In Conversation with Philippe Rahm: A Climate-first Approach to Architecture

Although it can be difficult to envision Earth’s temperatures before our lifetimes, climate proxy data¹ over the past 2,000 years shows that we are living in a thermally unprecedented era. Over the past two centuries that correspond with industrialism, average global temperatures have been on an anomalous rise, to the point of surpassing the 1.5 degrees Celsius threshold in 2024.² This seemingly small degree may pose cataclysmic consequences—be it in the increasing severity of meteorological disasters or the effort it would take to modify our microclimates to support life on Earth, something that people may take for granted.

FuturArc spoke to Philippe Rahm, principal of Philippe Rahm architectes and tenured associate professor at the National Superior School of Architecture in Versailles, France. Since the 1990s, his work has championed architecture’s physiological and meteorological aspects, exploring design approaches that dynamically interact with climate as ‘building blocks’ of architecture. As highlighted in recent lectures across Asia to introduce his latest book Climatic Architecture (Actar Publishers, 2023), Rahm continues to advocate architecture that is rooted in historical and socio-cultural contexts while addressing the urgent challenges of the present.

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DESIGNING IN A ‘TOXIC’ ENVIRONMENT

DM: For places like Indonesia, Thailand, Singapore and Malaysia, air pollution is a major problem that has been increasing in recent years, exacerbated by the climate crisis sparking forest fires and the continued usage of unclean power sources. This has thus shifted our rule of thumb in tropical design, where ideally, we should let in as much ventilation as possible, but which we cannot do so now since we have to protect ourselves against the ‘dirty’ air.

In your Taichung Central Park project, to tackle a similar problem in Taiwan, you suggested to control the air flow and use certain plants to absorb some of the pollutants. However, there have been various studies that showed how trees could actually increase the amount of local pollutants, because the particulate matter gets ‘stuck’ and makes the surrounding air dirtier.³ What do you think can be done for this problem—when the ‘building blocks’ of climate become toxic?

PR: Air pollution has two meanings—toxic pollution, like gases and particulate matter (PM) that damage your health when you breathe them in; and CO2 pollution, where it is blocking the infrared from the Earth and creating global warming. For the second type, the increase is everywhere on the planet, made worse by the burning of fossil fuel and such. In Europe, for example, now the climate is becoming increasingly warmer like in North Africa or Indonesia. This is why we should fight to lower the emission of CO₂ first, by stopping the use of fossil energy as our primary mission.

What you are describing is true. In the beginning, we saw studies that showed how some resinous trees (that have a kind of glue on them) could be used to capture PM_2.5, and some plants with hairy leaves. But once there is rain, everything falls down and could go back in the air. So, in reality, very little is captured.

The difference between day and night temperatures …
is disappearing, making passive cooling methods
increasingly difficult to apply.

In Milan, we did a project with Koolhaas of OMA where we wanted to clean the air. We proposed creating artificial rain, because when there is a lot of airborne particulate matter, the rain is expected to ‘clean’ the air since all the PM_2.5 and PM₁₀ will go into the ground with the rainwater. So, our proposal will have the double effect of cleaning and cooling the air. But you will need water to do that, so it depends on the climate. And you need energy to activate the (fake) rain, so it will have to come from photovoltaic panels or renewable energy for the pumps.

Architecture is a kind of artificial construction of microclimate, whether you are doing a wall or roof to shield yourself against the rain, so we have to extend this way of thinking about architectural design as some modification of the macroclimate to find new solutions. To create new shadows or winds, we can imagine doing them carefully, without using a lot of energy and without emitting CO₂.

The South’s climate is moving to the North. Parts of the world could become uninhabitable because it will be too hot and maybe too humid. For the human body, it will be very complicated to survive in this type of climate.

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DM: There is a problem that will haunt us in the near future, which is ‘global boiling’ as both ambient temperatures and humidity increase to reach wet-bulb thresholds.^4,5 When the sweat from our bodies cannot evaporate, there can be fatal consequences for the human body. What do you think will be most urgent for us to do to address this?

PR: When the air temperature is higher than 35 degrees Celsius, which is the skin’s temperature, the only way of cooling the body is through perspiration—sweating and evaporating water. But if the air is already saturated with water vapour, you can no longer lose heat and in a few hours you could die.

For Taichung Central Park, we tried a device to reduce humidity by using silica gel, which can absorb water vapour but still requires energy to dry. So, it became a complicated machine. You can do that with renewable energy, which maybe in the future we can have, because it will be the only way we can survive.

The machine for the park was a little complicated because it was very technological and some of the people were not ready for this type of complication, especially because it needs maintenance and there are issues of obsolescence. Passive solutions would be better, but sometimes, it may be quite challenging to find.

[This is an excerpt. Subscribe to the digital edition or hardcopy to read the complete article.]

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Read more stories from FuturArc 4Q 2024: Tempering Temperatures!

¹ National Oceanic and Atmospheric Administration, National Centers for Environmental Information (NCEI), “What Are Proxy Data?” https://www.ncdc.noaa.gov/news/what-are-proxy-data
² World Meteorological Organisation, “Global temperature is likely to exceed 1.5°C above pre-industrial level temporarily in next 5 years”, 2024 https://wmo.int/news/media-centre/global-temperature-likely-exceed-15degc-above-pre-industrial-level-temporarily-next-5-years
³ Tom Grylls, Maarten van Reeuwijk, “How trees affect urban air quality: It depends on the source”, Atmospheric Environment, Volume 290, 2022, 119275, ISSN 1352-2310, https://www.sciencedirect.com/science/article/pii/S1352231022003405. “Abhijith et al. (2017) … reported that on average, across all studies considered, trees had a detrimental effect (≈20–96% increase in local pollution concentrations). Buccolieri et al. (2018) reiterated this viewpoint in stating that whilst the problem is highly case-specific, in the majority of cases the reduced ventilation and increased drag induced by trees outweighs their active removal of pollutants from the urban atmosphere.”
⁴ “Explainer: How is climate change driving dangerous ‘wet-bulb’ temperatures?”, Reuters, 2023, https://www.reuters.com/business/environment/how-is-climate-change-driving-dangerous-wet-bulb-temperatures-2023-08-09/
⁵ Warren Cornwall, “Lethal levels of heat and humidity are gripping global ‘hot spots’ sooner than expected”, Science, 2020, https://www.science.org/content/article/lethal-levels-heat-and-humidity-are-gripping-global-hot-spots-sooner-expected