Why do we Reuse Old Buildings Instead of Demolishing Them?

The Case For Adaptive Reuse

Progress in architecture is often measured by what we build next. Aging structures/projects are frequently seen as obstacles to development rather than opportunities. That approach no longer makes as much sense as it once did. Demolition is no longer the obvious answer. More projects are starting with the question of how an existing building can be adapted instead.

Known as adaptive reuse, the practice of transforming existing buildings for new purposes has become one of the defining movements in contemporary architecture. Instead of demolishing and rebuilding, these projects preserve a structure's embodied carbon while adapting it to meet today's needs, whether that's converting a factory into housing, a power station into a cultural venue, or an office tower into apartments.

There's a good environmental reason for the change. Buildings account for nearly 40% of global energy-related carbon emissions, while construction and demolition generate an enormous share of the world's waste. Every building that is reused instead of demolished avoids not only thousands of tonnes of material heading to landfill but also the carbon emissions associated with manufacturing new concrete, steel, and other building materials. In many cases, it can take decades for a newly constructed "green" building to offset the emissions created during its construction.

Adaptive reuse doesn't begin with a finished design. It begins with recognizing the potential in a building that most people have already written off. To see how this plays out in practice, here are some of the most interesting proposals and completed projects I have seen recently.

Hearn Generating Station, Toronto

For more than 40 years, the Richard L. Hearn Generating Station has sat largely empty on Toronto's waterfront. Completed in the 1950s, the coal-fired power plant once supplied electricity to much of the city before being decommissioned in 1983 as Ontario shifted away from coal generation. Since then, the massive industrial structure has been used only occasionally for film productions, exhibitions, and events, despite occupying one of the largest redevelopment sites in the Port Lands.

Today, the site is the subject of a proposed 30-acre mixed-use redevelopment led by PARTISANS, SvN, and ERA Architects. Rather than demolish the landmark, the proposal would preserve the existing generating station as the centerpiece of a new neighbourhood containing roughly 8,400 homes, commercial space, parks, and public amenities. The cavernous turbine hall would become a major cultural venue, while new residential towers would be built around and above portions of the existing structure.

The project, however, remains years away from construction. Beyond the engineering challenge of reusing a building this large, the surrounding Port Lands are still undergoing major infrastructure upgrades, including flood protection, new roads, utilities, and future transit. The scale of the proposal also means it would likely be built over decades rather than years. Whether the current proposal moves forward or not, the Hearn has become one of Canada's most compelling examples of the potential locked inside aging industrial buildings.

Chet Holifield Federal Building (The Ziggurat), California

Few buildings are as peculiar as the Chet Holifield Federal Building, better known as The Ziggurat. Designed by architect William L. Pereira and completed in 1971, the stepped pyramid was inspired by ancient Mesopotamian temples and quickly became one of Southern California's most recognizable landmarks. When it opened, the surrounding area was largely undeveloped. Over the following five decades, Orange County grew around it, changing the building from an isolated federal office into a defining feature of Laguna Niguel's identity. Despite its iconic status, the one-million-square-foot complex became increasingly underused as federal agencies downsized, eventually sitting largely vacant after its final tenants departed.

That chapter came to an end this summer when the U.S. General Services Administration sold the 89-acre property to Hoag Memorial Hospital Presbyterian for $207 million, making it one of the largest government property sales in U.S. history. While Hoag has committed to a long-term redevelopment strategy, it has yet to reveal exactly what the site will become. Given the scale of the property and its location in one of Southern California's most valuable real estate markets, the campus could realistically evolve into a major healthcare district anchored by hospitals, medical research, education, housing for healthcare workers, and complementary commercial uses. Whatever ultimately replaces or incorporates the Ziggurat, the site's sale reflects a broader trend: governments are increasingly shedding aging real estate portfolios, creating opportunities to rethink buildings that were never designed for today's cities.

Château Saint-Ambroise, Montreal

Not every adaptive reuse project needs housing to be successful. Montreal's Château Saint-Ambroise is a reminder that some of the best workplaces were never designed as offices in the first place. Originally built in 1882 as the Merchant Mills factory complex, the site later became home to Dominion Textile and toy manufacturer Coleco, employing thousands of Montrealers before industrial production gradually disappeared. By the late 1980s, the complex was largely abandoned. A decade later, rather than clearing the site, the buildings were converted into commercial lofts. Today, more than 200 companies occupy the complex, the majority working in film, advertising, architecture, design, photography, and other creative industries.

Much of that appeal comes from the buildings themselves. Long before electric lighting became standard, factoris relied on enormous windows to illuminate production floors. High ceilings, thick masonry walls, exposed timber, and generous floor plates were practical industrial decisions that happen to suit creative work remarkably well. The spaces feel open, receive exceptional natural light, and offer a level of acoustic and thermal performance that many contemporary office buildings struggle to replicate. It's no coincidence that former factories like Château Saint-Ambroise have become magnets for architects, designers, artists, and production companies.