Pál Csonka Doctoral School 

Department of Mechanics, Materials and Structures

Supervisor: Dr. Szalay Zsuzsa

Life Cycle Assessment and Optimization of Buildings

Introducing the research area

In the course of the life cycle assessment of a building all of its environmental impacts are considered throughout its whole life-cycle, including the impact of the production of its building materials, the impact of the energy consumed for the operation and also the impact of its demolition or recycling. Using optimization processes, proposals can be made for the technical solutions applied both for the construction of new buildings and for the renovation of existing buildings, so that the harm to the environment be kept to minimal under the given conditions.

Brief introduction of the research place

The research is performed in the Csonka Pál Doctoral School in the BME Faculty of Architecture. The doctoral school hosts a wide range of researches in architectural engineering and in architecture science. This big variety opens promising opportunities for interdisciplinary researches.

History and Context of the Research

The study of the impact of buildings on the environment raises an increasingly wider interest worldwide. The main reason behind this is that the construction and operation of buildings plays a significant role in the consumption of the resources and raw materials in the world, and it is also responsible for a large proportion of the harmful emissions. Life cycle assessment is a tool that can be used for the study of these impacts. The whole lifecycle of a given system can be studied (in this case it includes the construction, the operation and the demolition or recycling of a building) and the total environmental impact can be summarized considering all the processes included during this period.
Thanks to the more and more serious environmental objectives, the requirements on the energetic performance of buildings is also getting stricter. [2] This has resulted in the reduction of the environmental impact in the operation phase. However, the progress in technology and in building materials, and also the increased consumption of materials result in an increased environmental impact in the construction phase.

Due to the increase of energy efficiency and to the use of locally produced renewable energy, the amount of energy required during the operation phase can be reduced even to zero. This increases the proportion of remaining phases (construction, demolition, etc.) within the total environmental impact, which can be a significant concern when summarized the building stock at the country level. Nonetheless, regulations regarding the buildings concentrate merely on the energy usage during the operation phase.[3]

The research goal, open questions

Life cycle assessment is a proper tool for the study of the overall environmental impact. However, with its application on buildings many methodological questions arise.[4, 5] A detailed analysis considers numerous processes (for example the impact of the production of the machines used for the construction). Also, a very large number of different materials should be used for the construction of a building. Therefore, to get the required information on the overall impact through reasonable effort, simplifications have to be made.[6]

Moreover, life cycle assessment can only has significant effect, if it can provide results that influences the design and minimize the environmental impact of the building. On the other hand, in the design phase there are many uncertainties about the materials, structures and operation of the building. Due to this, many estimations have to be made.

One of the objectives of the present research is to reveal the effect of these estimations and to give a methodology for the necessary simplifications to support the design of buildings. An additional objective is to demonstrate the potential in existing building stock in the reduction of harmful environmental effects.

The current research also targets questions regarding the modelling of buildings, their operation and life cycle phases, because the difference in modelling methods can affect results. The energy consumption of the building e.g. can be modelled in numerous ways, from simplified (like the static seasonal method) to more complex ones (e.g. the dynamic building energy simulation). Also there can be various modelling methods for the renovations required during the lifecycle of a building.[7]

One has to cope with numerous design variables, such as building materials, building geometry, orientation or the mechanical system of the building. Any change to them may significantly affect the life cycle assessment. To choose the optimal solution from among the numerous possibilities each having several parameters, the so called heuristic techniques were applied, that are capable of generating the quasi-optimal group of solutions of a multiparametric system. In the research the applicability of these techniques for buildings are studied.

Methods

It can be understood from the previous sections that the calculation methods used for the life cycle assessment have to be built up in a modular system. This makes it possible to select and change one variable easily (for example, different methods can be easily chosen for the calculation of the operational energy consumption). It is also important that the different modules can function in the same framework in order to give dynamic feedback that is necessary for the optimization.

The environmental impact of the buildings can be described with different indicators, such as the overall consumed resources and the overall different harmful emissions. It is important to show, which phases and which building elements are responsible for the significant consumptions and emissions. For this reason, the allocation of the indicators is also important besides their summation. In case of a complicated building and life cycle model a complex visualization of the results is necessary. In the research special attention is paid to the interpretation and visual presentation of the results.

As a further step in the research, the potential in the reduction of the environmental impact of a country or region is going to be assessed. This can be achieved with modelling the typical elements of the building stock. With the assessment of this typology, a proposal can be made for the improvement of the local regulations regarding these buildings, in order to reduce the harmful environmental impact.

Through the optimization process for different building types proposals can be made for the refurbishment scenarios [8]. An optimized model with the given circumstances can also provide guidelines for the reduction of environmental impact during the design phase of new buildings.

Constructing parametric models also allows for the testing of simplification methods to improve modelling tools, that can be used from the beginning of the design process, and that can determine the estimated environmental impact of the buildings using only a few parameters.

