In order to help the building and construction sector move towards a Circular Economy and lower its environmental impact, a better founded choice regarding the design and selection of building materials for a building’s load bearing structure is required. By investigating different design strategies that focus on optimizing various aspects of the Circular Economy, an office building can be designed in such a way that it matches both the initial client’s requirements as well as possibly changing future needs. Different design strategies then lead to varying lay-outs of a building’s load bearing structure and the building material it’s made of.
By ranking ten design perspectives in varying orders, three main design strategies can be formed. The first one maximizes a building's technical service life, thereby limiting the use of new materials and energy during maintenance activities. The second strategy aims for a maximal functional service life, by making the original building fit for possible other functions in the future. The final strategy maximizes a building's residual value, which includes re-use of building elements in new projects.
The next step is to link these design strategies to various criteria that can be included in the Multi Criteria Analysis. This results in a total of nine criteria, some of them being linked to the characteristics of a building material and the type of connections that come with that material. Other criteria depend on the design of a load bearing structure, such as the total weight of a structure, its ECI value and a cost indication. Now, all these MCA criteria can be given different weights, according to their level of importance per design strategy.
Finally, the MCA as explained above, can be tested on a case study from Witteveen+Bos. Based on the Program of Requirements as formulated by the client, both design strategy 2 and 3 could be followed during the design phase. The main difference between these two strategies can clearly be seen in the lay-out of the load bearing structure’s. After completing the MCA for both strategies, it can be concluded that a bolted steel structure is most likely the best option for design strategy 2. On the other hand, a bolted CLT structure seems to be the best solution when designing according to design strategy 3 for this specific case study. Concluding these results, it can be stated that the MCA can indeed help in selecting a design and building material, however in some cases, the differences between some building materials seem limited. Therefore, it can be said that the MCA is more likely to be helpful in eliminating some of the building materials from next design steps, based on their low MCA results.