LCA of three structural solutions of a building in the University of Aveiro
CASE STUDY
The case-study is the most recent building of art and communication department of Aveiro University, which aims to provide a creative educational environment for its students and professors throughout its halls, auditorium and classrooms. It was selected since it pretends to be an example of a scholar sustainable building. The underground floor is composed by backstage rooms situated below the auditorium. The ground floor has two distinct parts: an auditorium with all its supporting areas, such as the toilets, halls and circulations; and a scholar part with 7 classrooms and laboratories. The first floor consists of the rest of the auditorium and their supporting rooms and circulations, which vertically occupies the same area as in the ground floor. Like the ground floor, there is also a scholar part with 2 classrooms, 1 studio, 2 laboratories and 2 offices, with an open zone between them. The second and the last floor is only dedicated to scholar purposes. It has a big room for the researchers and the PhD students and 12 classrooms for design, a students’ room and offices. The building is mixed superstructure of steel and concrete. Concrete piles foundations majorly compose its foundations. The basement floor has a concrete foundation slab and concrete bearing walls. The superstructure beams and columns are mainly in steel and there are 20 steel bracing systems. The slabs in first and second floors are collaborative of steel and concrete. Finally, the building has three metallic staircases supported by steel beams and columns. The goal of present study is to compare the environmental impacts of three types of structures (mixed structure, only steel structure, only reinforced structure). Those three alternatives are pre-designed using the Eurocode and studied according to two life spans 50 and 100 years, considering the maintenance requirements and the design needs for each life span as it is recommended in E464 LNEC. Finally, those six alternatives are analysed using SimaPro as an advanced-level LCA tool ad presented in Table 1.
Table 1. Description of the six alternatives analysed by LCA using SimaPro
Alternative Description Life Span Design
1 Real case study (mixed) 50 years life span 100 years life span 2 Only steel structure 50 years life span
100 years life span 3 Only reinforced concrete 50 years life span
100 years life span
The three alternatives were modelled using Revit as a BIM tool to provide the study with the quantities of each material in each alternative. Figures 4, 5 and 6 represent 3D BIM models of the three alternatives.
Figure 4. 3D Revit model of alternative 1
Figure 5. 3D Revit model of alternative 2
Figure 6. 3D Revit model of alternative 3
In Table 2, the main results of inventory analysis are presented, comparing the design material and material in SimaPro database.
Table 2. Inventory analysis of materials database
Alternative Description SimaPro Classification
Concrete in collaborative
slabs C20/25, XC3+XS1 C20 with a density of 2335
kg/m3.
Concrete in solid slabs C35/45, XC4+XS3+XA2 C35 with a density of 2315 kg/m3.
Concrete in foundations C35/45, XC4+XS3+XA2 C35 with a density of 2315 kg/m3.
Concrete for 100 years
design C45/50, XC4+XS3+XA2 C50 with a density of 2300 kg/m3.
Steel Hot rolled Steel Steel, hot rolled, low alloyed steel
Wood Plywood Plywood, outdoor use
Painting Epoxy with zinc Only zinc coating
After selecting the materials and describing them in the previous table according to how they are classified in SimaPro, it is important to explain how the impacts assessment was calculated which is presented in Table 3.
Table 3. Life cycle impact methodology Material name Functional
unit Category indicator per
functional unit Total value Concrete in all the
elements m3 Category indicator value per
1 m3 Quantity (m3) x Category
indicator value per 1 m3 Concrete for piles m Category indicator value per 1 m Quantity (m) x Category
indicator value per 1 m
Steel kg Category indicator value per
1 kg Quantity (kg) x Category
indicator value per 1 kg Painting m2 Category indicator value per
1 m2 Quantity (m2) x Category
indicator value per 1 m2 Formwork m2 Category indicator value per
1 m2 Quantity (m2) x Category
indicator value per 1 m2 To compare the results of the different alternatives in this study, Table 4 present LCA environmental impacts per each alternative.
Table 4. LCA environmental impacts per alternative
Impact Category Alt.1.1 Alt.2.1 Alt.3.1 Alt.1.2 Alt.2.2 Alt.3.2
kgCFC-11 eq 0.219 0.235 0.163 0.206 0.219 0.130
kgCO2eq 2.726 x106 2.945 x106 2.137 x106 2.719 x106 2.841 x106 2.038 x106 kgO3eq 1.712x105 1.860 x105 1.157 x105 1.668 x105 1.772 x105 1.018 x105 kgSO2eq 1.468 x104 1.630 x104 6.890 x103 1.460 x104 1.577 x104 6.485 x103 kgNOx eq 1.322 x104 1.581 x104 5.290 x103 1.307 x104 1.503 x104 4.850 x103 Comparing the six alternatives it is concluded that the reinforced concrete alternative is environmentally more sustainable than the mixed and the steel structure, respectively. Moreover, the table shows that the 100-year design has less environmental impacts than the 50-year design, highlighting that materials with high environmental impacts and maintaining once could compensate the use of materials with lower environmental impacts and maintaining twice during the life span.
However, since these results are specifically regarding this case study, that table does not allow the comparison with other buildings and studies. Therefore, in order to compare them with other studies’
results and validate them, it is essential to divide them by the constructed area (m2). Therefore, the results per square meter are presented Table 5.
Table 5. LCA impacts of each alternative per m2
To validate the results, since it is a numerical way of comparing them with the results of similar studies regarding similar structural solutions. Thus, Ngo et al. (2009) showed that the global kg CO2eq emissions per m2is almost 470 for a concrete building and 780 for a steel framed building. In this study, the concrete alternative is responsible for 454 and 433 kg CO2eq per m2, which are very close to Ngo et al. (2009) results.
