The Greenest Building on the Block

November 5, 2021 | by Starr Herr-Cardillo

Rehabbing a rowhouse in the Mantua section of West Philadelphia. | Photo: Peter Woodall

Editor’s Note: A version of this story was published in the Fall 2021 issue of Extant, a publication of the Preservation Alliance for Greater Philadelphia.

“Never demolish, never remove or replace, always add, transform, and reuse!” That’s the motto of Lacaton and Vassal, the French architecture duo awarded architecture’s prestigious Pritzker Prize earlier this year. Those in the architecture world remarked how refreshing it was to see a firm with such a humble and socially responsible ethos bestowed the field’s highest  honor. The architects’ approach stresses minimal intervention in–and respect for–what already exists in the built environment. 

While the duo is particularly known for designing elegant, economical upgrades to existing public housing complexes, minimizing displacement of residents while introducing flexible communal spaces and light-filled atriums that enhance quality of life, their inherently humane focus makes their projects environmentally sustainable as well. 

“Demolishing is a decision of easiness and short term,” Anne Lacaton told The Guardian. “It is a waste of many things–a waste of energy, a waste of material, and a waste of history.” Lacatan and Vassal don’t describe themselves as preservationists–at least not in the narrowest of terms. But their inspired and refreshing work refutes many developers’ persistent claims that reuse simply isn’t feasible, that the numbers can’t pencil out, and that creative solutions aren’t worth the effort. The architects’ approach, in fact, exemplifies the environmental, social, and economic sustainability that preservation and adaptive reuse have to offer.  

Relevant Insights

Preservationists have been trying to draw attention to the environmental benefits of building and materials reuse for decades. Perversely, the building industry’s standards related to sustainability have virtually ignored any overarching philosophy of pragmatic reuse. Even the concept of materials recycling, which a public already accustomed to recycling can easily understand, has never been integral to the messaging around buildings and sustainability. 

This may stem partly from a narrow perception of preservation as a profession focused on the precise restoration of buildings of superior historical significance. Green building advocates may not realize that preservationists are open to flexible adaptive reuse and have relevant insights to contribute to solutions for our pressing environmental problems. 

It’s telling that the vast majority of the building industry’s efforts regarding sustainability disproportionately emphasize the benefits of new “green” products like vinyl windows, technical innovations like solar panels and low-flow toilets, or new, “sustainably” manufactured materials like bamboo flooring. The reality is that green building is big business. According to the current Market Research Future report, the global green building materials market is expected to climb from $238 billion to $425.4 billion by 2027.

19th and early 20th century rowhouses in University City, like this one on 44th Street near Chestnut, are being torn down and replaced by multi-family buildings marketed toward students. | Photo: Peter Woodall

The green building industry is heavily driven by LEED, which stands for Leadership in Energy and Environmental Design and is the world’s most widely used green building rating system. LEED awards points for green upgrades made during construction or renovation, such as water efficiency or the use of more sustainable materials. Projects that score enough points to meet specified thresholds are awarded different certifications: certified, silver, gold, and platinum. When the U.S. Green Building Council first developed and launched the ratings system in 1998, it didn’t award any points for reuse of an existing building. 

Although that oversight has since been amended, professionals working at the intersection of preservation and sustainability are quick to point out LEED’s shortcomings. Retrofits of existing buildings–that is, essentially reusing an entire building envelope– often aren’t awarded as many points as new  “green” construction. Coordinating projects that rack up enough points to meet LEED qualifications while still retaining historical fabric–like original windows–can require difficult maneuvering. In most cases, the system fundamentally rewards replacement over reuse. In an online discussion on a forum for historic preservation professionals, George Kramer, a preservationist and environmentalist based in Ashland, Oregon joked, “[The LEED system] gives building owners an extra push to build anew, ignoring the fact that tearing down an existing building and replacing it with ‘sustainably harvested wood’ is about the dumbest, least efficient use of resources imaginable.” 

It all comes down to embodied energy, says Bob Yapp, president of Preservation Resources Inc., who has been rehabbing buildings for decades. Generally speaking, embodied energy is the amount of energy expended to mine, mill, refine, or fabricate, and transport materials (the more current term “embodied carbon” refers specifically to the carbon emitted in these processes, acknowledging that some energy comes from renewable sources). While there are different and specific ways to calculate and define the energy used to build (and operate) buildings, the gist of the embodied energy argument when it comes to preservation is: the embodied energy of materials that already exist in older buildings–and the energy expended to construct them–is a sunk cost, all of which is lost if those buildings are torn down and the materials tossed in the landfill. Yapp and others are frustrated that LEED doesn’t adequately recognize those inherent benefits. “I make old buildings energy efficient all day long,” Yapp said, “I should get a platinum LEED for just saving the building from going to the dump.”  

