The case-study of this research aimed to fill in the gaps in the current knowledge, as identified in the literature review. It looked into the depletion of natural raw materials, through an assessment of lifetime abiotic depletion potential (ADP) of a residential multi-storey case-building with concrete structures, for both ADP elements and ADP fossil, as defined in current guidelines [24
]. It should be highlighted that due to the case-study approach, the generalization of the results should be done with caution, especially considering the building type and location.
The material quantities were extracted from the building information model (BIM) of a real world building, so the data accuracy for initial material consumption can be considered high. The material losses, on the other hand, were estimated to be at the level of 5% of total material consumption. Commonly used values in literature vary from 0% to 10% [70
]. Also, the lifetime material needs for replacements and refurbishments were assessed through simple estimates on service lives of different building components. An analysis on the impacts of estimation errors show that a change of 25% in these factors would increase/decrease the material amounts by some 10% for the case-building.
The case-study used the European reference life cycle database, ELCD [71
] to derive the abiotic material inputs and energy requirements for each of the main materials of the building. The LCIs of the database are compiled mainly by process analysis. It can be argued that this method is associated with underestimation of the impacts, as the number of processes and the order of upstream processes are limited [68
], and sufficient boundaries may be difficult to cover due to the complexity of upstream processes [69
]. For basic building materials, for example, the incompleteness factor, often referred to as truncation error [66
] is estimated to be at least 10% [69
], some estimates being as high as 60% for residential buildings [67
It should be noted that the data sources for the ELCD-database are drawn on a wider regional level and the energy inputs for the production processes use country-level statistics and national grid-mix information and they are not pure process based analyses. This enhancement of process-based information with IO-based data can be considered to make the profiles of ELCD profiles hybrid analyses in a sense [69
The ADP characterization factors used for the calculation of ADP elements embody significant uncertainty in them. This research used the CLM database’s base reserve figures [72
], as recommended in European ILCD handbook [63
]. However, the current standards [24
] do not explicitly state which reserve estimates to use, and some LCAs and EPDs may still be assessed using the ultimate reserve figures, as this has been a past recommendation [64
]. The ADP characterization factor for base reserves of copper, for example, is two times bigger than that for the ultimate reserves, for iron 30 times bigger and for aluminium, 23,000 times bigger. This makes it difficult to reliably compare the results of ADP studies between each other. However, the ADP of the case building, 1.05 kg of Antimony equivalents for almost five million kilograms (4960 t) of building materials can be compared to the production of some basic metals from virgin raw materials. The production of 420 kg of copper, 41,500 kg of aluminium, or 630,000 kg of iron from virgin raw materials would produce the same ADP of 1.05 kg [72
]. These comparisons suggest that the result for ADP of the building is of very low level.
Only 0.7% of the abiotic material inputs of the case building have a characterization factor in the first place, making the ADP elements assessment practically worthless. The basic issue behind this is that such factors cannot be defined for any of the common building materials, such as gypsum, silica sand, construction sand, clays, limestone, and such, due to lack of data on material configurations, reserves, reserve bases and ultimate reserves for these materials [65
]. Based on the results of the case-study, the benefits and purpose of calculating ADP elements for buildings is highly questionable in its current form. Methods, which would better account for local scarcity of resources [37
] or land or social impacts [38
], could fit the purpose better.
The assessment of advanced building systems resulted in ADP elements of 0.12 kg. For solar panels, the figures were 180 and 180,000 kg of Antimony equivalents. The results of advanced building systems show that such systems may be of relatively high importance, compared to the building itself.
