Adaptable housing

Physical Demonstrator

City context

In Copenhagen, new residential buildings tend to be designed to the same specifications. In fact, 66% of apartments have three rooms and the floor area of the flat is between 85–115m², not including outside areas such as storage space, a balcony, etc.

Currently, prefabricated concrete construction with loadbearing walls are the norm in Danish construction. In this approach, structural concrete elements are cast together to form internal and external walls and floor slabs. However, this limits flexibility, both horizontally and vertically, and the structural elements are difficult to modify without major interventions. Services like underfloor heating, drainage and electricity are often integrated into the concrete. This makes them difficult to access for maintenance or replacement without demolishing part of the structure.

Projections show an increasing need for smaller one and two-room apartments in Copenhagen. But because of the way Danish buildings are currently constructed, it’s unlikely a simple layout shift alone could meet future demands. This means buildings are at risk of being prematurely demolished in favour of new dwellings.

DfD and DfA approach

The adaptable housing demonstration project in Copenhagen aimed to show how apartment blocks that use DfD and DfA principles could meet future housing demand and deliver significant environmental and economic benefits.

The demonstrator showcased an alternative structural system based on frame construction. It included a frame system without loadbearing walls. Slabs could be removed to significantly increase adaptability, both horizontally and vertically.

In addition, including mechanical fixings and lime mortar instead of cement allowed components to be dismantled. Design enabling disassembly of building layers, avoiding cast-in services and replacing concrete screed with sand enabled services to be replaced or maintained easily without major interventions.

The demonstrator also included standard prefabricated elements such as concrete columns, concrete core, steel beams and hollow core slabs.

Key findings

Compared to a business as usual (BAU) case study, the DfD and DfA approach had a substantially higher reuse potential (85%).

Results also indicated that the embodied carbon of the BAU approach and the DfD and DfA approach were almost the same after a single building lifecycle. However, if the DfD and DfA buildings were redeveloped, there would be an embodied carbon saving of 37% after the first redevelopment and 50% after the second.

Constructing the alternative buildings and disassembling them would be 25–28% more expensive than using the BAU approach and demolition. However, if the alternative buildings were redeveloped, there would be a 27% cost saving after the first development, and 45% after the second.

Adopting DfD and DfA principles may require a higher upfront investment, but by extending the lifecycle of a building and its elements, there can be substantial environmental and economic benefits after just one redevelopment.

The Klassenhäuser structure – slab construction

Physical Demonstrator

City context

In Hamburg, several schools were built using comparable design concepts. This demonstrator aimed to compare the impact of conventional construction floor slabs against three DfD versions.

DfD and DfA approach

The BAU case for this design was a conventional floor slab made using an in-situ concrete method. Three different types of DfD floor slabs were made using pre-stressed concrete cast elements, pre-stressed concrete cast elements with seam and joint and a bolted timber-concrete construction method to aid disassembly and reuse.

Key Findings

The demonstrator found that the DfD slabs could be dismantled completely and sorted by material type. The DfD floor slabs used 40% less concrete, representing significant material savings and associated carbon impacts. Additionally, the DfD slabs interlocked, which meant, unlike traditional methods, no gaps needed to be sealed.

Using the pre-stressed concrete slab with seam and joint did result in dimensional differences. The DfD school building was 50cm higher than the comparable BAU building, which affected wall heights, staircase and railing lengths, pipe lengths and the distance between the building’s columns. These had to be reduced, resulting in more columns and fewer open spaces, which is a drawback that would need to be considered when weighing up the benefits of using this method.

Overall, the demonstrator showed that using DfD slabs could lead to a 70% cost saving over multiple lifecycles of the building, as well as significant carbon savings.

Design for disassembly warehouse

Virtual Demonstrator

City context

Traditionally, warehouses are designed to remain in a fixed location, be in use for around 20–40 years, then demolished, typically a long time before their technical lifespan is complete. Demolition is more likely to occur because of economic redundancy than technical limitations.