Language Barriers

San Antonio’s Historic Preservation Office has been at the forefront of making the connection between preservation and sustainability by both integrating preservation into the City’s long-term sustainability plan and initiating policies and programs that encourage deconstruction and material reuse. One of the key people behind those efforts is Stephanie Philips, Senior Historic Preservation Specialist. Through her work on sustainability, Phillips has gained insight into how preservationists can better communicate with those outside of the field. 

Developing a grasp of universal language, she says, is key. “We were finding that people were engaging with preservation topics, but not using the language we normally use,” Phillips explained, “No one is calling [reuse] ‘preservation.” Instead, she says, they’re using terms like “existing buildings,” “embodied carbon,” and “circular economy,” which preservationists need to hear, absorb, and employ as well.  

Phillips also believes that practitioners need to get out of their siloes and be prepared to have conversations with people who aren’t preservationists, per se. Critical to San Antonio’s success, she says, has been the City’s willingness to create space that makes those conversations possible, bringing in groups that wouldn’t normally be in the same room–staffers from the City’s preservation and sustainability offices, for example–to interact and exchange ideas. None of those connections would have happened without a strong push from leadership at the Office of Historic Preservation. 

Haphazard demolitions in which few if any materials are recycled or reused such as this tear-down in Powelton are all too common in Philadelphia. | Photo: Peter Woodall

The City of Philadelphia did recently create a cross-departmental working group in response to a Historic Preservation Task Force recommendation, but the kind of cross-departmental communication exemplified by San Antonio is not happening yet. The City’s newly released Climate Action Playbook doesn’t address the wastefulness of demolition at all. According to the Playbook, buildings and industry account for 75 percent of greenhouse gas emissions in the city. That number mostly refers to “operational energy”–the energy used by a building’s occupants once it is constructed and is in use. The City rightfully stresses upgrading existing building stock so that it is more energy efficient. But that goal needs to go hand-in-hand with prioritizing retrofits and reuse whenever possible. To realize the enormous potential for sustainability in Philadelphia’s existing building stock, people who are thinking about embodied energy and demolition waste involved need to be involved in the planning process. 

Rowhouse Power

As a city of rowhouses, Philadelphia is primed to be a model of sustainability. Rowhouses make up more than 70 percent of housing units in Philadelphia and are inherently sustainable. “The rowhouse is so good, it’s so perfect,” says Jeremy Avellino, whose firm, Bright Common Architecture and Design, specializes in sustainable design and has extensive experience with both infill construction and rehabs. “The Philly row house could represent a revolution in lowering our carbon footprint simply because of what it already is.”

The type of low-rise density that rowhouses provide offers many sustainability benefits. Not only are they cost effective and affordable, they function as a cohesive unit and insulate one another. Most importantly, they’re relatively sturdy, made of durable materials–in Philadelphia, most commonly brick–that easily last hundreds of years. At the same time, the venerable, durable, efficient rowhouse is also well-suited to upgrading and energy retrofitting.

Passive House design is Avellino’s passion. Whether through new construction or substantial energy retrofitting to existing buildings, the Passive House model focuses on drastically reducing the amount of energy needed to heat and cool by keeping an airtight building envelope to minimize the loss of conditioned air. The key metric for achieving Passive House standards is thermal efficiency, already an inherent quality of rowhouses, says Avellino, thanks to those shared walls that help neighboring houses preserve heat. 

Still, lowering energy expenditure and increasing energy efficiency in Philadelphia’s existing housing stock to Passive House levels presents challenges. To assist homeowners looking to bring their row houses up to Passive House standards, Avellino and other volunteers recently released The Passive Rowhouse Manual. For those with the means to do so, making such upgrades is a moral imperative, Avellino believes. 

But there are massive challenges. Avellino realizes that individual actions alone won’t have an impact on the impending environmental crisis without larger scale, coordinated efforts. Because broader messaging around sustainability tends to fixate on individual actions aimed at consumers with disposable income, even the best-intentioned climate activists sometimes fail to acknowledge how environmental sustainability intersects with race and class. Housing, for example, is both a huge environmental and racial equity issue. Disinvestment driven by racist housing policies, white flight, and poverty has left people with very limited resources, and, as a result, thousands of Philadelphia’s rowhouses are in precarious condition. Avellino feels strongly that any meaningful effort to preserve and retrofit the city’s extensive housing stock must be accessible to all, particularly to homeowners who can’t afford to make the necessary upgrades on their own. A city-led initiative that would fund of upgrades and stabilization of existing rowhouses and other housing stock, Avellino says, would be a huge step toward climate resiliency.

