Could composites be the future of high-performance building systems?

Architects, specifiers and building-system designers are under growing pressure to deliver longer lifespans, lower maintenance and better energy efficiency. Composite materials – valued for their thermal stability and long-term durability – are attracting renewed interest as a result. That interest is about to be reinforced by regulation: a dedicated Eurocode for fibre-polymer composite structures is now working its way through the European standards process, and it will give engineers the harmonised design guidance that steel, concrete and timber have had for decades.

Sustainability conversations in construction often gravitate toward embodied carbon and headline projects such as Mjøstårnet, the 18-storey timber tower in Norway currently recognised as the world’s tallest timber building. But operational durability over decades of exposure is a separate, increasingly recognised metric, and one where composites make their case most directly: in windows, doors and facade systems exposed to constant thermal cycling dimensional stability rather than embodied carbon is often the more immediate design constraint.

From technical specification to Eurocode

Composites have never had a Eurocode of their own. CEN/TS 19101, Design of fibre-polymer composite structures is changing that. Published in November 2022 by the CEN/TC250 Working Group 4 after more than 12 years of technical development, it is currently a European technical specification rather than a full Eurocode – a status that puts it through a two-to-three-year trial period in which engineers apply it on live projects before the European Committee for Standardisation (Comité Européen de Normalisation – CEN) decides whether to convert it into a formal standard. That decision is expected this year, and, if it goes ahead, composites will likely take the Eurocode 11 designation, since Eurocodes 0 through 9 are already assigned other materials and Eurocode 10 looks set to be assigned to structural glass.

According to the European Composites Industry Association (EuCIA), the aim is to put composites “on the same level as conventional construction materials” by giving engineers a clear specification framework and the design confidence that comes with a recognised code. That matters commercially as much as technically: without a Eurocode, structural composites have had to be justified project-by-project through bespoke technical approvals, which adds cost and risk that steel or concrete specifications don’t carry. A settled code removes that friction and should make composites a default option for specifiers rather than an exception requiring special justification.

Why performance is the real driver

Behind the regulatory case is a performance case. Buildings are being asked to do more: larger glazed areas, slimmer framing, tighter envelopes and much longer service lives, all while meeting stricter airtightness and energy targets. Windows and doors – responsible for around 40 percent of a typical building’s heat loss – are where these pressures are sharpest. Repeated thermal movement in framing materials gradually degrades seals and airtightness, which is why dimensional stability under temperature change, not just at installation but across decades of use, has become a specification priority in its own right.

None of this is theoretical. Fibre-reinforced polymer bridges are already in service across the Netherlands and elsewhere in Europe, valued for being lighter, more corrosion-resistant and considerably faster to install than steel or concrete equivalents, particularly on sites where load-bearing capacity, access or construction time are constrained. What has been missing is not evidence that composites work structurally, but a harmonised, nationally recognised code that lets engineers specify them with the same confidence, and the same insurability, as conventional materials.

This is where composites have a genuine material advantage. Their coefficient of thermal expansion is typically around three times lower than aluminium’s, which can mean less movement, fewer compromised seals and less corrective maintenance over the building’s life. Reduced component weight also simplifies installation and handling. Combined, these properties support the minimalist, tight-tolerance glazing and facade systems that architects increasingly want to specify.

Lifecycle value over upfront cost

Upfront material cost still matters, but it is no longer the only test a material has to pass. RICS has pushed carbon and asset management assessment further into mainstream practice, and initiatives such as the RIBA 2030 Climate Challenge and Passivhaus principles are reinforcing the same shift toward operational performance over a building’s full-service life.

Judged on that basis, materials that hold their dimensional and sealing performance for decades reduce the replacement, repair and energy waste that shorter-lived alternatives generate – a lifecycle argument that composites, with their low thermal movement and corrosion resistance, are well placed to make.

That case isn’t without complication. Most high-performance composites are thermoset polymers, and their cross-linked molecular structure makes them genuinely difficult to recycle at end of life, unlike steel or aluminium. Research into dynamic covalent networks, such as vitrimer resins, is starting to offer routes to reprocessing, but mechanical recyclability remains behind that of conventional structural materials. Any credible lifecycle argument for composites has to weigh their operational durability against this unresolved question, rather than treating circularity as settled.

Conventional materials will remain central to construction, and no single material solves every challenge. But as performance requirements tighten, a material’s ability to hold its dimensional and sealing performance over decades will matter more than it has historically – and for the first time, composites will have a Eurocode to back that case up.