The case-study of this research also assessed the APD Fossil for the materials of the case-building. The uncertainties related to these calculations, concerning the material quantities and the used LCI database are the same, which were discussed previously for ADP elements. As ADP fossil is defined in terms of non-renewable energy, the problem of characterization factors does not have an effect on the results. The assessment results showed that the material-related ADP Fossil totalled from 17,600 GJ (5.75 GJ/m2
) to 24,000 GJ (7.84 GJ/m2
). Research on similar buildings is limited but, for example, results of two residential buildings with concrete frame and floor area of some 1200 m2
in Sweden, show embodied energy from 4.6 to 5.4 GJ/m2
], as summarized in Ramesh et al
]. It should be pointed out that the embodied energy figures are not directly comparable to the ADP fossil figures, as the ADP fossil does not include the use of renewable energy.
The ADP fossil due to operational energy totalled to 38,700 GJ (12.65 GJ/m2
) in the case-study. The results show that the material-related non-renewable energy consumption of the case building was at the level of 30% to 40% of lifetime total non-renewable energy consumption. These results are in line with a GHG assessment of the same building, done in a previous research, showing that material-related GHG emissions accounted for 40% to 50% of lifetime total emissions [28
]. The comparable result is largely explained by the fact that GHG emissions are mainly due to consumption of fossil energy resources. As discussed above, ADP fossil does not contain renewable energy. In Finland, for example, the share of renewable energy sources in energy production was 27% in the year 2010 [91
The operational energy consumption (end-use of energy) was assessed based on standard consumption figures, stated in Finnish regulations. The energy consumption of the case building was 105 kWh/m2
. The real consumption figures may vary from this significantly, due to user behavior, as shown in previous research [92
]. However, assessment of user behavior was not the focus of this study and this variation was not considered in the assessment. In order to convert the end-use of energy into non-renewable primary energy use, Finnish national-level energy production information was used [89
] and, in order to take the future development towards low-emission energy production, conversion factors based on [28
] were used. Whereas the present-day ratio of non-renewable primary energy to end-use of energy can be thought to be a relatively reliable figure, the future conversion factors depend on political decisions in the future and cannot be predicted accurately. For example, a decrease of 25% in these factors would impact the results significantly, indicating higher than expected share of renewable energy in the future and lower than expected share of non-renewable energy. For the case-study, such change would decrease the ADP fossil from operational energy use from 12.65 GJ/m2
to 9.5 GJ/m2
. This would increase the role of material-related energy consumption from the level of 35% to 45% of lifetime totals.
The study was founded on the premise that the importance of material efficiency is based on one or more of the following impacts:
the depletion of raw materials and its long-term socio-economic impacts;
land use change due to the extraction of raw materials and its environmental impacts and impacts on the landscape and future recreational use;
the use of energy in production processes of materials and depletion of non-renewable energy;
harmful emissions from production processes of materials and their local and/or global environmental impacts;
material cost impacts due to the limited availability of raw materials or a higher need for energy and/or labor in the different phases of production processes.
This research did a comprehensive literature study to outline and draw conclusions about different aspects of the material efficiency of buildings.
Material efficiency is a complex issue to deal with in steering because there is no widely acknowledged way to make different materials commensurable. The impacts of material efficiency extend to all the aspects of resource efficiency, as shown with Equation (1) of this paper. The demand for new buildings is influenced by their durability, service life and flexibility. The use of lightweight structures impacts the average mass per product, and the yield ratio is affected by material losses on the building site. Finally, the use of secondary materials typically reduces the emissions from production. Due to the comprehensive nature of material efficiency, the focus of policy formulation should not be on its individual components, such as yield rates, average masses per products, and such, but on the impacts caused by material efficiency. Söderholm and Tilton [14
] argue similarly, that it is better to avoid policies that directly encourage specific material efficiency options, and that policies should address particular environmental problems and information externalities to enhance material efficiency in instead.
The study was founded on the premise that the importance of material efficiency is based on some of its impacts. The importance of the different impacts (indicated with indicators) can be viewed from the perspective of sustainable development. An indicator can be validated as applicable to sustainable building if it fulfils two minimum requirements: it must be related to a subject of concern for sustainable development, and buildings must have a significant impact on that issue [93
From the perspective of sustainable development, the greenhouse gas emissions from building sector are an example of an environmental problem, on which material efficiency has a significant impact on. Greenhouse gas emissions from building sector are a significant contributor on global warming, and material efficiency has a significant impact on the issue.
