As urbanisation continues to accelerate, energy-efficient and low-carbon solutions for buildings are needed to make cities sustainable. To reach the climate goals of the Paris Agreement, all buildings should be net-zero carbon by 2050. What does this mean?
Buildings are responsible for almost 39% of carbon emissions globally, according to the International Energy Agency. While the actual manufacturing of buildings accounts for 11% of all emissions, building operations, which continue as long as the building is being used, make up 28% of all carbon emissions annually.
When fighting climate change, it is therefore vital to focus on how existing buildings can be modified to reduce those numbers.
Historic and iconic buildings serve as great examples of how diligently designed retrofits can bring older construction up to current standards. The Empire State Building in New York has been under extensive retrofits over the last decade and is now 100% powered by wind energy.
Anna Laura Pisello, currently an Assistant Professor of Applied Physics at the University of Perugia, Italy, was a graduate research assistant at Columbia University in New York when the Empire State Building was undergoing its first retrofits to gain energy efficiency 13 years ago.
“I studied and wrote about the LEED certification process of the Empire State Building. It was a very successful retrofit that also sent a powerful message. The work done on iconic buildings to become energy efficient can inspire others to do the same,” says Pisello.
The LEED (Leadership in Energy and Environmental Design) system is the most widely used green building rating system in the world. It examines energy use, water use, indoor environmental quality, material section and the building's effects on its site and gives building projects points for each element that contribute to a building’s overall ranking.
Another iconic building that has turned green is the Sydney Opera House. It was certified as carbon neutral in 2018 and was awarded a 5-star Green Star performance rating from the Green Building Council of Australia the following year. Along with its waste and water efficiency management programs and renewable power purchase agreement, the Opera House has installed an artificial reef along its sea wall to support marine biodiversity.
What can a retrofitting process entail? When it comes to existing and historic buildings, there are certain aspects and limitations to consider when the goal is to gain energy efficiency and decrease carbon emissions.
According to Pisello, the first step is the human aspect of the design – what are the needs and expectations in terms of comfort such as lighting, acoustics, air quality, and temperature. The next step is to consider all potential solutions aimed at reusing energy before incorporating new energy systems into the building. This can mean, for example, installing internal or external thermal insulation. After these measures have been taken, the process of designing integrated heating, lighting, and cooling systems can begin.
However, the architecture of a historic building can cause obstacles – or make it impossible to implement the hoped-for innovations altogether. Upgrading building operations systems might require changes that threaten the durability of the structure of the building and historic preservation laws can restrict or forbid changes to the exterior of historic buildings.
Then again, these buildings might have some advantages when it comes to hosting new technologies.
“For instance, underground floors that are not used anymore can be used for air conditioning and thermal systems,” says Pisello.
Energy efficiency retrofits are being designed through virtual reality, and new technologies are being developed to create better solutions for different types of needs. One of the most advanced innovations is photoluminescent materials that absorb radiation such as sunlight or even artificial light and then reemit the radiation to improve lightning conditions indoors.
“For example, I can put this material on my office windows, and during the day they charge with the sun. While working late in the evening, I still have the perception of enjoying natural light due to the radiation the material reemits, so I don’t need to turn on my artificial lightning,” Pisello says.
Despite all the technological advancements, there is still a lot to be done in terms of decarbonisation, and retrofits can play an important role.
“If we want to tackle climate change, we need to build less and focus on repairing old buildings. The best building project in terms of decarbonisation is the one where you don’t need to build anything new,” says Matti Kuittinen, an adjunct professor in the Department of Architecture at Aalto University in Finland.
The carbon footprint of even the most modern new building grows as more technology is put inside of it since the manufacturing of these products increases carbon emissions. This kind of embodied carbon is being widely overlooked in building projects while the focus is on energy efficiency.
“We should think about the total life-cycle of a building project. If we take all facets into account, at this point, we don’t have the technology to achieve total net-zero carbon buildings,” says Kuittinen.
According to Kuittinen, some retrofits can also be designed for bigger communities such as neighbourhoods, which could decrease the need for additional construction and reduce overall energy consumption.
Pisello also sees the need to look at the bigger picture. She says that the idea of energy communities could provide some answers.
“With all the complex new technology and the integration of renewable energy sources to reach zero energy targets, we have fallen behind from the net-zero carbon target. In terms of cost-efficiency and performance, sharing resources and making buildings work in more complementary ways could be the solution,” Pisello says.