Each month, PTE's Knowledge Hub team will explore the complexities and technical challenges British project architects face every day.

‘To retrofit, or not.’ Let’s be honest, that’s the question we’re all asking today. If only there was an easy answer. But when every site is like a bespoke suit, a yes or no answer is going to be hard to land upon. It got me thinking… what if there was a failsafe tool that could calculate whether the end-users, clients, and people who have to live with a proposed site development, would be better off with a newbuild or a retrofit of what’s already there on site?

When clients need to make that decision, it can open a minefield of conflicting views and metrics.

Before I continue, I should explain what I mean by ‘retrofit’. In construction, retrofitting means making improvements to an existing building by adding new systems, materials, or technologies. The goal is to boost the building’s performance, efficiency, or function. These changes weren’t part of the original design and can be as simple as better insulation or as involved as replacing heating and cooling systems.

Some say retrofit wouldn’t be needed if building owners had carried our regular maintenance and upgrades. Regardless, we have a building stock still functioning as if energy were a cheap commodity. So, what happens when clients have to make a retrofit judgement call? Some argue that unless you’re actively converting commercial building into homes, retrofitting existing stock doesn’t expand housing supply. If you’re on a housing waiting list or in an overcrowded home, retrofit may not be your priority. Others argue that it is a sustainable and efficient method of providing homes fit for the future. If you have a spacious but damp maisonette, you might not support a decade-long estate regeneration but would welcome a minimally disruptive home upgrade.

Clients must also consult housing managers, maintenance, valuations, funders, and meet their local housing and community needs. Achieving consensus among so many stakeholders with diverse views can be impossible. As architects, when assessing new opportunities, we use a consistent, scored method to ensure sound decisions - while allowing for subjectivity when needed.

Could a ‘go/no go’ approach work for retrofit decisions? It would bring due diligence to choices that are often emotional and far-reaching.

Cressingham Gardens in Lambeth shows what happens when decisions lack transparency. Lambeth declared retrofit financially unviable - but did they weigh other options or consider impacts on residents and the neighbourhood? An open ‘go/no go’ process might have eased hostility and led to a better outcome for all.

Why not go further - a national ‘go/no go’ for retrofit? While it would need to address regional differences, it isn’t impossible.