Cities are leading the way in the circular economy transition. But what does it take to become a truly circular city? This series of articles explore the key services that cities need to adapt in order to become fully circular. These include energy, construction, water, food and mobility. This article delves in the challenges associated with designing circularity into urban buildings.

The Importance of Physical Infrastructure in Cities

Humans are increasingly spending up to 90% of their time in buildings. These structures provide shelter from the elements, a stable environment for working, eating, sleeping and socializing and are increasingly shaping the way we live. Yet buildings use more primary energy than any other sector – accounting for roughly 40% of primary energy consumption.

This can broadly be attributed to the failure of the construction sector to adopt a more whole-systems approach to the design, construction, maintenance, operation and after-life use of buildings. Such a linear approach has also led to the stagnation of construction methods, business models and productivity.

What is most worrisome is that in the next 30 years, the number of urban dwellers will expand from 3.6 billion to nearly 7 billion. China alone plans to move 100 million people into cities in the next decade.

This expansion means that 75% of all infrastructure in place by 2050 does not yet exist. Such a colossal level of construction is a feat that is totally unprecedented in human history. The consequences of this – if done unsustainably – could be disastrous on the atmosphere, the environment, natural resource stocks, the economy, and human health and well-being. Therefore, at most, society only has a generation to ensure this building spree fully embraces the core principles of a circular economy.

In order to approach this challenge, we must first optimize the efficiency of existing buildings, and second, design for the future.

Optimizing Existing Buildings

Before we even consider building any new buildings, we should first look at what is already there and try to figure out how more efficiency can be squeezed out of them. There are many ways to increase the efficiency of buildings, including retrofitting them to become more energy efficient and self-reliant for water supply and waste handling. Demand management can also be streamlined to ensure that internal building space, such as offices at night, reaches a maximum utilization rate.

Under-utilization of building space is a huge problem. Philadelphia, for example has 40,000 publicly and privately owned properties sitting empty which cost the city more than $20 million per year to maintain. Unused office space is perhaps the biggest culprit, as offices tend to only be occupied approximately 30% of the time. A company called Liquid Space in the USA, is tapping into this huge resource waste, by connecting up the ever increasing mobile creative class – who do not need a permanent office – with idle office space.

Successful arbitrage of existing market inefficiencies, in this case real estate, sits at the core of the business case for the transition to a circular economy. Other examples of real estate arbitrage include AirBnB, Couchsurfing and Home Swap. There are also a whole host of creative ways to maximize idle space in cities such as meet up and co-working spaces, homeless shelters, night care and pop up arts and fitness events.

Aside from using idle spaces, buildings may also be retrofitted to become much more efficient in their energy consumption, water use and waste production. A number of publicly funded building optimization schemes were recently launched to encourage retrofitting. The City of Portland, Oregon, opted to encourage the city’s builders to go green with its Grey to Green Initiative, which has approved $1.9m in loans to install reduced rainwater runoff roofs. In Philadelphia, on the other hand, the City has adopted a more punitive approach through a new stormwater fee system which charges building owners based on their level of contribution to the pollution problem.

But the prize for the most ambitious retrofit project has to go to the Empire State Building which, in recognition that commercial buildings make up 75% of the total energy demand in cities, re-manufactured all 6,500 of its existing glass units into super insulated windows. This one action tripled the insulation properties of the building and allowed 96% re-use of existing materials and reduced energy bills by $7.5 million in just three years.

One of the fundamental principles of the circular economy, largely adopted through the Cradle to Cradle concept, is that buildings should not just be ‘less bad’ or neutral regarding their impact on the environment, but net positive.


The need for buildings to be net positive rather than less bad. Regenerative Design.

Take for example the Living Laboratory at UBC in Vancouver, which was designed to produce wastewater that is of higher quality than the rain water that was collected from the roof. It also aims to clean the surrounding air using a green wall and generate its energy from renewable sources on site.


The Living Laboratory at UBC, Vancouver. UBC.

Designing for the Future

Optimizing existing buildings only addresses part of the problem. Even with 100% utilized buildings, current cities will not be able to absorb the influx of billions of people in the next few decades. Therefore there is a need to build more buildings, or in some cases, build entire cities from scratch. This is a daunting but excellent opportunity to apply whole systems’ thinking at the city level.

City planners, architects and contractors face difficult decisions surrounding the role each new building may play during its life time. For example, should buildings that last for a hundred years, such as churches or town halls, be favored over buildings designed for short term need of 20 years? The outcome of which depends on a number of variables, such as how flexible the buildings are with regards to accommodating new users and activities over time and how easily the materials can be recovered after use.

Asides from integrating regenerative design into the construction and operation of the buildings, designers should also be designing for re-use. In doing this, they must change their mind-set from ‘build-use-demolish’ to ‘build-use-rebuild.’ They must consider each building as a bank of materials whereby each material is assigned a digital passport.

The pioneering Horizon2020 funded project ‘Buildings As Material Banks’ was set up to look at just this problem and has the ambitious aim of enabling a systemic shift in the building sector by creating circular solutions. The project, which includes 16 partners from 8 European countries, looks at a number of aspects such as material passports, reversible building design and new business models.

A number of disruptive technologies are enabling the transition to designing buildings and material banks such as Building Information Modelling (BIM) and Radio Frequency Identification (RFID) devices.

BIM effectively creates a detailed digital 3D model of a building which provides a whole manner of information such as the location, size and composition every material in the building. The ownership of the model is passed from architect to contractor to owner and to any future owner allowing operation, de-commissioning and retrofitting much more efficient and viable.


Example of BIM model. National Broadcasting.

RFID technology allows information to be read, without contact, on tags that can be attached to all the individual material components that make up a building. As a result it becomes possible to tack and trace individual items throughout every stage in the buildings lifecycle. The combination of BIM with RFID devices opens a new door to the development of material banks.

Aside from design for reuse, there is also a need to close the loop for unavoidable waste arising from construction or demolition. The South African based company Use-It aims to do just that by re-using waste soils and rubble, that would otherwise go to landfill, to make environmentally friendly bricks to meet the demand for affordable housing. Their success was even recognized this year at the prestigious Circulars Awards hosted by the World Economic Forum.

Making bricks from waste construction soil. Rambrick

The trick to scaling up circularity from the individual building to the city level is to conceptualize a city as a system of physical stocks and flows. Whereby the stocks are the materials currently held in material banks (or buildings) and flows are the re-use of building materials from decommissioned material banks.

By leveraging information gleamed from technologies such as BIM and RFID, a multi-stakeholder collaboration between the likes of city municipalities, the construction and waste industries, building owners, innovation agencies and universities can effectively begin to map the flow of construction resources throughout a city. Such collaboration would offer the ability for all involved to anticipate the availability of resources in the future, hence vastly increasing the ability to become more self-sufficient and circular.