RETROFIT THE WHOLE BUILDING

At Specify & Build’s recent retrofit round table, experts argued that successful retrofit needs to begin with the building itself, with a long-term plan for how every intervention will work together.

Heat pumps, insulation, roofing, windows, solar and other technologies all have a role to play in improving existing buildings. But are we making the most of the energy efficiency benefits that retrofit can bring, and taking a holistic approach to upgrading buildings?

Imagine spending thousands of pounds installing solar panels on a school, only to discover that the roof beneath them is nearing the end of its life. Or investing in a highly efficient heat pump that struggles to deliver affordable warmth because the building itself is losing heat faster than the system can replace it. These hypothetical scenarios reflect the kinds of problems encountered by the architects and specifiers who took part in our recent retrofit round table, and point to a fundamental weakness in the way the UK improves its existing buildings.

With enormous pressure to decarbonise the built environment, the industry has become very good at promoting individual solutions. But a better product doesn’t automatically mean a better building. For the architects, consultants and manufacturers around the table, the message was clear: successful retrofit is not about installing as many energy-saving technologies as possible. It’s about understanding the building, knowing what needs to be achieved and making certain every intervention contributes to that outcome.

“We never get asked to look at the roof before someone’s done the windows,” one participant told the group.

He described working across large estates where roofs were surveyed and graded to establish how improvements would affect windows, services and other building elements. Yet he has repeatedly encountered schools where extensive solar PV arrays had been installed without addressing the roof beneath them.

“You’ve got solar energy, but the heat is just disappearing through the roof and windows. Specialists need to get together at the beginning of the project, and that doesn’t seem to happen.”

The problem is partly structural. Retrofit projects are frequently organised around individual measures because that is how funding and supply chains operate. Clients commission solar panels, windows or heating systems, often before anyone has assessed the building as a whole.

UNDERSTANDING PERFORMANCE

Several delegates said the answer begins with understanding how a building performs before deciding what upgrades to make. One consultant described clients approaching specialists with a general desire to improve their property but without an energy model or clear plan. His preference was to model the building, test potential interventions and establish what different product combinations could achieve when working together. Rather than asking which heat pump, insulation system or window performs best on paper, the question becomes which combination is appropriate for the building, its occupants and the client’s objectives.

Another delegate described this as the difference between a “whole system approach” and a “component approach”. There is no ‘one-size-fits-all’ retrofit solution that works properly with every property. The right solution depends on the building’s condition, use and future requirements, and how the different building components interact.

PLAN FOR THE NEXT 10 YEARS

One idea that attracted particularly strong support was the concept of a building passport, or whole-building retrofit plan. The principle is straightforward: assess the building, establish its intended future performance and develop a sensible sequence of improvements that can be delivered over time. This doesn’t mean every property needs an expensive deep retrofit to be carried out all in one go. Instead, improvements can be scheduled as budgets permit or when components reach the end of their useful lives, without compromising subsequent work.

For example, a homeowner with £50,000 available annually doesn’t necessarily need to find £200,000 upfront. What matters is understanding which interventions should happen first. Windows replaced today could be positioned and detailed to accommodate external insulation several years later. A roof upgrade could be carried out that futureproofs a future solar PV installation, while heating improvements might follow work to reduce the building fabric’s energy demand. A building passport would provide continuity across projects involving different contractors, budgets and, potentially, owners. Rather than starting from scratch with each intervention, everyone then has a record of the building’s intended direction.

Delegates suggested that routine renovations, such as kitchens, bathrooms, roofs and windows, could also trigger the creation of such building passports. The aim would be to avoid missed opportunities and costly work that may subsequently need undoing.

FIND REPEATABLE SOLUTIONS

The discussion also exposed a central challenge for retrofit on a mass scale. Existing buildings all require individual assessment, but treating every property as an entirely bespoke project makes improving millions of homes quickly difficult and expensive. Building archetypes could help bridge that gap.

One delegate described working on an estate containing around 2,500 homes, but only a handful of fundamental property types. Understanding those archetypes made it easier to predict costs, communicate with residents and develop repeatable solutions. This principle could also extend to standardised “kits of parts” for common building archetypes. Individual surveys would remain necessary because condition, alterations and previous work vary from building to building, but it would save designers from needing to reinvent every detail and junction.

For architects and specifiers, this offers a balance between standardisation and individual building requirements. Proven details and established combinations can provide a starting point while allowing flexibility where necessary.

WHO TAKES RESPONSIBILITY?

A whole-building approach like this raises an obvious question: who takes responsibility for coordinating the different specialists? Architects, consultants and retrofit coordinators were all discussed, although delegates agreed that the role mattered more than the job title itself. Without overall oversight, individual specialists can demonstrate that their own elements comply but nobody takes responsibility for how those elements perform together.

Architects can influence these projects before decisions become fixed. They can establish what the client wants the building to become rather than beginning with individual products. This means considering more than just energy performance. One delegate questioned whether a retrofit could be considered successful if the technical performance improved, but the building no longer met its occupants’ needs. To prevent this, adaptability, longevity, embodied carbon and future usefulness must form part of the initial discussions. It was a reminder that achieving a particular figure on an energy calculation should not become the sole objective.

WHAT DOES SUCCESS LOOK LIKE?

Another major question concerned how the industry determines whether completed retrofit work has achieved its intended outcomes. Installing a new system on its own doesn’t prove that the desired energy efficiency improvement has been delivered without some form of ongoing monitoring.

One delegate described visiting relatively modern homes that have strong predicted performance levels thanks to their use of triple glazing and mechanical ventilation with heat recovery, only to discover residents had switched off the ventilation because it was too noisy. While energy consumption must be considered, indoor air quality, comfort, overheating and the way residents interact with the building are all equally relevant.

Airtightness testing, thermography, commissioning and post-occupancy monitoring can establish whether buildings perform as intended. Yet measurement also raises questions about whose responsibility it is when those results fall short. Poor heating performance might stem from the equipment, system design, installation, controls, building fabric or occupant behaviour. Understanding the cause requires effective communication and clearer accountability across the team.

TACKLING OVERHEATING

Climate change brought another dimension to the discussion. While UK energy-efficiency measures have traditionally concentrated on reducing winter heat loss, delegates argued that summer performance deserves equal attention, especially as temperatures rise.

“If we are going to get these [high] temperatures [more regularly] and we don’t deal with the actual fabric, the heat loss may be addressed, but no-one is looking at the heat gain,” one participant said.

Responding to hotter summers simply by installing air conditioning also risks increasing energy consumption without addressing the underlying building performance. Instead the building fabric, glazing, ventilation, shading and the surrounding environment all influence whether buildings will remain comfortable throughout the year. Regardless of the specific technologies being discussed around the table, the focus repeatedly returned to the need to understand the way they interact with each other. Green roofs and PV arrays, for example, may complement one another, but structural capacity, maintenance, fire safety, insurance and the existing roof design must all be addressed before a system can be installed.

There may never be a universal specification for successful retrofit, but what can become more consistent is the process used to identify the right solution. First, assess the building, establish the desired outcomes and develop a long-term plan. Then understand how the building fabric and services interact, sequence improvements carefully and verify the completed building’s performance. For mass retrofit programmes, archetypes and repeatable details could make delivery faster and more affordable.

Specifiers have an opportunity to coordinate this, maintaining an overall view while specialists concentrate on their respective disciplines. But the ultimate measure of success has to be the performance of the building that is left behind.