“…some walls are essential: they provide structure… others are less substantial: they divide space… the former is seemingly as stable as the human need for shelter; the latter as changeable as our forms of interaction…” ¹

So begins the chapter on ‘the wall’ in the encyclopedic work Elements of Architecture by Rem Koolhaas and his extensive team which includes, among others, thinktank AMO and two Harvard GSD studios. Within this comprehensive exploration of the history and future of walls lies Harvard student Nick Potts’ research. Whereas walls are generally considered icons of stability, since the era of modernism and beyond, interior walls have evolved from being assumedly permanent structures to temporary support systems made of metal rods covered with a thin layer of plaster. Potts sought to illustrate this shift by investigating the replacement of interior walls in Mies van der Rohe’s Seagram Building over time. To do so, he attempted to reconstruct all the floor plan changes the building had seen over its lifetime. Following a significant bureaucratic ordeal, the NY planning department provided data from planning permission documents records showing all the interventions made on the floors over a 23 year period (1990-2013). While absolute numbers where not fully recorded, it nevertheless showed that it can be assumed that within this time frame alone, a minimum of almost 17km of gypsum boards passed through the iconic travertine lobby.² Enough plasterboard to theoretically build several more Seagram buildings. This exercise offers a glimpse of how profound the impact and scale of interiors are. Not to mention the amount of doors, glass panels, flooring, lighting, ceiling tiles, desks, conference tables, cabinets, and service counters that were replaced.

The Interior of a building is closely intertwined with the building’s architecture. It serves as a significant lens through which users perceive the structure from within, connecting their experience with the broader architectural framework. The interplay between volumes, circulation, applied material finishes, and built-in furniture articulates the larger vision of the architecture. 

Simultaneously, the interior operates as an autonomous domain, adapting to evolving ownership, function, and user requirements. The fact that interiors are utilized to reflect changing fashion trends and aesthetic shifts inherently makes them more ephemeral than the buildings themselves; interiors often exhibit a shorter lifespan compared to the building as a whole.

Many architects maintain an ambiguous relationship with interior design, a sentiment echoed in Koolhaas’s aforementioned quote. To them, the building is a structural addition to the urban landscape which is essential to people as it provides shelter. The interior is… well, “less substantial.” This perspective is sometimes taken even further, with some architects expressing disdain for interior design, likening it to mere set design or styling. This characterization not only overlooks the multifaceted and multidisciplinary nature of the profession, but also neglects the essential aspect of meeting the user’s needs. After all, regardless of whether the user’s interaction is subject to constant change, it is as essential to the viability of a building as the building’s construction. 

Perhaps architects’ unease toward interiors stems from a lack of control. The complexity of stakeholder’s involvement and the structuring of the design process in a building limit the architect’s influence on interior design. This is especially true when tasks are divided between building architects and interior architects, who work on the project in different phases. This division can lead to certain finishes being reversed halfway through, or the imposition of conditions on the interior that influence its performance. A greater synergy between interior design and architecture, coupled with mutual respect, leads to interiors that offer enhanced performance over a more extended period while generating less waste. Nonetheless, even in such cases, as time progresses, the architect’s sphere of influence diminishes, while the user’s sphere of influence expands, eventually making the interior a standalone component.

The greater systematic downplaying of the relevance of interior design means that research on interior design is also less developed. And because the exact environmental impact of interior design is unknown and underestimated – the Seagram Building example is anecdotal – it is most often omitted from national or international policy that guides the transition to a circular construction economy. Additionally, interior designers tend to have less organized communities compared to architects and currently wield less influence on the political stage.

From a sustainability perspective, the rapid sequential execution of interior design is undeniably problematic and warrants thorough consideration to assess and mitigate its environmental impact. The Shearing Layer diagram by Brand and Duffy (page XXX), often cited in circular design discussions, proves inadequate in its classification of interior categories, with unsubstantiated timescales attached to each category. Importantly, the lifespan of interiors varies significantly based on their typology, such as less context-bound, and rapidly changing designs for retail, hospitality, and exhibition design versus office, school or healthcare interiors that are more interwoven with the layout of the building. What truly matters is the lifespan of materials and elements and their alignment with the longest possible duration without degradation. In this regard, interior design follows the same circular principles as architecture, with a focus on designs for disassembly, modularity, waste minimization, reusing, recycling, and securing material data. This guide will cover all of these aspects in detail, emphasizing that the starting point is the main distinction.

