Office retrofits: Three key hurdles in renovating commercial buildings

The upcoming UK Net Zero Carbon Buildings Standard is expected to align with the operational and embodied carbon performance levels needed to meet the 2030-35 Paris-proof targets.

Several organisations, including the UKGBC and BCO, have acknowledged that very few retrofit office schemes meet these targets, with the average upfront embodied carbon more than double the 2030-35 interim target. How can we enable a responsible retrofit, one that respects existing buildings while delivering a sustainable long-term solution?

Retrofitting commercial office buildings is the only way to meet these requirements and ensure the properties can continue to be let, due to the requirement of an EPC rating of B or above. Greater power rests with building design to influence and drive change and reduce whole-life carbon emissions, but it requires a shared vision across the industry.

It is widely recognised that significant fabric improvements are needed, in addition to services upgrades, to reach higher levels of long-term asset performance. To make retrofits financially viable, it is often the case that new-build additions are added to existing buildings.

What is often glaringly obvious (to specialists) as the lowest-carbon or most materially efficient approach is not always the preferred redevelopment solution. This is usually justified on two grounds: first, the return on investment; and secondly, technical limitations in delivering the GIA ‘required’.

As a result, typical major retrofits often propose a proportion of demolition – either to reposition the existing core to allow for re-organising the existing grid for better let-ability, or to make structural redesigns to accommodate the new massing and increase floor-to-ceiling heights. The level of interventions needed to deliver the desired scheme (i.e. to be seen by the market as equal to a new-build office) often has a very high embodied carbon impact.

Exploratory stages dictate how much of the existing could be incorporated within the proposed scheme

It all starts with the client brief. A design team responds to this brief, by developing a range of massing options against several performance criteria for offices. These initial exploratory stages dictate the pathway in deciding how much of the existing structure, finishes and services could be incorporated within the proposed scheme.

Not all existing buildings can meet a lettings agent's spatial preference for a speculative office and re-designed existing buildings are expected to meet, or compare to, new-build criteria to make them commercially successful. For example, the BCO Guide for Offices (2019) recommends a 2.6m to 2.8m height from the finished floor to the lowest exposed services in the ceiling, for a typical new build. The guide states a relaxed height range of 2.45m to 2.8m for refurbishment.

However, the agent's feedback of ‘poor rental income from lower-ceilinged offices’ discourages clients from considering retaining these spaces. Typically, a client brief requires for a finished floor-to-ceiling height to be closer to a new-build equivalent, directly impacting the design approach from the project team.

Another key factor that influences the scale of demolition in a scheme is the location of the core in relation to the proposed structural grids to allow easy sub-division of spaces. A central core typically offers more efficiency in access to facilities required for multiple tenants.

These two scenarios alone can easily result in 50 per cent demolition of the existing structure and added carbon from the new build, irrespective of the increased overall GIA of the proposed scheme.

It is common to strip out the existing internal fit-out to avoid paying business rates

It is also common, on schemes that are going through major refurbishments, to strip out the existing internal fit-out to avoid paying business rates while the redevelopment gets planning approval. When this happens, the opportunity to enable reuse within the scheme is lost before the design team can even engage with the existing materials. One can’t help but then wonder if the point of adding up carbon for the new build and fit-out is just for ‘reporting’, rather than to strategically influence the right direction of travel in addressing the climate emergency.

This attitude of removing the existing and replacing with ‘low-carbon’ new build should be challenged. A responsible demolition and strip-out is integral to reducing not only the embodied carbon, but also the embodied ecological impact arising as a result of development.

Clients need to encourage their project teams to directly engage and challenge the agents’ assumptions on rental model and the level of Cat A fit-out that is needed. This, combined with early market engagement, can enable a lower-impact retrofit strategy.

Project programmes need to allow for longer early stages

Project programmes also need to allow for longer early stages, so that surveys can gain deeper understanding of the existing building and give the design team time to arrive at the right solution. But all of this will have an impact on consultants’ fees for retrofits.

On the plus side, informed tenants are shifting their mindset to be more respectful of existing buildings, and also expecting base builds to be of higher quality. There are numerous emerging examples of how project teams are driving change through high retention of existing elements, lean extensions, as well as incorporation of reused components (steel, MEP equipment).

Our own experience from The Entopia Building (in Cambridge) and The Rylands Building (in Manchester), shows that it is possible to deliver successful retrofits if there is better collaboration with the supply chain. What was thought to be ‘not the standard approach’ was possible on both of these projects in terms of operational energy, embodied carbon and material reuse.

No one retrofit solution fits all buildings. We are all custodians of the buildings we work on, and the design responses should continue to celebrate the existing, as well as deliver desirable future workspaces for occupants.