The Future of Architecture: Retrofitting Buildings

Written by: Louise Deltheil

Edited by: Iris Bisson

Some buildings have architectural or historical characteristics that make them significant for local historic preservation (Historic Building Definition - Architecture Dictionary, 2025). In the European Union (EU), each country has its own criteria to define a historical building, but often takes into account cultural significance, age of building, architectural value, heritage, and public interest (A Fresh Take on Heritage: Refurbishment of Historical Buildings | BUILD UP, 2024). There are many historical buildings in European countries - nearly 45,000 buildings in France as classified by the Ministry of Culture and 379,443 buildings in the UK according to the National Heritage List (Monuments Historiques En France - a Living Heritage - Destination Tourisme, 2024; Historic England, 2023). Building types range from very famous buildings, like the Eiffel Tower, to small elements in homes, such as 18^th century stone stairs.

In Canada, more than 13,000 buildings are listed on the Canadian Register of Historic Places (HistoricPlaces.ca - Home, n.d.). By comparison, almost 90,000 sites are listed on the U.S.’s National Register of Historic Places (National Register of Historic Places, 2019). These buildings range from inhabited houses and churches to commercial and even administrative buildings, parks, and other natural sites (Humphreys, 1980). In the U.S., the National Park Service is responsible for choosing which properties to recognize for their significance in American history and culture (National Register of Historic Places, 2019). Meanwhile, Canada’s Historic Places is a collaboration between each level of government, who collectively manage the protection of Canadian historical buildings (HistoricPlaces.ca - Home, n.d.).

Documenting historic places is crucial to protecting a country’s historical and cultural heritage. Even with the Canadian Register of Historical Buildings, “over 20% of Canada’s historic buildings have already been demolished” (HistoricPlaces.ca - Home, n.d.). In many cases, historical buildings are demolished to make space for newer and more modern buildings, since older buildings lack newer technologies, and have a greater ecological footprint. Yet, demolishing and rebuilding costs a lot of resources and energy as well; in 2022, the construction industry created 37% of CO2 emissions (Panakaduwa et al., 2024) (Final Energy Consumption of Buildings Relative to Other Sectors, 2022 – Charts – Data & Statistics, 2022).

Why should historical buildings be retrofitted?

Retrofitting buildings uses less energy and emits less CO2 than demolishing and reconstructing new ones. This is an important consideration for countries with environmental goals they need to hit. For example, according to the European Green Deal, the EU aims to be climate neutral by 2050 (European Commission, 2025). To achieve these types of goals, countries have to reduce their greenhouse gas emissions and non-renewable energy consumption in every industry, including construction.

Sustainably retrofitting buildings has significant benefits, making the process an important consideration when deciding whether or not to demolish. One of the biggest reasons historical buildings need to be retrofitted is to improve their energy efficiency (A Fresh Take on Heritage: Refurbishment of Historical Buildings | BUILD UP, 2024). In particular, inhabited historical buildings need the addition of new HVAC (Heating, ventilation, and air conditioning) and renewable energy systems to reduce the building’s energy cost in the long run (Iwuanyanwu et al., 2024). With better insulation and improved ventilation, sustainable retrofitting reduces the presence of harmful pollutants inside and noise pollution coming from outside. Better control of indoor environments improves residents’ health, encouraging people to move into retrofitted buildings rather than into more modern ones (Iwuanyanwu et al., 2024).

What are the issues with retrofitting?

Unfortunately, retrofitting historical buildings comes with a handful of problems that can have a great impact on the process and end product. Most of the problems stem from the age of the building, whether the issue be structural, financial, or political.

Building codes, used to ensure safety and regulate construction, make retrofitting complicated. Each country’s government has building codes and standards, which are updated very often. In the U.S., building codes are updated every three years, while in Canada, they update every five years (Bob, 2025; Beya, 2023). Additionally, codes can differ between states and provinces, and some cities even use different versions of them (Beya, 2023). Keeping track of all these regulations becomes difficult, especially because these codes are written for modern buildings. Older buildings were designed for older technologies, often making them incompatible with newer innovations. For example, the roofs of older buildings were designed to hold a lesser weight than buildings today; green roofs and newer HVAC systems would add too much weight to these historical buildings, making them structurally unsafe (Iwuanyanwu et al., 2024). To fix this issue, the structure of the older building needs to be updated or added on to in order to create a higher load threshold. Unfortunately, changing the structure of a building comes with two main problems: heritage and cost.

When retrofitting an older building, especially a historical one, the conservation of heritage is an important issue. Unfortunately, the building’s façade often has to be changed slightly, or significantly, depending on the structural needs of the renovation (Panakaduwa et al., 2024). This can change the building’s appearance fundamentally and impact the choice of retrofitting over demolition. Retrofitting historical buildings is a balance between incorporating innovation and conserving heritage.

Changing a building’s structure while adding innovative technology and preserving its heritage has a high cost. Although, in the end, retrofitting reduces the cost of living to compensate for the initial cost, it takes a long time to pay back. As for most construction projects, funding is extremely limited because it mainly comes from the owner or developer’s pocket. The delayed financial advantage makes a lot of potential investors squeamish at the idea of funding retrofitting projects (Iwuanyanwu et al., 2024). Lack of funding also makes acquiring permits hard. To obtain a permit, the owner has to hire a team of architects and engineers to plan enough of the project to convince the governmental power in their region. Oftentimes, a permit is not granted on the first attempt, meaning that the owner must pay a lot before official design and construction starts (Iwuanyanwu et al., 2024).

More likely than not, old buildings are already occupied no matter their function, meaning that retrofitting projects must also keep the building’s inhabitants in mind. On top of noise and pollution, the need for temporary relocation as well as disturbances to the daily lives of the residents are a concern. For instance, adding, replacing, or connecting new electrical or plumbing systems inevitably causes disruptions to inhabitants, which increases cost and complexity of retrofitting (Iwuanyanwu et al., 2024).

