These old Roman buildings could unlock how to build in a warming world

ROME — For centuries, historians and architecture critics have been embarrassed by buildings like San Giorgio in Velabro. The exterior of the medieval church is inoffensive enough: trim portico, unprepossessing facade, simple bell tower.

But step inside and the structure is a hodgepodge, seeming to break the rules of architecture right and left.

The nave is framed by rows of mismatched columns — some smooth, others fluted; some made of granite, others of marble.

They are topped with a motley mix of both Corinthian and Ionic capitals.

San Giorgio in Velabro, Interior's base pillar. Rome, Italy

Some columns needed extra material to accommodate their varying heights. They look like they came from a secondhand store.

Which is, in fact, roughly the case. San Giorgio is a “spolia” church, in which many of the basic architectural elements were reused from older buildings. Spolia is Latin for spoils, familiar in English usage from the phrase “spoils of war.” In architecture, it refers to the reuse of decorative and structural elements. The mismatched columns and other oddities throughout the nave of San Giorgio are signs of recycling.

Spolia architecture, including the curious churches of Rome, was long dismissed by historians and critics for seeming to lack the coherence and cohesion of proper classical architecture. While Renaissance architects reused ancient materials and sometimes entire buildings — including part of the colossal Baths of Diocletian, which Michelangelo redesigned as a Christian basilica — they often worked to make reused material look new, pristine and orderly. And for tourists today, steeped in the importance of historical preservation, the medieval plundering of ancient materials may feel like architectural sacrilege.

The heterogeneous aesthetic of the spolia churches was often attributed to the economic distress of the times. Although architectural recycling was common practice throughout antiquity, many of the spolia churches date from centuries after the heyday of Ancient Rome, when the city’s population was plummeting.

The floor behind the altar is decorated with Cosmatesque-style round slabs of inlaid stone from the 12th century, which were probably cut from even older recycled columns.

In the apse, the semicircular space behind the altar, the thin columns attached to the wall are capped with 6th-century capitals.

A small cross cut into the marble stairs leading to the raised chancel may be a sign that the stone was repurposed from an earlier, perhaps pagan, building and “christened” for its new home in a church.

But now, as the planet faces a climate crisis that could dwarf the human impact of the collapse of Ancient Rome, these churches are getting another look: as a model of the sort of recycling that is key to a sustainable global economy and building sector, currently responsible for more than a third of all greenhouse gas emissions.

Some historians have argued that the visual diversity of churches like San Giorgio wasn’t just a pragmatic response to the lack of new building materials but an intentional part of the design. The churches manifested a new compelling aesthetic. Which is why they are particularly inspiring today, when architects aren’t just experimenting with radical new ways to do something old — recycle buildings — but seeking to make recycled structures just as delightful as newly built, high-design ones.

Demolition, today, is a perverse luxury of economies where materials are cheap and labor expensive. It is a ubiquitous part of the architectural cycle — building, erasing and rebuilding — with no thought to the reuse of old materials, or the environmental cost of creating ever new supplies of concrete, steel and gypsum board. It is even a kind of spectator sport, with people gathering to watch and cheer the dusty annihilation of high-rises, bridges and old stadiums.

But it is a modern aberration. The reuse of old materials has been part of the basic economy of making buildings since the dawn of human habitation.

“The Romans were very good at recycling,” said Nick Jeffries of the Ellen MacArthur Foundation, a British nonprofit devoted to furthering the “circular economy” — so that basic goods and materials are reused, repaired, passed on, upcycled and recycled, rather than consumed, tossed aside or sent to the landfill.

Jeffries cited the example of the Theatre of Marcellus in Rome, about a 10-minute walk from San Giorgio. Finished about 13 B.C., it served as an open-air venue for four centuries, before some of its stone was repurposed for other structures, and the remains of its external walls provided shelter for infill residential structures. It later became a fortress and today it still houses a Renaissance-era palazzo, now subdivided, on its top level.