Getting started

Why a guide? 

There is no lack of publications and websites offering circular design methodologies. Most of them, however, will always take the building as their point of departure, and the interior remains an afterthought, at best. Starting from the interior reveals more fundamental and significant challenges that need to be addressed if we are to have a really circular building economy. Not only is the aforementioned turnaround time of projects much shorter, but the design process is different as well. There are often fewer stakeholders involved, which leads to less knowledge exchange within a larger community. Project budgets are also smaller and high time pressure make it difficult to avoid resorting to existing patterns or solutions. There are also some aspects that are simply less feasible in shorter design cycles. It takes time to source the right materials for successful reuse. If materials are not immediately available, i.e. by harvesting them from an earlier project, it often proves impossible to find them given the limited time frame of a project. This is partly because the current markets for reused building materials are different for interior construction and generally underdeveloped. Another significant obstacle is that circular architecture relies heavily on software solutions, such as BIM or Revit, which make tracking material usage easier, but those programs are usually not used in interior design as they are overly elaborate and too time-consuming in the design process. 

How does this guide work? 

At the heart of this guide are three circular interiors which having been realized are taken as case studies. All stakeholders, from the client, to consultants, designers, architects, builders, and demolishers, were interviewed regarding their role in the project, the challenges they faced, and the solutions they found. The connecting tissue between the case studies is formed by a number of contributor essays, starting with some of the circular design basics for those new to circular design. This introduction frames a larger context of precedents, the urgency of transitioning, and where we are. This is followed by a section that looks more closely at specific methods, such as life-cycle analysis, marketing, and material innovations. And finally, the guide also offers a larger meta-commentary on the structural learnings that were revealed in looking at the life-span thinking in design, cleaning, and maintenance, and the importance of rethinking the esthetical framework within design. 

Why the Netherlands? 

Not only are the three case studies in this not-so-easy-guide all based in the Netherlands, also the essay texts are largely rooted in (North-West) Europe. This makes the Netherlands itself the case on which this guide is founded. This does not imply that the knowledge and projects presented are unprecedented; for all of them an equivalent can be found elsewhere. The Netherlands was chosen for the availability of the network to execute this extensive and detailed survey. As a country, it can also be considered a relatively probable environment for implementing circular economy principles. A high level of consumption leads to a relatively large share of the global footprint, which makes it necessary for the Netherlands to take responsibility. The high prosperity, well-educated population, and broadly developed building culture offers, in principle, sufficient (economic) resources for investing in innovation and rolling out new policies. In addition, it is tied into larger extranational systems of the European Union, amongst others, which are increasingly demanding sustainable development. 

And why these specific cases? 

The guide provides insight into the unruly practice of circular building in a linear world through each of the case studies and the different ways in which obstacles have been overcome within them. For this purpose, it uses different typologies such as museums, schools, and offices. The listing is far from complete, but together, the selected projects show the large differences in circular dynamics within which interiors are designed. The projects each have their own complexities, other investment backgrounds (public or commercial), and depreciation terms, certificates, or additional requirements belonging to their specific typology. Together, they stretch the concept of interiors and what it includes.

What they share is great ambition on the part of all involved to reject greenwashing and live up to the circular aspirations, not least with the backing of an engaged client. Just as with major architectural projects, nothing is possible without a commissioner willing to experiment. There is still much talk in the building sector about whether or not circular building is more expensive and whether it is necessary to make concessions on design or compromise on certain comforts or quality. Much of this will likely change as the world moves further toward a circular economy, but for now it takes courage and commitment from the commissioner to fully engage in this process.

The cases have been selected for being the ‘top of the crop’ in both their ambition and execution. However, they may not represent the most experimental in their development or have the most spectacular result. They were intentionally selected as non-niche projects to demonstrate that circularity is achievable on a broader scale, catering to a wider audience.

¹Elements of Architecture (2018, Taschen), p.89.

²Ibid., p.171-178.