Erich Wutscher (2017), Dismantling and recycling in the building sector – An approach assessing the example of the cross-laminated timber system, Institute of Architecture Technology; reviewer: Roger Riewe, Stefan Peters, Mike Schlaich; 242 pages, German.
The building sector claims responsibility for a majority of the consumption of resources and the resulting consequences for the environment. The recycling of building materials and products is considered a necessary step in order to increase resource efficiency and to avoid the negative consequences on the environment stemming from reproduction of materials. The lack of dismantling capacity of usual construction methods does however not allow diverse separation and segregation of the used materials and components in the end, so that the materials could be reused. As a result, valuable raw materials and energy become waste and are lost on disposal sites. Since wood is a showing building material that maintains an extra position due to its high potential to relieve climate and environment over all life cycle phases. Modern wood building systems such as the cross-laminated timber building system still have to utilize other products of different consistency in order to withstand the various requirements of construction. Therefore, a building with a cross-laminated building system includes a huge number of building materials of various categories of material, which also need to be dismantled before valuable recycling. It is the aim of this thesis to determine the dismantling capacity of the cross-laminated timber system and the recycling capacity of the used components with the help of suitable criteria as well as an analysis, assessment, and optimization. The focus for the valuation of the recycling capacity is going to lie on the structural level of the cross-laminated timber building system – for the evaluation of the dismantling capacity as well as on the substance level of the used materials and building materials. Methods for operationalization and dismantlement - as well as recycling capability have not been dealt with thoroughly by the construction industry. Therefore, the aspects of dismantling are going to be analysed on the basis of Durmisevic’s evaluation model, which provides the requirements for a building structure, which can be dismantled on a structural level. The requirements for the recycling compatibility on a substantial level are based on Brenner’s analysis of aspects for substantial exploitability. Resulting from this analysis, altogether 16 criteria are defined with 11 of them serving the assessment of the dismantling capacity and 5 serving the assessment of the recycling capability. The results of this thesis show that the structural composition of the cross-laminated timber building system is able to be dismantling – as well as recycling – friendly. The whole system is separated into parts and subparts (main body-in-white systems, enveloping surfaces, development elements and building technique), whose ranking can be determined in accordance with their substitution cycle. As a result, positive effects cannot only be expected in the rebuilding phase but also in the utilization phase. Parts and subparts can be adapted, exchanged and overhauled separately without impairing the system as a whole. The body-in-white system, on the other hand, is composed out of parts with different substance categories and lifespans, which complicate the dismantling – and recycling process due to mutual dependence and firmly bonded connections. The actual dismantling ease and recyclability of the whole system is determined by the dismantling ease and recyclability of the enveloping surfaces, the developing elements and the integration into the building technique. The many possibilities of the multi-layer constructions, the substance combinations and the connections resulting from those as well as their dependencies on each other as well as the dependency on the multi – layer construction require individual consideration of the respective parts and subparts.