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Resource efficient construction towards Sustainable Design

Periodic Reporting for period 1 - EFIResources (Resource efficient construction towards Sustainable Design)

Reporting period: 2016-09-01 to 2018-08-31

The built environment is responsible for a high global share of environmental, economic and social impacts. Therefore, the standard practices of the construction of buildings are jeopardizing the chances for future generations to meet their own needs.
The research project EFIResources: Resource Efficient Construction towards Sustainable Design, supports European policies related to the efficient use of resources in construction and its major goal was the development of a performance based approach for sustainable design, enabling to assess resource efficiency throughout the complete life cycle of buildings and complying with the design rules and reliability provisions of the Eurocodes.
To fulfil this goal four major achievements were foreseen as follows:
• Definition of benchmarks for the life cycle environmental performance of buildings to provide a consistent and transparent yardstick for the assessment of the environmental performance of buildings and to strive towards an effective reduction of the use of resources and relative environmental impacts in the building sector;
• Development of a LCA model, based on the standardized framework for LCA developed by CEN TC 350, to assure consistency in the development of the benchmarks;
• Development of the performance-based approach for sustainable design, in which the performance of the building is benchmarked against standard and/or best practices;
• Identification of further technical, research and standardization needs to better address the resource efficiency opportunities in the building sector.
The approach is limited to the structural system of buildings. One of the reasons for this limitation is the lack of environmental data to enable an accurate life cycle analysis of the full building.
1. Model for the quantification of benchmarks

A graduated approach was adopted for the benchmarks, starting on a simple basis and being refined and increasing in complexity over time, as data collection on buildings and relative processes becomes more complete and precise.
The benchmarking of buildings is thus an evolving process as illustrated in Figure 1, and the main steps of approach are:
Step 1) Definition of objectives and scope
Step 2) Data collection
Step 3) Quantification of benchmarks
Step 4) Setting of benchmarks
In this project, benchmarks were developed, based on the statistical analysis of the sample of buildings collected in the project.
Moreover, ‘conventional’ practice is assumed to be given by the median value of the environmental performance of the buildings; while, ‘best practice’ is assumed to be given by the value of the environmental performance that is achieved by only 25% of the buildings, i.e. the upper limit of the first quartile, as illustrated in Figure 2.

2. Limit state of sustainability

The European standards for structural design are based on the limit state concept, which consists on the definition of structural and load models for relevant ultimate and serviceability limit states.
In this project, a performance-based approach for sustainable design was introduced, which enables to assess the efficient use of resources in buildings throughout the complete life cycle of the building, and complies with the Eurocodes.
In this case, a structure shall be designed in such a way that it will with appropriate degrees of reliability, in an economical way and with low environmental impacts, attain the required performance’. Therefore, the aim of the proposed approach is the pursuit of a building design with a lower environmental performance than a reference value, represented by the average performance of the same type of buildings, in a given area.
Hence, in this model two variables are defined: (i) the environmental performance of the building being assessed (E) and (ii) the reference value (R) of the environmental performance of a set of buildings, in a given area. In this case, taking into account the goal of the approach, the condition that should be satisfied is E ≤ R.
In this case, a limit state function may be defined by S = E – R and therefore, S = E – R ≤ 0.
However, both variables are quantified based on a life cycle approach and therefore, they are subjected to a high degree of uncertainties and variabilities not only due to the long life span of buildings but also due to the inherent uncertainties in life cycle approaches. These uncertainties are taken into account in the analysis and therefore, both variables are defined by respective probability density functions, as represented in Figure 3.
In this case, the probability of achieving a good environmental performance, i.e. the probability of achieving an environmental performance better than the reference one, is given by P{f(S)≤0}.
This new limit state is denominated sustainability limit state and it is complementary to the ultimate and serviceability limit states referred above for structural design.

3. Results of the project

The calculation of benchmarks was based on the statistical analysis of the buildings collected in the scope of the project.
It is important to highlight that the quality and robustness of benchmarks, based on a statistical analysis, is strongly dependent on the quality and representativeness of the sample in relation to the ‘basic population’. However, the number of buildings collected in this project is reduced and does not enable a proper statistical analysis. In spite of this limitation, the set of values obtained in the project was used to demonstrate the approach for sustainable design.
Focussing on the results of the initial sages (modules A1-A3) and the results of the complete life cycle (A1-D), the range of values are indicated in Figure 4 and Figure 5, for the impact c
According to the developed approach for sustainability design, the performance of the building is benchmarked against standard and/or best practices. This approach provides major innovations with respect to other available methodologies:
• The model for the assessment of buildings is based on a standardized procedure for LCA, thus enabling comparability and benchmarking;
• The approach is meant to be used in early stages of design so that proper decisions, with regard to design options, can be made in the most influential stages of design;
• The methodology enables a widespread application within building designers, without the need of a great level of expertise;
• The approach for sustainability design complies with the design rules and reliability provisions of the Eurocodes, thus enabling the harmonization between structural safety and sustainability in the design process;
• The approach addresses the new basic requirement of “sustainable use of natural resources” of the Construction Products Regulation (Regulation (EU) No 305/2011) and therefore, it ensures the full implementation of this regulation;
• The development of benchmarks for the environmental performance of buildings will enable to set consistent targets for the reduction of the consumption of resources and other environmental problems.
The results of this project will facilitate the incorporation of sustainability criteria in construction practices in consistence with the safety requirements of the design standards, thus providing building designers with an approach for safe and clean construction.
Figure 2. ‘Conventional’ and ‘best’ values
Figure 4. Range of values for GWP and PE in A1-A3 and A1-D, residential buildings
Figure 5. Range of values for GWP and PE in A1-A3 and A1-D, office buildings
Figure 3. Probability density functions of the design environmental performance [fE(e)] and of the r
Figure 1. Graduated approach for benchmarking of buildings (based in [10])