methods (Tevajärvi 2022).
‍
Key goals in AVA’s development were to capture the main sources of emissions in buildings and infrastructure and to focus on issues that urban planners can influence, such as ideal material requirements for structures and foundations, the choice of concrete or timber for the structural frame, the level of energy efficiency, and a cap on the overall carbon footprint. This foreshadows an upcoming law that will make carbon footprint calculations required for all new buildings (Kuittinen, Ilomäki and Koskela 2021).

The speed and ease of use of AVA allow designers to compare the environmental impacts of different options for a site. Importantly, the tool can be applied to larger and more complex plans, although users need to be aware of the tool’s limitations as a ballpark assessment tool; on more complex infrastructure needs, assessments will need to be supplemented by more expert analysis.

Figure 6.3 shows results from AVA assessment of 19 different detailed plans in Helsinki, reflecting a diversity of built area sizes and building uses. In line with previous Finnish studies (Puurunen et al. 2021), the results indicate that three main activities dominate emissions: building construction, energy use and transport. In most cases, the construction and maintenance of buildings is by far the largest category of emissions. This shows a clear shift from older studies, which tend to show the dominance of operational energy in emissions. The contribution of buildings and construction to emissions is likely to grow, as scenarios indicate that both energy production and transport can be decarbonised relatively swiftly based on Helsinki’s targets and current actions.

The results in Figure 6.3 are revealing. For example, the impact of a timber frame is shown in case 18, which has the lowest emissions from building construction. Case 4 is located in a wooded area, which leads to a noticeable impact resulting from the loss of carbon sinks. In contrast, cases 12, 14 and 18 show developments where soil and vegetation carbon sinks were strengthened during the assessment period.

Climate pledges and decarbonisation pathways that ignore scope 3 emissions must be seen as inadequate.

Increasingly, cities are adopting municipal greenhouse gas assessments to account for local-level emissions. Under the Global Covenant of Mayors for Climate and Energy, more than 12,000 member cities estimate their annual emissions based on the Global Protocol for Community-Scale Greenhouse Gas Inventories (Global Covenant of Mayors 2016). Typically, city-level pathways to decarbonisation are based only on scope 1 emissions (emissions produced within the city limits) and scope 2 emissions (energy-related emissions) (Fong et al. 2021), with assessments for buildings based on the standard EN 15643. Scope 3 emissions, which include emissions that occur outside the city boundary as a result of activities taking place within the city, have received less attention (Linton, Clarke and Tozer 2022). These include the embodied emissions of building materials and other products used in cities but produced elsewhere.
‍
Climate pledges and decarbonisation pathways that ignore scope 3 emissions must be seen as inadequate. Consumption-based accounting of emissions is an absolute necessity as one basis for solving the climate crisis. For example, a recent comparison of greenhouse gas assessments in 10 European cities found that, in all cities, assessments of scope 1 and 2 emissions revealed significant reductions in emissions (up to 68 per cent) (Harris et al. 2020). However, assessments of scope 3 emissions showed that, in 8 of the 10 cities, consumption-based emissions were rising, by as much as 35 per cent. This highlights the important role of measuring and tackling embodied emissions.