DfD and DfA approach

A single-storey steel framed DfD warehouse was designed that could be dismantled and reused in another location. The warehouse used demountable concrete foundations to allow for disassembly. All connections in the steel and concrete structure were bolted. The columns were also given the option of variable heights, allowing the warehouse hall to be either 5 metres or 3 metres tall. This DfD warehouse was then compared to a conventionally built warehouse in terms of environmental and economic impact.

Key findings

Almost 100% of the DfD warehouse materials could be reused or recycled at the end of life.

Lifecycle assessment (LCA) calculations showed that over three lifecycles (relocating the DfD warehouse compared to building a new conventional warehouse) there were carbon savings of around 40%. Over two lifecycles, calculations showed that the DfD warehouse had significant cost savings, and over three lifecycles the cost saving was 41%.

Overall, it was found that applying DfD methodologies to a warehouse can be challenging because of compliance with regulations for factors such as loads, fire class and building purpose. This challenge should be taken into account in the early stages of DfD design.

Albion Street (The Hithe) – Flexible temporary building

Physical Demonstrator

City context

In London, some local authorities have small parcels of centrally located but underused land that currently only host low-value uses such as storage. To trial new uses for the space, ‘meanwhile use’ construction can be valuable to provide amenities for residents.

DfD and DfA approach

A two-storey affordable office building was designed and constructed using DfD and DfA principles. The building was intended to be disassembled and relocated after 10 years, due to the lease terms for the land it was built on.

The DfD and DfA design was compared against a BAU case study in terms of its environmental and economic impact. A key difference between the two designs was that the DfD and DfA design used modular demountable structural insulated panels (SIP). The BAU design used a traditional steel frame with low-tech timber rainscreen cladding.

Key findings

The economic impact assessment found that the DfD and DfA approach resulted in a 6% increase in construction cost compared to the BAU approach. However, there was a 23% reduction in overall whole life costs.

The results of the LCA study showed an initial 6% increase in whole-life embodied carbon over the BAU base case after the initial construction and use cycle. After the first redevelopment cycle, there was a 30% overall saving in whole-life embodied carbon against the BAU case study. After the second redevelopment cycle, this increased to an overall saving of 46%.

The demonstrator showed that its lifetime could be prolonged by at least 30 years. This was a 200% increase over the BAU case study. It is based on a functional need (use cycle) of 10 years and an ability to accommodate at least two additional use cycles.

The demonstrator targeted a 100% demountable design. However, general wear and tear will likely lead to replacement of materials in a redevelopment. Therefore, a waste allowance of 5% loss during disassembly and 5% loss due to wear and tear was assumed. This means 90% of the building elements for the DfD and DfA approach are estimated to be demountable/reusable.

Develop principles and tools for implementing DfD and DfA in social housing

Step 1 – Outline a ‘cost pyramid’ of use cases that could deliver DfD and DfA in social housing

Use cases outlined a specific situation in which DfD and DfA approaches could add value. These use cases could then be classified in a ‘cost pyramid’ ranked with cost neutral uses cases at the bottom to more expensive ones at the top. Professionals could then decide which to use, depending on the project.

Step 2 – Develop design criteria and tools for DfD and DfA in social housing

These included guidance on DfA and DfD integration in maintenance plans for social housing and structural, fire and acoustic impact and considerations.

Step 3 – Develop procurement criteria and tools for DfD and DfA in social housing

Circular procurement guidelines have been developed in Denmark. The criteria focuses on a specific percentage target by weight for DfA. Project teams were invited to propose solutions to achieve that target within the budget.

Develop and agree on financial models and incentives for DfD and DfA in social housing

Step 1 – Agree methodology to integrate DfA and DfD in lifecycle costing (LCC)

All social housing in Copenhagen requires a lifecycle cost analysis. But this doesn’t cover factors like reuse and adaptability as ways to reduce costs for a building’s lifecycle. As a result, a new methodology should be developed covering elements like deconstruction, transportation and adaptation costs.