The listed issues of building codes, structural limitations, heritage, cost, and occupancy all add complexity to a retrofitting project; however, the advantages of improving energy efficiency through the installation of newer technologies make up for that obstacle. There are plenty of successful retrofitting projects throughout the world, such as the Willis Tower in Chicago, the BedZED in London, and even the Empire State Building in New York City (Iwuanyanwu et al., 2024).

Case Study: The Willis Tower (a.k.a. Sears Tower) in Chicago, Illinois, USA

In 2015, Gensler, an architectural services company, was hired to renovate the Willis Tower. Their goals were to connect the building to the surrounding streets, reduce its carbon footprint, make it more human-centric, and preserve its heritage. The project faced several issues, including managing underground structural constraints and preserving the building’s heritage when changing the material of its façade. However, keeping the tower open and functional for the 15,000 tenants during the Covid pandemic was the biggest challenge they faced. (Willis Tower Repositioning / Gensler, 2022)

To connect the building to the outside streets, Gensler changed the red granite base, which looked similar to a fortress, into a transparent podium, encouraging people to enter for leisure while maintaining the character of the building. Hints of terracotta were incorporated into the interior design to remind visitors of the rich history of the neighborhood. Additionally, a publicly accessible outdoor roof park, measuring 30,000 square feet, was installed to further connect the building to the neighborhood. It also helped mitigate the heat island effect by increasing the presence of nature in a dense city. (Willis Tower Repositioning / Gensler, 2022)

To help increase the building’s energy efficiency, Gensler replaced HVAC systems, added energy-efficient lighting, and implemented advanced building controls (Iwuanyanwu et al., 2024). The changes led to a 34% reduction in energy consumption and in carbon footprint, as well as reduced annual operating costs by millions of dollars (Iwuanyanwu et al., 2024). The building successfully achieved the status of LEED Platinum - the highest ranking in one of the most recognized indicators for sustainable buildings (Willis Tower Repositioning / Gensler, 2022; USGBC, 2025).

Conclusion

Although retrofitting historical buildings comes with many issues to navigate, such as building codes, structural limitations, heritage, finance, and occupancy, the advantages it brings in terms of sustainability outweigh the disadvantages. Energy efficiency improvements, along with an overall reduction in the building’s carbon footprint and long-term financial costs, prove that retrofitting buildings is a better solution than demolishing and rebuilding. Furthermore, retrofitting preserves the importance of historical buildings, allowing them to retain their charm and character while ensuring they are fit to be occupied in the modern day. Retrofitting, as a sustainable and cost-effective alternative to demolition, is the future of architecture all around the world.

References

A fresh take on heritage: refurbishment of historical buildings | BUILD UP. (2024, May 8). 

Europa.eu. https://build-up.ec.europa.eu/en/resources-and-tools/articles/fresh-take-heritage-refurbishment-historical-buildings.

Beya, C. (2023, March 17). Canada’s building codes and standards need to get with the times.

Canadian Architect. https://www.canadianarchitect.com/canadas-building-codes-and-standards-need-to-get-with-the-times/.

Bob. (2025, July 6). How Often Are Building Codes Updated? Understanding The Update 

Process And Its Importance - ConcreteCaptain.com. ConcreteCaptain.com. https://concretecaptain.com/how-often-are-building-codes-updated/.

European Commission. (2025). 2050 long-term strategy. Climate.ec.europa.eu; European 

Commission. https://climate.ec.europa.eu/eu-action/climate-strategies-targets/2050-long-term-strategy_en.

Final energy consumption of buildings relative to other sectors, 2022 – Charts – Data & 

Statistics. (2022). IEA. https://www.iea.org/data-and-statistics/charts/final-energy-consumption-of-buildings-relative-to-other-sectors-2022.

Historic Building Definition - Architecture Dictionary. (2025). Archdictionary.com. 

https://www.archdictionary.com/historicbuilding.

Historic England. (2023, November 29). Designated Assets Indicator Data | Heritage Counts | 

Historic England. Historicengland.org.uk. https://historicengland.org.uk/research/heritage-counts/indicator-data/assets/.

HistoricPlaces.ca - Home. (n.d.). HistoricPlaces.

https://www.historicplaces.ca/en/home-accueil.aspx.

Humphreys, Barbara A. and Meredith Sykes. The Buildings of Canada. (1980). Environment 

Canada Parks Service. buildingsofcanada.pdf.

Iwuanyanwu, Obinna, Ifechukwu Gil-Ozoudeh, Azubuike Chukwudi Okwandu, & Ike. (2024). 

Retrofitting existing buildings for sustainability: Challenges and innovations. Engineering Science & Technology Journal, 5(8), 2616–2631. https://doi.org/10.51594/estj.v5i8.1515

Monuments Historiques en France - a living heritage - Destination Tourisme. (2024, August 22). 

Cparici. https://cparici.com/en/historical-monuments-in-france/.

National Register of Historic Places. (2019). Gsa.gov. 

https://www.gsa.gov/real-estate/historic-preservation/historic-building-stewardship/national-register-of-historic-places.

Panakaduwa, C., Coates, P., & Munir, M. (2024). Identifying sustainable retrofit challenges of 

Historical Buildings: A systematic review. Energy and Buildings, 313, 114226–114226. https://doi.org/10.1016/j.enbuild.2024.114226.

USGBC. (2025). LEED rating system. USGBC. https://www.usgbc.org/leed

Willis Tower Repositioning / Gensler. (2022, September 24). ArchDaily. 

https://www.archdaily.com/989401/willis-tower-repositioning-gensler.