The consumption of non-renewable energy resources is near analogous to the greenhouse gas emissions, as the greenhouse gas emissions are mainly the result of consumption of non-renewable fossil energy in production processes of materials. This analogy was also partly illustrated by the results of the case-study.
However, the results on material-related land use showed that the importance of material-efficiency on land-use was practically negligible, as the footprint of the building was significantly more important than the land used for the extraction of non-renewable raw materials.
From the viewpoint of costs, the results showed that the role of materials is only small, some 10% to 40% of the construction costs. This means that both savings through improved material efficiency, and additional costs through future price increases in materials, have only a limited impact on total costs.
The construction industry consumes significant amounts of raw materials globally. However, the most common building materials are also common in nature. The results suggest that the most common building materials have no significant impact on depletion natural raw materials globally, although locally this might be important. However, the case might be different for some scarcer resources, which are used in advanced building systems. The case of non-renewable energy resources is different, as discussed previously. The material efficiency has a significant impact on the consumption of non-renewable energy resources.
The impact indicators for material efficiency should be concrete and they should indicate problems, which have global significance. As such, the resource depletion indicators of the current guidelines for buildings do not fully support this. This research suggests that the material efficiency should focus on the significant global impacts of material efficiency, not on the individual factors of it. At the present-day, global warming and greenhouse gas emissions are among the biggest global problems, on which material efficiency has a direct and significant impact on. Therefore, this paper suggests that greenhouse gas emissions could be used as an indicator for material efficiency in building.
Material efficiency is emphasized as an important aspect of sustainable building, as indicated by the inclusion of the ADP aspect in EN 15804 [24
] and EN 15978 [25
] and the inclusion of the new basic requirement for sustainable use of resources in the Construction Product Regulation [60
]. The roadmap to a resource-efficient Europe [3
] addresses buildings as one of the three key sectors. However, further research is still needed to clarify and draw conclusions about the correct indicators and methods to assess the material efficiency of buildings and construction.
This research studied the different aspects of material efficiency: scarcity, land use, and environmental impacts related to the manufacturing of materials.
The preliminary results received with the help of a comprehensive case study (which was aimed at all the materials used for the case building) revealed that basic building materials have only a minor effect on the results when assessed in terms of ADP elements (as recommended by ILCD [63
]). Approximately 99% of building materials have no effect on the ADP value, and, thus, approximately 1% of the materials (by weight) determine the results. The basic building materials that affect the results are the metallic materials used in buildings (steel, aluminium and copper). The result also showed that very minor material flows (in terms of weight), such as lamps and solar panels, may have a significantly bigger effect than any of the basic building materials, including all the metal used. The result raises questions of whether the ADP elements assessment method is appropriate for the assessment of buildings and construction. On the other hand, the ADP fossil fuel calculations were able to capture the material impacts more effectively. When comparing the ADP fossil values from material-related sources with the values from operational energy use, the share of materials accounted for approximately 30% to 40% of the lifetime totals.
Despite the relatively low impact on the depletion of abiotic resources, the building materials still have local impacts on the landscape and natural environment. The impacts of the extraction of gravel on ground water may also be substantial on local level. The impact of land use of abiotic materials is small compared with the footprint of the building. The land use of the building itself dominates the results (unless the land used for wood used for heating energy production is taken into account). If the use of wood is taken into account, its impact dominates in terms of land use and but also with regard to biodiversity impacts.
The greenhouse gas emissions from building sector are examples of environmental problems, on which material efficiency has a significant impact on. Greenhouse gas emissions from buildings are affected by all the aspects of material efficiency, and improvements in material efficiency can have significant impacts on the amount of emissions. This paper suggests that greenhouse gas emissions could be used as an indicator for material efficiency in building.