Step 2 – Investigate integration of LCC in budget allocation and funding for social housing

Budget allocation for social housing is based on a fixed upfront cost, plus a fixed percentage to cover future maintenance and replacement. There’s currently no way to increase budget for upfront costs, even if it means savings over the life of the building. Changing this is complex and requires a specialist group to influence funding.

Step 3 – Develop circular financial models for social housing

Based on use cases, there’s huge potential to develop new circular financial models for social housing. This could include portfolio-based renovation strategies with material flows between assets. Once tools are in place, financial models should be developed by social housing developers and promoted by Copenhagen Municipality.

Create a city strategy to support DfD and DfA in social housing

It is crucial that the city of Copenhagen communicates its ambitions relating to circularity in housing to inspire change in the industry. A city strategy can help achieve this.

Step 1 – Create and promote a vision for DfD and DfA in social housing

As part of the city vision, it is suggested to include targets for DfD and DfA amongst new construction and for the city to also develop ‘future use’ scenarios of development areas which might see a change of use in the coming 50-100 years.

Step 2 – Develop pilot projects and showcase to engage industry

Copenhagen Municipality has the potential to support pilot projects through funding, but also by leading the projects in areas where they are the developer alongside social housing associations. Two areas suitable for pilot projects have been identified: By Strømmen and Gammelby.

Facilitate greater consideration of full building lifecycle

Step 1 – Set direction of travel

Normalise the consideration of disassembly by adjusting terminology in the Housing Pattern Book and, in due course, in the wider industry. Ensure design teams consider circular economy design principles and approaches by requiring the preparation of circular economy statements across Buyers’ Club developments.

Step 2 – Assess the value of circular economy strategies over a building’s lifecycle

Given that councils often hold a long-term interest in sites that they develop, make investment decisions based on lifecycle costing (LCC) in preference to capital cost alone.

Step 3 – Digitise information on assets

Being ‘digital first’ helps make it easier to effectively use and manage building assets through their lifecycle. Tools like material passports (a digital document listing all the materials that are included in a product or construction during its lifecycle) help make DfD and DfA simpler.

Drive appropriate application of circular principles

Step 1 – Design for internal flexibility

Needs of residents and the city’s housing mix may change over time. To improve the chances of buildings continuing to meet housing needs, consider the potential for flexibility in apartment sizes and layouts.

Step 2 – Design for adaptability

Changes to demand on building stock are very difficult to predict. However, measures like extra structural capacity, e.g. allowing storeys to be added, will help buildings to adapt.

Step 3 – Design for disassembly

Designing for disassembly helps maximise the reusability of a building’s components at the end of its lifecycle. Shorter life building elements should be removable and replaceable.

Step 4 – Set key performance indicators (KPIs) at a building level

Include indicators to measure material use, current material end-of-service-life scenarios, intended future material end-of-service-life scenarios and embodied carbon.

Build the capacity to deliver circular MMC

Step 1 – Create comprehensive guidelines for DfD

Build capacity to deliver circular MMC and increase familiarity with design for adaptability and disassembly among design teams and supply chains.

Step 2 – Engage supply chain with the developed KPIs and DfD guidance

The Housing Pattern Book contains a strong section on circularity and DfD. The guidelines provide technical criteria for design teams to apply through the design process and can frame conversations with suppliers.

Step 3 – Standardise more building elements in the Housing Pattern Book

The Housing Pattern Book already proposes standardisation of bathroom pods and utility cupboards, and it lists additional elements with potential for standardisation: cores, risers, façades and balconies.

Based on RightSizer, one of London’s demonstrator projects, floor, ceiling and partitioning systems could also be developed with suppliers to increase internal flexibility, building adaptability and component disassembly. Progressively address standardisation potential of each building element.

I. Local authorities can help to create circular supply chains by driving demand for novel DfD construction by adopting its use in public projects

Strategic: If local authorities take a leading role in briefing design teams to specify DfD, they can reduce embodied carbon emissions in line with their own carbon reduction objectives and help to break down barriers to the wider adoption of novel circular construction.