Restore, Repair, Renew

Bright Common Architecture + Design rehabbed this Fishtown rowhouse to meet the Passive House Standard. | Photo: Peter Woodall

The Healthy Rowhouse Project (HRP) was one such initiative that sought to address the intersectional nature of housing and sustainability by highlighting the connection between home maintenance and repair and public health. Although its creators didn’t bill HRP as a “sustainability” initiative per se, it absolutely was. The concept took a new form as Restore Repair Renew, a Philadelphia Housing Development Corporation (PHDC) preservation loan program headed by former HRP Director, Jill Roberts. By providing low interest loans to residents who might otherwise struggle to secure them, Restore, Repair, Renew helps homeowners make critical repairs that help keep their homes functional and safe. It’s exactly the type of preservation program Avellino is advocating as essential at a much larger scale. 

Statistics compiled by the Healthy Row House Project highlight the fact that many lower-income homeowners in Philadelphia own their homes outright. But when maintenance costs and needs grow so large that they lead to major structural issues like holes in the roof or serious structural cracks, people who can’t afford the repairs are sometimes forced to walk away from their homes. 

Roberts points out that all of these issues can be traced back to racism that’s embedded into systems around property and homeownership. “We as a country have institutionalized poverty and that’s because people were shut out of the capacity to own homes and gain meaningful wealth because of the color of their skin,” Roberts told me. “We are nibbling at the edges with the work we are doing until this country gets right with race and figures out a way to deal with reparations.” Roberts believes that those reparations could take the form of providing money to people to repair and update their homes that they wouldn’t have to pay back. This, she says, would be one way to help “catch people up and give them a level playing field.” Moreover, it would serve the goals of both preservation and sustainability.

Avellino wholeheartedly agrees: “What we need is to create a culture in which healthy, zero energy housing is accessible to all people who already possess the knowledge to make their own communities resilient. And we need earth-honoring, anti-racist policies to get us there ASAP.”

Keeping, Not Demolishing

Roberts and Avellino share a bold and exciting vision. Celebrating the inherent efficiency of Philadelphia’s most iconic building type, they see an opportunity to provide lower-income homeowners with subsidized, sustainable upgrades to their existing homes, bolstering communities by creating opportunities for job training programs focused on skilled building trades, and addressing climate change in the process. 

Another, simpler word for this nuanced and holistic view is “preservation.” Climate resiliency begins with recognizing the value–and yes, the energy–embodied in the abundant store of buildings we already have. “If we talk about keeping buildings instead of demolishing them,” said Lacaton and Vasal in a recent interview, “ it’s the first step towards sustainability; to make sustainable what already exists.” And who better to take on that challenge than preservationists?


About the Author

Starr Herr-Cardillo is a staff writer for Hidden City Daily. When she’s not covering local preservation issues or writing editorials for Hidden City, she works as a historic preservation professional in the nonprofit sector. Born and raised in Tucson, Arizona, Herr-Cardillo was drawn to the field by a deep affinity for adobe and vernacular architecture. She holds a Certificate in Heritage Conservation from the University of Arizona and an M.S. in Historic Preservation from PennDesign.


  1. Roseanne Hunt-Harkin says:

    So much waste goes into demolition and rebuilding. Row houses in Philadelphia are a dynamic group, building a Community.
    Roseanne Hunt

  2. Marianna Thomas says:

    Not only does the Green Building Council point system understate benefits of existing rowhouses, but also the Philadelphia’s new zoning code, adopted in 2013, provides an economic incentive to teardowns. the old 35-foot maximum height was increased to 38 feet, just enough to squeeze a 4-story house onto a lot(with the lowest floor partly below street level), realizing a 33% increase in rental floor area. In rapidly developing neighborhoods, the pre-2013 projects are easily recognizable by their 3-story height, which is often aligned with floor levels in existing blocks. The houses started under the new code are taller than their neighbors with floor levels, openings and thresholds that are not aligned with existing houses. The result is dissonance rather than harmony.

  3. In the era of climate change, more and more emphasis is being placed on a building’s “green” credentials, as environmental impact leads decisions around design, construction and operations.

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