CONCLUSION
This work began highlighting the need to achieve more sustainable buildings, since they largely contribute to important environmental impacts, such as global warming and ozone depletion and their energy consumption must be substituted by more sustainable alternatives. Therefore, these requirements culminate with the necessity of LCA calculation in the construction sector, since LCA methodology can successfully predict the environmental impacts of the materials and the processes.
However, applying LCA in the construction sector has various obstacles, such as its complexity since it is needed to consider the enormous number of materials and components used in the building.
Moreover, it is not possible to get all the correct data in LCA database which makes LCA calculations have uncertainty in the results. In addition, LCA calculations do not consider the social aspects and the accidents that could harm the human life in the construction site and it does not consider the indoor impacts nor the workplace emissions.
The previous results highlight that the concrete alternative, which is the most common structural solution used in Portugal, has less environmental impacts comparing with the other two structural solutions. In addition, it highlights the vital impact of maintenance, since maintaining once in 100-year design and using materials with high environmental impacts could compensate maintaining twice and using materials with lower environmental impacts in a 50-year design.
Finally, considering more durable and more sustainable buildings highlights the necessity to study different maintenance methods for the concrete structure, since it is a basic material in the construction sector, particularly in Portugal and its impacts cannot be neglected.
AKNOWLEDGMENT
Authors thank SUCCESS project for sustainable constructions applying geothermic superficial systems and for the scholarship program of Global Platform for Syrian Students for the generous finance, which allowed the first author to continue her higher education and obtain a master degree in Civil engineering in University of Aveiro.
Impact Category Alt.1.1 Alt.2.1 Alt.3.1 Alt.1.2 Alt.2.2 Alt.3.2 kgCFC-11 eq/m2 4.653x10-5 4.993x10-5 3.463x10-5 4.376x10-5 4.653x10-5 2.762x10-5 kgCO2eq/m2 5.791 x102 6.257 x102 4.540 x102 5.777 x102 6.036 x102 4.330 x102 kgO3eq/m2 3.637 x101 3.952 x101 2.458 x101 3.544 x101 3.765x101 2.163 x101
kgSO2 eq/m2 3.119 3.463 1.464 3.102 3.35 1.378
kgNOx eq/m2 2.809 3.359 1.124 2.777 3.193 1.030
REFERENCES
Assefa, G. and Ambler, C. (2017) ‘To demolish or not to demolish: Life cycle consideration of repurposing buildings’, Sustainable Cities and Society. Elsevier B.V., 28, pp. 146–153.
Basten, V., Latief, Y., Berawi, M. A., Budiman, R. and Riswanto (2017) ‘Evaluation of green building rating tools based on existing green building achievement in Indonesia using Life Cycle Assessment Method’, (March), pp. 1-11.
Bastos, J., Batterman, S. A. and Freire, F. (2014) ‘Life-cycle energy and greenhouse gas analysis of three building types in a residential area in Lisbon’, Energy and Buildings. Elsevier B.V., 69, pp. 344–
Bragança, L. and Mateus, R. (2012) Life-Cycle Analysis of Buildings: Environmental impact of building 353.
elements.
Brás, A. and Gomes, V. (2015) ‘LCA implementation in the selection of thermal enhanced mortars for energetic rehabilitation of school buildings’, Energy and Buildings. Elsevier B.V., 92, pp. 1–9.
Ferreira, J., Duarte Pinheiro, M. and De Brito, J. (2015) ‘Economic and environmental savings of structural buildings refurbishment with demolition and reconstruction - A Portuguese benchmarking’, Journal of Building Engineering. Elsevier, 3, pp. 114–126.
Gervásio, H. and Silva, L. S. da (2008) ‘Comparative life-cycle analysis of steel-concrete composite bridges’, Structure and Infrastructure Engineering, 4(4), pp. 251–269.
Kulahcioglu, T., Dang, J. and Toklu, C. (2012) ‘A 3D analyzer for BIM-enabled Life Cycle Assessment of the whole process of construction A 3D analyzer for BIM-enabled Life Cycle Assessment of the whole process of construction’, HVAC&R Research, 18:1-2(October 2014), pp. 37–41.
Ortiz, O., Castells, F. and Sonnemann, G. (2009) ‘Sustainability in the construction industry: A review of recent developments based on LCA’, Construction and Building Materials. Elsevier Ltd, 23(1), pp. 28–39.
Patrick, H. (1998) Perspectives in Life Cycle Impact Assessment. 1st edn. New York: Kluwer Academic Publishers.
Reza, B., Sadiq, R. and Hewage, K. (2014) ‘Emergy-based life cycle assessment (Em-LCA) of multi-unit and single-family residential buildings in Canada’, International Journal of Sustainable Built Environment. The Gulf Organisation for Research and Development, 3(2), pp. 207–224.
Rodrigues, C. and Freire, F. (2017) ‘Building retrofit addressing occupancy: an integrated cost and environmental life-cycle analysis’, Energy and Buildings. Elsevier B.V., 140, pp. 388–398.
Santos, P., Gervásio, H., and Silva, L. S. da (2016) ‘A simplified tool to evaluate the sustainability of buildings in steel in early stages of design’, Matériaux & Techniques., 104, pp. 103.
Silvestre, J. D., Pargana, N., De Brito, J., Pinheiro, M. D. and Durão, V. (2016) ‘Insulation cork boards-environmental life cycle assessment of an organic construction material’, Materials, 9(5), pp. 1–16.