Financial: Compared to BAU, upfront costs were found to be 25% lower for Demonstrator 25 and 1% higher for Demonstrator 26. Lifecycle cost savings of 37% Demonstrator 25 and 61% Demonstrator 26 were achieved once the components were used for a second time.

Feasibility: Adopting novel construction techniques requires strong impetus from those commissioning construction to set a direction of travel. Officers in development and regeneration roles will need to understand the reasons for the policy and act as custodians as the policy is enacted in project briefs and challenged through the course of a project’s development.

Appointed design teams will be asked to design and specify product systems in a way that differs somewhat from their normal practice. Clarity of rationale and awareness of carbon and circularity will be key to resisting pressure to revert to BAU.

Risk: Association with innovative, circular businesses can enhance the reputation of a local authority amongst staff, residents and industry. The opportunity cost of achieving carbon savings or other environmental benefits should be weighed against other options for achieving the same benefits. The starting point is to understand the scale of benefits. In the demonstrator cases, DfD was found to achieve 75% and 85% reductions in embodied carbon emissions once components were used for a second time.

Scalability: The emergence of building futures contracts and a market mechanism for their exchange will lend credence to the long-term residual value of DfD construction, and justify additional upfront investment.

Nevertheless, the ability to scale this business case depends on the availability of DfD products that are ready to apply to major projects. Greater demand for DfD from across the market, driven by progressive purchasing and tighter regulation of whole life carbon, will create more opportunities for businesses to develop such products.

Related demonstrators: Demonstrator 25 – Hamburger Klassenhäuser – Slab construction, Demonstrator 26 – Hamburger Klassenhäuser – Façade comparison.

W. Manufacturers can generate new revenue streams by developing demountable product-as-a-service business models

Strategic: Manufacturers can retain ownership of assets and generate revenue from leasing building products and systems, including partition systems, façade components, warehouse buildings and raised access flooring.

Financial: In the demonstrator projects on which this case is based, upfront costs were found to be higher where systems were designed for future disassembly (by 11–25%). However, lifecycle cost savings were achieved once the components were used for a second time (13–25% saving), and with each additional use cycle this return on investment improved further.

Whilst future returns are inherently uncertain, the Neustadt case showed real savings achieved for the recipient project through the reuse of 200m² of a partition wall system in collaboration with the original manufacturer. These savings represent a competitive advantage for a manufacturer that is able to disassemble, reassemble and re-warranty their products.

Feasibility: Disassembly and reassembly techniques exist but leasing models remain largely unfamiliar to developers, specifiers and contractors. A shift in mindset is required for these models to become commonplace. Pricing and ownership models need to be considered to suit different component types and market segments.

Risk: There is financial risk in increasing manufacturers’ upfront costs with returns coming over a long period. There is organisational risk for existing manufacturers in developing and integrating new business models where traditional upfront sales models are felt to be effective. However, retaining ownership of materials is a hedge against future resource price rises and price volatility.

Scalability: Leasing models are most applicable to shorter lived building components, temporary buildings and typologies that could be expected to be deployed on different sites before the end of the components’ lifespans. If they become commonplace, it will raise questions over universality/compatibility versus manufacturer-specific technology (e.g. connection types) and subsequently collaboration versus competition amongst manufacturers.

Alignment over technology (e.g. connection types) and robust information retention (e.g. through material passports) will help to ensure that components are disassembled and reused as intended, even if their original manufacturer ceases trading.

Related demonstrators: Demonstrator 27 – Neustadt – Partition walls, Demonstrator 29 – DfD modular façade – Taastrupgård, Demonstrator 32 – DfD warehouse, Demonstrator 36 – Green Street affordable workspace.

E. Public and private developers can create more valuable homes, improve resident satisfaction and reduce lifecycle cost by developing adaptable housing

Strategic: Public and private developers can create more valuable homes, improve resident satisfaction, reduce lifecycle cost and simplify maintenance and upgrades by developing adaptable housing that facilitates multigenerational living and flexibility of living and working.

