Reuse of building components benefit the environment as well as construction costs

Tuesday 05 Jul 16


Arne Egerup
External lecturer
DTU Civil Engineering
There are big savings in reusing building components in their original form rather than crushing them and recycling the components as road fill, for example. The savings apply to both the environment and the costs of a building project. That is the conclusion in a thesis written by two graduate students, who recently won 1st prize for best master thesis concept at DTU's student competition Green Challenge.

Sara Diraoui and Leonora Charlotte Malabi Larsen, who are students in Civil Engineering and Architectural Engineering respectively, recently won 1st prize in DTU's student competition Green Challenge with a presentation of their joint master’s thesis entitled "Design for Disassembly - Building a circular future".

The basic idea of the thesis is to design buildings in a way that enables reuse of building components to a much greater extent than today. The thesis was written in cooperation with MT Højgaard and the architectural firm 3Xn, who had asked the two students to examine construction technology and sustainability aspects regarding reuse of building components.

Prefabricated products present good application options

One of the benefits of the solution that Sara Diraoui and Leonora Charlotte Malabi Larsen demonstrate in their thesis is that they use components that are already on the market today and therefore does not require an introduction of new materials and components. In their thesis the two students introduce a new way to reuse components, so they can be more easily reused as intact building components in new buildings.

"The project team behind "Building a circular future" has found a new way to use an existing prefabricated solution. Instead of casting concrete walls together, it is possible to use components to assembly the walls. This technique allows you to create a layered removal of the concrete elements and thus make it easier to reuse them, "explains Sara Diraoui.

This method should have a place in future building practices, is the assessment from Arne Egerup, External Lecturer at DTU Civil Engineering and supervisor on the thesis.

"The thesis makes extensive use of design tools of the type Computer Aided Design (CAD), which makes it easy to optimize the design in terms of strength and stiffness and stress analysis of joint details. The easier separation of structures and components makes it easier to reuse the materials, and it becomes possible to achieve significant financial savings and less environmental loads and thereby come close to the "zero waste" concept, where no construction waste goes to waste, says Arne Egerup.

Great environmental savings

Building materials are usually recycled in a way that is popularly known as "down-cycling". In the case of concrete, this means that building materials are crushed and recycled as gravel in asphalt and the like. In the thesis "Design for Disassembly" the concrete is reused in its original form: as construction components in new buildings.Graphics: Sara Diraoui and Leonora Charlotte Malabi Larsen

There are great environmental savings by choosing this type of reuse over recycling and thus down-cycling.

"Our findings suggest that concrete components that are reused three times can result in a saving of between 33 and 60 per cent in greenhouse gas emissions and thereby climate impact compared to single use of the components and subsequently down-cycling. This direct form of reuse can also save money in the construction process, since it is cheaper to reuse existing concrete components rather than create new components from scratch, "says Leonora Charlotte Malabi Larsen.

Sustainability must be quantified

To incorporate sustainability as an element in building design is obvious to for DTU as a technical university, says Morten Birkved, Associate Professor at DTU Management Engineering and supervisor on Sara Diraoui and Leonora Charlotte Malabi Larsen's thesis.

Morten Birkved works with Life Cycle Assessment (LCA); a method that implicates the entire life cycle of a product, service or in a project like in this case. The LCA approach is popularly called "cradle to grave" assessment. He emphasizes that the approach to sustainability must be constructive, critical and quantitative and that the use of LCA requires training. Exactly training in quantitative sustainability assessment is something DTU Civil Engineering has prioritized for a number of years.

"For engineers an important task is to optimize systems and get them to perform in the best possible way. For DTU, it is obvious to work with sustainability in a way which can make sustainability performance quantitative and thereby optimize it, "says Morten Birkved.

Morten Birkved also points out that the concept of "Design for Disassembly" incorporates sustainability in building design in a way that hits directly into several UN sustainability goals, which among others include focus on promoting sustainable industrialization and to call for innovation.

Cooperation across departments provide better solutions

Sara Diraoui and Leonora Charlotte Malabi Larsen's thesis is supervised by Morten Birkved from DTU Management Engineering and Arne Egerup from DTU Civil Engineering. In addition, Harpa Birgisdottir from the Danish Building Research Institute (SBi) has worked as external supervisor on the thesis.

It is precisely collaboration across disciplines and institutions that creates strength in a thesis like this one, says Morten Birkved.

"As a supervisor, I have gotten expert knowledge in building design, which I otherwise would not have gotten, and the students have been able to combine LCA with their civil engineering and building design professionalism. You get the opportunity to create a unique product, when you look at the bigger picture and combine several different disciplines at a high level, "concludes Morning Birkved.

Master's thesis defence on 16 August: ”Design for Disassembly – Building a circular future”

Sara Diraoui and Leonora Charlotte Malabi Larsen are defending their master's thesis "Design for Disassembly - Building a circular future" on 16 August at. 10 am. There are a few seats available. If you are interested in participating, please contact Associate Professor Morten Birkved for details.

DTU is considering seeking funding for an industrial PhD in cooperation with MT Højgaard and the Danish Building Research Institute. This industrial PhD would be focusing on developing both economic and environmental potentials from the "Design for Disassembly" concept to apply in the construction industry.