Sustainability indicators proposed by the CEN for buildings and products

The International Standards Organization (ISO) defines a standard as: ‘a document, established by consensus, approved by a recognized body that provides for common and repeated use as rules, guidelines, or characteristics for activities or their results.’ The Technical Committee (TC) 350 of the CEN, named ‘Sustainability of Construction Works’, has developed voluntary horizontal standardised methods to assess the sustainability aspects of new and existing construction works, and for standards for the environmental declaration of construction products (table 2).

It is worth mentioning the existence of another standard published by the International Organisation for Standardisation, named ISO/TS 21929-1.2009 –Sustainability in the construction of buildings - Sustainability Indicators. Part 1: Framework

It is worth mentioning the existence of another standard published by the International Organisation for Standardisation, named ISO/TS 21929-1.2009 –Sustainability in the construction of buildings - Sustainability Indicators. Part 1: Framework to develop indicators for buildings.

All these standards identify the environmental indicators in Table 3 for the assessment of buildings. They reveal the importance of using a system of Sustainability Indicators for the sustainable certification of a project, for decision making, and for indicators to be internationally comparable. Even if this paper focuses on the assessment of buildings sustainability, it is of interest to note that the indicators suggested by the CENT/TC 350 for environmental product declarations are the same.

The World Commission on Environment and Development`s definition of sustainability (9) states that development must simultaneously consider the environmental, economic and social dimensions, which is a holistic and interdisciplinary approach (10), (11), (12), (13) suggested that environmental sustainable development objectives should be acknowledged and addressed in interventions designed to address social and economic priorities. (14) stated that the green building approach should consider three dimensions: environmental, social, and economical. Therefore, the assessments must take these three dimensions into account. In this way, a sustainable idea also expresses the interconnected nature of these three areas and leads to an economically feasible, socially viable and environmentally responsible project outcome (15), (16).

Within the social frame, Standard EN 15643-3:2012 establishes some generic categories of indicators completed with calculation methods. The intention of this Standard is for the assessment results to be compared between different countries by focusing on the social behaviour of both new buildings in their entire life cycle and existing buildings for their remaining useful life.

The social categories included to describe a building’s social behaviour are provided in Table 4.

Assessing social behaviour differs from economic or environmental assessments in that it requires an approach that is both quantitative and qualitative. When it is not possible to obtain quantitative results, checklists are typically used.

Within the economic frame, Standard EN 15643-4 : uses economic indicators to measure economic flows, such as investment, design, construction, making products, use, energy use, water use, waste, maintenance, deconstruction, developing the project’s economic value, the income made by the project and its services, etc. The economic indicators included to describe a building’s economic flows are shown in Table 5.

Next, the internationally recognised sustainability evaluation systems were selected, classified and cross-sectional studied by considering both effort-driven and data-driven assessments, and then checking if these indicators are included by data-driven and effort-driven methods, or not.

Data-driven sustainability assessment: the scientific method

Data-driven assessment tools are based on LCA, a methodology to assess the environmental impact of a given product or building throughout its lifespan. The term ‘life cycle’ refers to the notion that it must be holistic for a fair assessment; i.e. all phases need to be assessed, including raw material production, manufacture, distribution, use and disposal, as well as all the intervening transportation steps.

LCA procedures are described in ISO 14040:2006 and 14044:2006 as part of the ISO 14000 environmental management standards. According to ISO 14044, the main phases of a LCA are: Goal & Scope; Inventory Analysis; Impact Assessment; and Interpretation.

The first impact assessment step consists of drawing up an inventory list of all the input and output environmental flows of a product system. However, as a long list of substances is difficult to interpret, a further step is needed in impact assessments, known as a life cycle impact assessment (LCIA). An LCIA consists of 4 steps:

• Classification: all the substances are sorted into classes according to the effect that they have on the environment.
• Characterisation: all the substances are multiplied by a factor that reflects their relative contribution to an environmental impact.
• Normalisation (optional step): the quantified impact is compared to a certain reference value; e.g., the average environmental impact of a European citizen in 1 year.
• Weighting (optional step): different value choices are given to the impact categories to generate a single score.

According to this information, the impact categories can be used as indicators.

Effects on the environment considered by the different methods to conduct LCIA

For each substance, a schematic cause-effect chain needs to be developed that describes the environmental mechanism of the emitted substance. During this environmental mechanism, an impact category indicator result can be chosen at either the midpoint or the endpoint level.

Midpoints are considered to be links in the cause-effect chain of an impact category, prior to endpoints. Midpoint methods (CML 92, CML2001 version Baseline, EDIP 2003, EPD 2007, TRACI 2) are problem-oriented and translate impacts into environmental themes, such as ozone depletion, global warming and smog creation. Some methodologies (EPS 2000, Eco-indicador 95, Eco-indicador 99, IMPACT 2002+, IPCC 2001 GWP) have adopted characterisation factors at an endpoint level in the cause-effect chain. This is a damage-oriented approach that translates environmental impacts into issues of concern, such as human health in terms of disability adjusted life years for carcinogenicity or impacts in terms of changes in biodiversity (17). Endpoint results have a higher level of uncertainty compared to midpoint results, but are easier to understand by decision makers. Table 6 classifies the Endpoint-type impacts with the indicators considered by CEN/TC 350, and indicates which impact assessment methods (LCIA) evaluated them. Figure 1 shows the percentage of CEN suggested indicators considered in each LCIA tool.

As can be seen, tools with a higher proportion of CEN indicators implemented as Endpoint impacts are CML92 and CML2011, with the 40% of the environmental indicators (climate change, damage to ecosystem and damage to using resources) and the 8% of the social indicators (damage to health and emissions to the atmosphere, land and water). TRACI2 include the same but without the emissions to the atmosphere, land and water and use of secondary fuels. The other tools include even less than these do. None of them includes economic indicators.

Table 7 classifies the Midpoint-type impacts compared to the indicators considered by CEN/TC 350 by indicating which impact assessment methods (LCIA) evaluate them. Figure 2 depicts the percentage of CEN indicators considered in the Midpoint-type impacts.

Figure 2. Proportion of the indicators suggested by CEN considered as Midpoint type impacts in different LCIA tools.

Regarding the Midpoint level impacts, in general, LCIA tools applied a higher number of the CEN indicators. CML2 and EDIP 2003 are the most complete ones with the 45% of the environmental indicators and the 4% of the social ones. Only use of primary energy, use of materials, use of fuels and use of fresh water are not considered in EDIP2003. As can be seen in Table 7, some of the tools take into account the use of fuels and the use of metals and minerals although the overall number of indicators is lower than in EDIP. The only one social indicator considered in four LCIA tools is the emissions to the atmosphere, land and water. Again, economic indicators are not implemented in these tools.

Formulating indicators becomes a key element to assess sustainability. To this end, it is necessary to associate one impact or more with the indicator, which supplies a numerical value and its measurement unit (kWh/m2 year, kg CO2 eq./m2 year, l/person day). Indicators can derive from qualitative and quantitative measures, but they only become standardised and comparable when transformed numerically (18).

The sustainability indicators proposed in BSIS

Table 8 shows a list of LCA methodology-based tools developed in various organisations used exclusively to assess buildings or their components. These tools have been selected, because they can be used in the initial design phase, and allow the value of impacts to be obtained in real time by covering the different life cycle phases of buildings (19).