Financial: In the demonstrator projects on which this case is based, upfront costs were found to be higher where systems were designed for adaptability (by 21–24%). Savings are achieved when dwellings are transformed to suit changing needs, especially where the alternative is demolition and new construction.

In one case, the redevelopment of an adaptable home compared to demolishing and rebuilding after one use cycle resulted in a 28% lifecycle cost saving. Economic benefits for the building owner may also be generated by shortened periods of vacant flats, due to the capability to adapt flats to meet changing demands.

Feasibility: Adaptability can be achieved through simple design changes such as optimising positions of load-bearing elements and building services layouts and accessibility. The demonstrators apply construction methods and technologies that are readily available.

Risk: The resident survey conducted in Helsinki found that there is demand for flat adaptability amongst both owner-occupiers and tenants, as it reduces the likelihood of having to move house, allows changing use of space as family life and work life change, and makes it possible to rent or sell a part of the flat to yield income.

There is a willingness to pay a premium for adaptability, generally 2–10% on top of the purchase price, if its potential benefits are clearly communicated. For building owners, investment in adaptability reduces the risk of buildings being demolished before the end of their technical lifespan.

Scalability: In owner-occupied housing, the investor and the beneficiaries are different. The potential savings must be communicated and recognised as additional value at the point of sale, otherwise the split incentives will reduce motivation to invest in adaptability. For public developers and housing associations that retain ownership of buildings, adopting lifecycle costing is essential to assess the merit of designing for adaptability.

Related demonstrators: Demonstrator 28 – Copenhagen adaptable housing, Demonstrator 33 – Helsinki adaptable flats, Demonstrator 35 – RightSizer

F. Public and private landowners and asset owners can achieve increased rental income by facilitating ‘meanwhile use’ of underused land and assets

Strategic: The term ‘meanwhile use’ represents a range of strategies that can be put into place to make under-utilised spaces and places become productive, both in an economic and social sense.

Landowners can achieve increased rental income by identifying opportunities for ‘meanwhile use’ and maximising use of land and assets prior to longer term redevelopment.

Financial: Land and assets earmarked for redevelopment are often protected with hoarding and security services in the period before construction starts. These periods of under-utilisation of assets are often significantly longer than is first anticipated, potentially leading to years of outgoings.

Meanwhile use’ achieves rental income and avoids the need to pay for securing disused sites, but it requires investment in a temporary building (by the landowner or others) that may need to be deployed multiple times to achieve a return. The demonstrator on which this case is based was a disused brownfield site. Upfront construction costs of a relocatable building to suit a 10-year lease period on the site were found to be 6% higher than an equivalent building not designed to be relocatable. However, lifecycle costs for three 10-year uses of the building were 23% lower.

Feasibility: Information about a site’s previous use allows assessment of the capacity of any existing foundations. In the demonstrator case, the ‘meanwhile building’ was designed to be lighter than the previous building so that no new foundations were required. The demonstrator used standard construction materials and techniques, with some modifications to improve design life and demountability.

Construction supply chains are not fully prepared to scale these techniques to maximise their potential impact, but the supply capacity and skills required are within reach. Deconstruction and relocation expertise exists, but it will also need to be scaled to meet the needs of a larger market in relocatable buildings.

Risk: Maximising return on investment will require ‘meanwhile buildings’ to be deployed multiple times. Under current regulations, a building will be defined as new at the point that it is relocated to another site. It will require full planning permission and will need to meet the relevant building regulations of the day. This may add complexity and cost to future relocation.

Scalability: All buildings become non-compliant over time, but existing buildings that remain on the same site do not need to be recertified every 10 years. This raises the question – Should relocatable buildings become a new special category and regulations relaxed to simplify their widespread adoption?

Taking London as an example, there are 466 disused plots of land of a size that would be suitable for ‘meanwhile use’ similar to that adopted by Demonstrator 34. The total area of this land is nearly 500,000m². In the UK as a whole, there are 36,000 disused brownfield sites. This represents a significant opportunity to roll out ‘meanwhile use’ prior to redevelopment.

Related demonstrators: Demonstrator 34 – Albion Street / The Hithe