Results

In the first phase of the research the life cycle assessment of an existing building was performed, considering different phases of its design.[1] In each design phase the different possible versions of the buildings were compared to see how much they differ in their environmental impact. Some of the specific parameters related to the geometry of the building, the materials and the constructions of the building envelope and of the internal structures, the various mechanical systems applied, the orientation and the type of shading.

The important parameters whose change makes a considerable variation on the environmental indicators were identified. (Figure 1.) It was shown, that even in case of a one family house designed and built with energy efficiency in mind, the type of the energy source used during the operation phase plays an important role in the environmental impact.

Figure 1.

Possible values of the global warming potential of the examined building (vertical axis) in the different design stages (horizontal axis). The blue field represents the possible values. The gaps between the fields correspond to the parameters with high influence.

In the studied case the heating system (heat pump) consumes electrical energy. The application of a wood gasifying boiler instead of the heat pump would have resulted in a reduced environmental impact, regardless of the other parameters. It can be also seen from the results, that although the solutions chosen by the experts in each design phases were close to the optimal ones, still the total environmental impact could have been further reduced under the given circumstances. (Figure 2.)

Figure 2.

Possible values of the acidification potential of land and water caused by the examined building (vertical axis) in the different design stages (horizontal axis). The green field represents the optimization potential that could be achieved beyond the choice of the experts.

In the next phase of the research a modular system was created to allow using different calculation methods for the life cycle assessment. (Figure 3.) The modular system includes geometric modelling, the definition of building parameters (materials, structures), and the definition of the building mechanical system, the energy calculation and the calculation of environmental impacts.

Figure 3.

The structure of the modular system that enables the usage of multiple calculation methods in the different modules.

With this system, different visualization methods were elaborated for the evaluation of results. A case study was prepared to demonstrate the method of assigning environmental impacts to various life-cycle phases, and also to the structural elements in each phase. This resulted in a hierarchical assignment. (Figure 4.)

 

Figure 4.

The hierarchic representation of the cumulative energy demand of the examined building.

This presentation of results enabled identification of the phases whose change can reduce the overall impact. Furthermore, with the help of 3D visualization, the structural parts from the same aspect could also be identified. (Figure 5.)

Figure 5.

The 3D representation of the environmental impacts of the surfaces and constructions.

With the 3D model the energy performance of each structural part can be also shown (Figure 6.), giving a clue about the locations where the building performance can be easily improved.

 

Figure 6.

The 3D representation of the energy performance: heat losses (left) and solar gains (right).

Expected impact and further research

The developed system and visualization method makes it possible to easily move towards the next steps of the research described above. Beyond these steps it will be also possible to develop guidelines for designers, who can use them in their everyday practice. It would be also reasonable to develop a simulation system that can consider the change in the economical and climatic conditions during the long operation phase of the building. The availability and accessibility of non-renewable resources could be also considered.

 

Publications, references, links

Own Publications:

[1]   B. Kiss and Zs. Szalay, The Impact of Decisions Made in Various Architectural Design Stages on Life Cycle Assessment Results, Applied Mechanics and Materials 861 (2016) pp. 593–600.

 

Bibliography:

[2]   European Commission, Resource efficiency opportunities in the building sector (2014) p. 10.

[3]   A. Zöld, Zs. Szalay, What is missing from the concept of the new European Building Directive? Build. Environ. 42 (2007) 1761–1769.

[4]  M. Buyle, J. Braet, and A. Audenaert, “Life cycle assessment of an apartment building: Comparison of an attributional and consequential approach,” Energy Procedia, vol. 62, pp. 132–140, 2014.

[5]  S. Lasvaux, J. Gantner, B. Wittstock, M. Bazzana, N. Schiopu, T. Saunders, C. Gazulla, J. A. Mundy, C. Sjöström, P. Fullana-i-Palmer, T. Barrow-Williams, A. Braune, J. Anderson, K. Lenz, Z. Takacs, J. Hans, and J. Chevalier, “Achieving consistency in life cycle assessment practice within the European construction sector: the role of the EeBGuide InfoHub,” Int. J. Life Cycle Assess., vol. 19, no. 11, pp. 1783–1793, 2014

[6]   A. Hollberg and J. Ruth, “LCA in architectural design—a parametric approach,” Int. J. Life Cycle Assess., vol. 21, no. 7, pp. 943–960, 2016.

[7]  A. Passer, H. Kreiner, and P. Maydl, “Assessment of the environmental performance of buildings: A critical evaluation of the influence of technical building equipment on residential buildings,” Int. J. Life Cycle Assess., vol. 17, no. 9, pp. 1116–1130, 2012.

[8]  A. Vilches, A. Garcia-Martinez, and B. Sanchez-Montañes, “Life cycle assessment (LCA) of building refurbishment: A literature review,” Energy Build., vol. 135, pp. 286–301, 2017.

[9]  C. Roux, P. Schalbart, E. Assoumou, and B. Peuportier, “Integrating climate change and energy mix scenarios in LCA of buildings and districts,” Appl. Energy, vol. 184, pp. 619–629, 2016.