How Should Cities Densify Buildings?
October 4, 2021
In conversations about mitigating climate change, one of the most advocated strategies is to densify. This includes reducing building footprint, freeing up ground space for greenery and preventing sprawl to untouched areas. At the same time, creating a mix of uses could improve the delivery of services with more efficient systems, cutting down carbon footprint from needing to commute to other places.
However, simply building taller and more compact neighbourhoods does not make a development automatically Greener. There are questions of embodied and operational carbon to reckon with. It can also be challenging to densify existing structures and neighbourhoods in a way that avoids carbon-heavy demolition while maintaining sensitivity towards the social and cultural fabric.
Above all—and this is most readily felt by inhabitants—the materials and systems used for tall buildings exacerbate the urban heat island effect, raising the ambient temperature by as much as 5 degrees Celsius compared to low-rise developments.
So, on the second day of the World Class Sustainable Cities (WCSC) 2021 conference, architect Serina Hijjas posed these key questions: Can we do densification differently? How do we reconsider aspirations for our cities to achieve density while being Green? And where can we have the most impact?
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Serina drew from the context of Malaysia’s affordable high-rise housing, which too often take the form of tall and bland boxes with little consideration for Green strategies. “Densification really relates to temperature rise, because we are increasing the amount of heat island around buildings,” she explained. As we get denser, we get warmer—and as a result we use more energy to cool down our spaces.
With more consumption, emissions are also increased. But this is not to say that the solution is to build more landed projects. Serina gave the striking comparison of the embodied and operational carbon in the iconic Fallingwater, which is roughly a third of the size of landed housing developments in Malaysia. In order to sequestrate or offset the total carbon emissions of three Fallingwater buildings, we need to build around 26,000 trees elsewhere, which would also take decades to fully flourish. As this is not easily viable, it shows the damage that one single construction already poses to the planet.
Thus, what constructions can do is change the way we currently densify. “Not by using industrial technologies designed in war, but nature-based technology and design made for peace,” she encapsulated. In the tropical context, we could make a big difference by densifying using materials with lower embodied carbon such as sustainable timber and eco-concrete, switching to emerging low-carbon technologies such as carbon capture, and maximising passive strategies to cool down our spaces.
“Cooler buildings go beyond Greening buildings,” she said, presenting concepts for cooler and more liveable vertical cities. Studying horizontally stacked building forms such as Moshe Safdie’s Habitat 67 and OMA’s The Interlace, Serina believes that this passive building strategy could achieve the required density while also bringing buildings closer to the ground, reducing the heat island effect. Moreover, in a scheme that flipped upside down the pyramidal shape of Habitat 67, the mass was able to self-shade and cool inner spaces, creating a green canopy out of its own form.
Next, densifying cities would need governments and businesses to also be motivated to achieve this idea of cooler, Greener buildings. “First of all, we have to recognise that this is the only way forward.” Until the current paradigm of building is shifted, designers will continue to face huge challenges. The largest concern on the ground is that this will cost more in terms of return on investment—further reducing demand for sustainable materials and technologies, deadlocking industry players who want to achieve low-carbon goals. Thus, the first step comes with recognising that this goal needs to be addressed on the government level, and continually empowering choices that can improve the lives of citizens as well as the health of the planet.