Introduction
The kindergarden is a low-rise building and is intended to contribute to environmental awareness, which is why timber, a climate-neutral and sustainable building material, is used for the construction. Overall, the construction of the kindergarden is as follows:
– Timber columns
– Timber roofs
– Timber walls
– Reinforced concrete foundation
The use of timber creates a comfortable and natural learning atmosphere for children. In addition, timber has positive effects on health, as wood binds pollutants from the air and can thus prevent stress and diseases such as asthma [1].
Goal and Scope
The goal of the following assessment is to do an energy and emission analysis. By examining different design options, the design option with the least amount of CO2, NOx, and SO2 emissions can be identified.
Furthermore, the scope and the boundaries are shown in Figure 2. In general, the scope defines what processes and boundaries are necessary to achieve a certain goal. Since the goal of this work is the analysis of energy consumption and greenhouse gas emissions, all parameters that have an influence were included, e.g. raw materials, production and maintenance.
For the frame construction, three different material design options were selected and are presented in Table 1.
To contribute to environmental awareness, the first chosen design option is timber. It is a climate-neutral and sustainable building material. Moreover, the use of wood creates a pleasant and natural learning atmosphere for children [1].
The second option is a steel frame. Steel is a strong material that does not deteriorate over time as other materials. In addition, steel is fireproof and termite resistant. It is also sustainable as it is 100% recyclable and generates less landfill waste [5].
Furthermore, the third design option is a reinforced concrete frame. The benefits of reinforced concrete material are its resistance, low maintenance costs and limitless range of shape [6].
Life Cycle Timeline
The timelines of the three design options are presented in Figure 3. Since a kindergarden lifetime is between 50 and 75 years [7], the timeline of the frame is considered to be approximately 60 years. Moreover, the maintenance work, which is marked with the letter M, is carried out every 5 years for the timber frame and every 6 years for the other design options. The frequency of maintenance work for timber is shorter, because of its higher deterioration caused by biotic agents like e.g. bacteria or insects and abiotic agents like e.g. sun or water [8].
Life Cycle Inventory and Cost Analysis
The results of the cost analysis showed that the timber frame has the lowest costs for energy consumption and emissions. The main reason for this is that out of all design options, the timber frame has the smallest volume. In addition, the second-best choice is steel, followed by reinforced concrete.
Moreover, the CO2 emissions have the highest value among all greenhouse gas emissions. This is because the total carbon footprint of the construction industry in Germany is 398 million tons, which corresponds to about 40% of all greenhouse gases [9]. The results for CO2 consumption are also consistent with other reference buildings [10]. Others also concluded that wood has the lowest CO2 emissions compared to steel and concrete (see Figure 4).
![Figure 4 CO2 Emissions of Reference Buildings [10]](http://130.149.22.198/wp/wp-content/uploads/2023/02/Bildschirmfoto-2023-02-02-um-21.56.43.png)
Multi-Criteria Decision Making (AHP)
The result of the AHP method is presented in Figure 5. It can be seen that option 1 covers 46.2%, option 2 covers 33.2% and option 3 covers 20.6%. Accordingly, among all design options, options 1 has the highest ranking. However, it has to be mentioned that in this analysis only the environmental aspects were considered. If other important aspects like durability or strength were considered, the results possibly would vary. In that case, steel and reinforced concrete would be more advantageous than timber [8].
References
[1]: Korte Holzbau & Zimmerei KG; Natürlich und schön, Kita’s aus Holz für gesundes Spielen und Lernen: https://www.korte-holzbau.de/objektbau/kitas.html; [last accessed: 24.11.2022].
[2]: The European Centre for Architecture Art Design and Urban Studies; Wooden kindergarten loce – Matic Lašič – Slovenia (Archive 2008): https://www.europeanarch.eu/europe-40-under-40-awards-archive/2019/05/23/wooden-kindergarten-loce-matic-la%C5%A1i%C4%8D-slovenia/; [last accessed: 02.02.2023].
[3]: Beilhammer, Marius; Kindergarten bauen: Richtlinien 2021: https://www.architektur-welt.de/ kindergarten-bauen-richtlinien/#verbotene-materialien-beim-kindergarten-bauen; [last accessed: 02.01.2023].
[4]: Technical University of Berlin; Course: Whole Life Civil System Analysis WS22/23, A Bridge Example (2022).
[5]: JG King Homes, 6 Benefits of Steel-Framed Housing (March 2018): https:// jgkinghomes.com.au/blog/6-benefits-of-steel-framed-housing; [last accessed: 09.01.2023].
[6]: Ocmulgee Concrete Services, Benefits of Using Reinforced Concrete in Construction: https:// ocmulgeeconcreteservices.com/raleigh-services/benefits-of-using-reinforced-concrete-in- construction/; [last accessed: 09.01.2023].
[7]: Wirtschaftliche Nutzungsdauer von Gebäude: https://www.bauprofessor.de/wirtschaftliche- nutzungsdauer-gebaeude/; [last accessed: 25.11.2022].
[8]: SkyCiv Engineering, Commonly Used Materials in Structural Engineering (February 2019): https://skyciv.com/technical/steel-vs-timber-vs-concrete/ [last accessed: 13.01.2023].
[9]: Bauindustrie, Energieverbrauch und Klimaschutz im Baugewerbe – Eine Datensammlung (2022): https://www.bauindustrie.de/zahlen-fakten/auf-den-punkt-gebracht/energieverbrauch-und-klimaschutz-im-baugewerbe-eine-datensammlung; [last accessed: 14.01.2023].
[10]: MANTLE Developments, Mass Timber’s Carbon Impact (November 2020): https://mantledev.com/insights/embodied-carbon/mass-timber-carbon-impact/; [last accessed: 14.01.2023].