The Theater of Marcellus, finished about 13 B.C., was plundered for architectural material after it fell out of use in the A.D. 4th century. A 16th-century engraving imagines how it looked during its earlier years.

A substantial part of the structure remains today, with a Renaissance-era villa, now subdivided, built into its upper levels.

Construction in Rome, from ancient buildings to restoration projects today, has often involved the reuse and recycling of materials, said Renata Cristina Mazzantini, an art and architecture historian and director of Rome’s National Gallery of Modern and Contemporary Art.

She listed some of the variations: the wholesale repurposing of old structures such as the Theatre of Marcellus; the appropriation of building materials, say the stone of an old defensive wall, for new purposes, including residences; the reincorporation of decorative elements from one structure to another, sometimes as an aggressive form of ideological appropriation; and sophisticated forms of recycling, including the Cosmatesque style of decoration from later in the Middle Ages, when old Roman columns were sliced into thin paving pieces to create elaborately decorated floor designs and wall panels.

“The first thing they reused was metal, because that could be remade into other things, like weapons,” she said. But even at the most granular level, Rome recycled: Old limestone blocks could be burned to make the lime powder for mortar. And ancient architects, including Vitruvius, who left the most extensive record of how Rome was built, called for “rubble” when laying floors or foundations.

That breadth of reuse, from the most refined and valuable materials down to the level of crushed stone and gravel, contrasts sharply with much of contemporary construction.

In the United States, some 40 percent of the solid waste in landfills comes from the building sector, while less than 30 percent of building materials are recycled, according to an article Jeffries published in 2021.

“Designers today design for building performance,” he said in a Skype interview. They are primarily focused on making buildings that perform efficiently when it comes to energy use. But as buildings become more efficient, the larger climate impact comes from the carbon costs of their initial construction. The production of steel is responsible for 7 to 9 percent of global carbon emissions. The cement industry produces about 8 percent.

But there is growing appreciation for what can be reclaimed from older structures, and the concept of “deconstruction” is gaining ground in building design. The idea is that buildings should be designed to be unbuilt after their useful life is over, with the materials reused in new structures.

For now, deconstruction is more of a goal or design principle that an actual school of architecture. There is no definitive “look” to deconstruction. When materials are reused, they are often hidden from view, behind walls or gypsum board. And projects designed from the beginning to be disassembled are rare. But there are some intriguing early forays.

The stadium designed by Fenwick Iribarren Architects for the 2022 FIFA World Cup in Qatar used 974 recycled shipping containers fitted into a structural steel frame. It looks a bit like a circular parking garage or storage facility, with a wild assembly of colored containers — each fitted out to serve a different purpose, including food concessions, toilet facilities and prayer rooms — arrayed on different levels.

Mark Fenwick, president and founding partner of the firm, said much of the modular construction work was done in factories far from Qatar, so it didn’t involve as much danger for workers as other stadiums and infrastructure that were constructed in extreme heat.

“We could reuse every single piece of this building,” Fenwick said. Options for future use include repurposing it as two separate stadiums; reassembling it in another location; repurposing its elements for other uses such as housing; or, given its popularity, leaving it intact.

Stadium 974, designed by Fenwick Iribarren Architects for the 2022 FIFA World Cup in Qatar, was created to be dismantled and reused. Made from shipping containers fitted into a steel frame, its aesthetic is modern and purposefully motley, with the containers color-coded to indicate areas such as restrooms, concessions and prayer rooms.

While there are examples of structures being deconstructed and pieced back together in the same way for the same purpose, the larger goal is to design buildings in such a way that their basic materials can be returned to the circular economy. That is still a ways off.

“Designing for deconstruction isn’t the challenge,” said Dan Bergsagel, who heads sustainability efforts at the German engineering firm Schlaich Bergermann Partner. Rather, he said, it’s developing a culture of reuse, including adjusting building codes and regulations to allow recycled materials back into the market.

Advanced modeling systems, he said, could help ensure the suitability of reuse, cataloguing the stresses, loads and other forces each element endured during a building’s lifetime.

