Sustainability is a major focus for many when designing glazing systems and building facades. However, end-of-life reclamation isn’t always considered. In a Facade Tectonics Institute’s 2020 World Congress presentation titled, “End-of-Life Challenges in Facade Design: A Disassembly Framework for Assessing the Environmental Reclamation Potential of Facades,” Rebecca Hartwell, a PhD Candidate at the University of Cambridge, proposed some solutions.
Hartwell explained that end of life is often missed in early design decisions. Metals are recycled frequently but glass ends up as material for roads at best, which is a much lower value than when it went into the building. She also said the problem could be getting worse as old systems were more simplistic.
“We must lower the input of embodied carbon going into the façade system as a whole,” said Hartwell. “… We need to make sure we design for disassembly.”
She explained that the circular economy principle could be applied to the built environment. The first phase, the environmental phase, involves creating an assessment for evaluating the re-use capacity of designs based on the original design and the service life. The behavioral stage of the cycle includes providing an overview of key influences to advance circular economy principles in façade design. The technological step involves creating methods for existing designs such as matching each design to the best recovery strategy and optimizing separation methods. It also involves adapting new design for disassembly such as re-designing laminated glass, creating reversible adhesion and re-purposing products. That eventually leads to the economic phase, which involves creating new business models.
Hartwell has proposed a framework to evaluate reclamation potential. It starts with looking at the material types and quantities and identifying their environmental impact coefficients to define the initial embodied carbon of the system. The next step is to look at the construction drawings to figure out which components are used and their service lives. That information can be used to create a connection diagram which shows how different parts are connected and whether they are permanent or reversible. That can determine the service life of sub-assemblies. Hartwell says it’s also important to factor compromised function into an assembly’s reclamation potential. The next step of the framework is to evaluate the percentage recovery of materials for each recovery scenario before evaluating the residual value in terms of reclaimed carbon for each recovery scenario, as a function of service life.
Hartwell explained that, in a curtainwall system, if a component with a shorter life span is connected with a product with a longer life span, the product with the longer span is now bound to that shorter life.
She gave an example of four possible recovery scenarios:
- Deconstruct and system re-use: Remove the system for re-use, perform any necessary reconditioning and there is direct re-use of a façade unit in a new building.
- Deconstruct and component re-use: Disassemble/separate components, metal components are re-used in a new system and the glass is re-used in a new system.
- Demolition and recycle: Parts are recycled, metal components go to a recycling facility and glass components become road aggregate.
- Demolition: The façade becomes mixed rubble for a landfill and/or incineration.
Her framework also involves calculating the probability of failure and degradation during a system’s design life to determine the percentage chance of a system such as an insulating glass unit operating normally beyond its intended service life. Allowing the system to operate in a compromised state beyond its intended service life is one way to improve its reclamation potential, as the product will have found a second use.
The 2020 World Congress runs through Thursday, August 27 with sessions on Wednesdays and Thursdays. Stay tuned to USGNN™ for our continuing event coverage throughout the month.