Kære Frank Jensen,
AKT II commend the initiatives of the Copenhagen 2025 Climate Plan, however understand that there is a significant gap to be filled in order to achieve these goals. Currently around 10% of global CO2 emissions are due to the production of steel and cement alone (around 4400M tonnes of CO2)1. Also a disproportionate 27% of waste in Denmark originates from renovations and demolition carried out by the construction industry only<footnote>2<footnote>.
AKT II are now taking urgent action to tackle ‘upfront carbon’, as well as designing with the whole life of a building in mind. We are carrying out ‘Carbon assessments’ at each key design stage through to practical completion, with the aim to optimise carbon reductions in our projects. We would like to focus here on two initiatives that help to provide effective tools in reducing the carbon emissions of our projectsRe: retention and re-adaptive reuse of the existing structure and fabric, and reduction of the embodied carbons in new structural designs using materials with lower carbon footprints. We believe adopting these initiatives can help to positively contribute to the current and future development of Copenhagen, in light of the climate emergency and the CPH 2025 climate plan.
Reuse & Adaptive Reuse
The most effective way of reducing the embodied carbon of a development is reusing the structure of building stock that already exists.
The technological boom of the last two decades has not only changed the nature of work and how we ‘use’ buildings, but has also given us the tools to forensically inspect what has occurred before, while looking for opportunities to successfully and efficiently reuse and adapt existing building stock. Inherently designing in flexibility to new buildings should become standard too, but creating flexible and robust designs for future use in existing building stock should also be a key aim.
Examples of some related project tools to focus on here, that should become standard to ensure robust future developments, are:
•• life-cycle analysis; calculating the environmental impact of a building across its whole life-cycle
•• life-cycle layering; designing for disassembly plus designing different components of buildings (structure, facades, ventilation systems etc) for different design-lives to optimise robustness and relevance of a building throughout its life-cycle, and
•• building or material passports: ensuring a quantifiable list of building components and/or materials with their end-of-life recovery potential clearly stated.
Construct in Timber
Material selection for either a new or adaptive reuse project is key to ensuring the embodied carbon of the development is optimised. Whilst not always the right solution for a project, timber construction methods and materials such as cross laminated timber (CLT) can provide gains in both the embodied carbon of a structure, and diminish the impact of construction through reduced construction transport requirements and construction programme times. For example, a CLT structure can take around 20% of the total construction site delivery trips required for a similar pre-cast concrete framed project.
The figure to the left shows a comparison of embodied carbon, by structural material/scheme, for a recent o ce building project. It was shown to be feasible for a hybrid steel and CLT frame to be carbon negative.
Furthermore, the inherent lightness of timber as a material means it is an invaluable tool for ensuring the success of an adaptive reuse project.
We hope that these initiatives can help to provide a basis for ensuring the successful and sustainable future development of Copenhagen. We are available to discuss the items in this letter with you should you wish to explore them further.
Med venlig hilsen,
Ed Durie, AKT II København Consulting Structural and Civil Engineers
1. Moynihan, M. Held to Carbon Account. The Structural Engineer, January 2020.
2. Circle House Lab. Green Paper 02. Circle House Lab, 2020.