Retrofitting Europe’s ageing buildings

Carlos Ochoa, senior researcher at the Tyndall National Institute, outlines how the EU-funded DigiFab project aims to accelerate energy retrofitting across Europe through digitalisation, prefabrication, and occupant-centred design.

With 85 per cent of Europe’s building stock having been built before the year 2000, buildings account for a substantial share of energy demand. “We are using 42 per cent of our energy to heat up these buildings,” Ochoa explains. While deep renovation is essential, progress remains slow. “We are only doing 1 per cent as an average in Europe per year.”

Traditional approaches to energy renovation face multiple barriers. “Traditional energy retrofitting is very disruptive,” Ochoa explains. “It takes a lot of time, and it is also very expensive.”

Prefabrication is often proposed as a solution, but uptake has been limited. “We have so many buildings, and prefabrication is, by definition, something that repeats itself,” he says, highlighting the difficulty of applying standardised solutions to highly varied structures.

A lack of reliable information is another obstacle. “If you take a building from the 1950s, you are lucky if you have the plans, and therefore you have to start guessing what you have inside and then try to adapt to that kind of building.”

Information is also fragmented across stakeholders. “The building managers know something, the inhabitants know another thing, the constructor knows something else, so there is nothing centralised.”

Logistics further complicate matters. “You need a very well-detailed logistic plan in order to tackle prefabrication,” Ochoa says, warning that, without this, “this can make it unprofitable, especially for construction SMEs”. Occupant acceptance is equally critical as “when we are dealing with occupants, we have to take into account their desires, their motivation, in order to provide acceptance and cooperation”.

DigiFab

The DigiFab project, funded in the context of Horizon Europe by the European Commission, seeks to address these challenges through a fully digitalised renovation process. “The project proposes energy retrofits across the EU for several building typologies,” Ochoa says, with the aim of “strengthening the value chains”.

Central to this is a shared digital backbone. DigiFab proposes “a digital process as a single source of information”, replacing fragmented data flows where “you go one way and look for documents in another”.

Accurate data collection is essential. “We are proposing using laser scanning and surveying in order to make a digital twin or BIM model of the building,” Ochoa explains, capturing both interior and exterior features. “This is to have accuracy when developing retrofitting components and minimise thermal bridging.”

The process also includes “a manual inventory of the wall conditions” to assess load-bearing capacity, resulting in “a BIM model for the energy analysis”. This information is then translated into simulation tools. “We define the baseline and the target that we must achieve,” he says, and “recommend how we can reach, for example, the BER B2, according to characteristics like the thickness and the type of technology suitable for the site”.

All data is shared through a cloud-based platform. “This is information that will be available in a proposed data cloud so that the manufacturers can use it,” Ochoa explains.

Social acceptance

A distinctive feature of DigiFab is its focus on social acceptance. “We are getting the occupant and stakeholder input through a co-creation process in which the innovations of the future are co-designed with the users themselves,” Ochoa says.

These sessions are carefully structured. “If you ask people all of a sudden what they want, they might go in a different type of conversation, so these are sessions that are guided in order to get the relevant inputs.

“The drivers are not only carbon emissions. In the Austrian demonstrator, for example, people are cooperating because they are going to get an elevator. “Energy renovation becomes acceptable because it makes their life easier.”

User preferences also shape technical decisions. “In the traditional energy analysis, specialists may say eliminate thermal bridges, take off the balconies, but people like them and we need to account for this.”

Industrialised technologies

DigiFab integrates a range of prefabricated solutions. “We are developing lightweight concrete panels that have insulated and recycled materials,” Ochoa says, alongside, bio-based material panels, made from wood waste products.

On active façade systems, he says: “We have active heating and cooling façade elements,” he explains, which circulate hot water through the façade. In addition, “we have PV panels that are just plug and play”, combined with energy management solutions to make buildings smarter.

These systems are customised through digital design. “This is how to customise an industrial product,” Ochoa says, while “the carbon footprint is reduced compared to conventional systems”.

“Lifecycle impacts are also considered, with the rollout of lifecycle analysis calculations considering the extended lifetime of the building,” he explains. “Now we are extending it maybe another 20 or 30 years. Construction waste is minimised, and any that is generated is sent to appropriate locations for recycling.”

Speed and safety

Installation is designed to be rapid and low impact. “We are going to have 200 square metres of surface in two days,” Ochoa says, using large, prefabricated elements. The approach aims for 30 per cent reduction in costs by eliminating delays and intermediaries.

Worker safety is integrated through digital monitoring of the construction site. “The workers are wearing sensors on their clothes and helmets,” he explains, allowing detection of falls, proximity to machinery, and excessive noise exposure.

Early results are promising with a study on the EU legal framework, also including Ireland, Ochoa says, concluding that it is “mostly positive” for prefabrication.