But right now, it is easier, faster and cheaper to demolish buildings and rebuild with all new elements.

Felix Heisel, director of the Circular Construction Lab within Cornell University’s architecture department, is an evangelizer for reuse. “If you look at the timber in a 100-year-old building, it is bone dry,” he said. “It has tighter grain, and the structural quality is phenomenal. If you compare that with what we get today, virgin timber is often twisting and turning the moment you start using it.”

In the United States, there are niche markets for salvaged materials — shops, websites and social media groups that sell elements of older buildings to architects, builders and the do-it-yourself community.

The challenge, Heisel said, is to scale all of this up to an industry-wide practice.

To the extent that demolition with reuse in mind is happening, it is providing lessons about how the design and engineering of new buildings could help make their materials easier to salvage later on.

In 2023, KL&A, an engineering and construction services company, helped “deconstruct” a 250,000-square-foot empty hospital building in Boulder, Colorado. The approach was guided in part by a 2020 city ordinance mandating that both commercial and residential buildings be deconstructed rather than demolished, with 75 percent of the materials from the disused structures diverted from landfill. In the case of the hospital, steel beams were carefully removed, tagged and slated for reuse in a variety of new projects, including a new fire station. Concrete was crushed and used as infill for the redevelopment of the property.

Steel beams removed from a hospital in Boulder were repurposed in a local fire station.

“They actually achieved 94 percent landfill diversion,” said Alexis Feitel, a director for KL&A.

Among the key takeaways for deconstruction-oriented design: Screws or bolts are preferable to more permanent joining methods. Avoid materials like spray foam insulation that are difficult to remove once applied to the structure. Buildings with complicated geometry, and lots of bespoke elements, can be hard to deconstruct and reuse. Modularity is an advantage.

But will applying those lessons make architecture ugly? Predictable, uniform and monotonous? Feitel acknowledged the concern. “We don’t want all of our buildings to look the same generic boxes, but we have to find a better balance between long-term values and aesthetics,” she said.

Modular architecture has been associated with the likes of the mail-order “kit houses” sold in the first half of the 20th century by Sears Roebuck and Co. It has also resulted in some fascinating structures, such as Tokyo’s Nakagin Capsule Tower, which fitted standardized “pods” designed to be mass produced into a structural framework. But that kind of building is often more popular with critics than with the public. The Nakagin tower, built in 1972, was demolished in 2022.

That’s where spolia churches of Rome become interesting. Maria Fabricius Hansen, an art historian at the University of Copenhagen who has written a book on the churches, argues that the reuse of old materials expressed a new Christian worldview. Just as the New Testament built on and rethought the Old Testament, the new churches reused past elements for a new purpose. The heterogeneity, which was often more pronounced the farther one stood from the altar, may have expressed human imperfection aiming at a higher sense of order. In other cases, incorporating pagan elements may have indicated a transcendence of the past.

“It is combination of the pragmatic reuse of the past and ideological pleasure in heterogeneity,” she said.

“When I teach on spolia,” she said, “and I want to convince people that the medieval Romans appreciated this variation, I compare it to when young people use secondhand clothes, or prefer clothes with holes on the knees, instead of Louis Vuitton, something very expensive or predictable.” It is, she said, rather like the idea of “shabby chic”: “I see spolia architecture as a kind of role model that inspires reuse and integrates the past in contemporary architecture.”

The path to sustainable architecture is fairly clear, and it requires not just structures that are more efficient, but building less, reusing more and recycling everything else. To get there, however, isn’t just a technical or engineering question.

We must find that new world beautiful — whether in modular architecture that is spare, minimalist and reusable; or in a new architecture that embraces the persistence of the past, an aesthetic of assemblage and mix-and-match material bravura.

One place to start is on a quiet street not far from the Tiber River, where the church of San Giorgio in Velabro has for centuries been telling the world that past is present, and there is no shame in that.

Ahmed reported from Washington.