A small town affected by climate change
How do buildings affect and interact with each other? How comfortable are people in the world’s cities, which are growing both physically and demographically and consume 75% of the world’s energy? It turns out that the EPFL campus is the perfect testing ground for getting a sense of how cities work and identifying long-term solutions. Wind, heat island, thermal bridges, paved and unpaved surfaces, microclimates - the campus has it all. This makes it ideal for conducting an in-depth analysis of energy demand in buildings and how this correlates to human comfort in the outdoor environment.
Human comfort is not a new topic of study for researchers. Given its complexity, however, architects and urban planners do not find it easy to incorporate into their work. "We can quantify thermal and visual comfort inside buildings, but it’s very difficult to do the same outside," says Silvia Coccolo, a researcher at EPFL’s Solar Energy and Building Physics Laboratory (LESO-PB) who wrote her PhD thesis on this topic. "We can start by looking at where people like to walk around and sit, where they are naturally drawn to, in order to see whether a given site is comfortable and, if so, during what time of the year - since this can vary with the seasons." Coccolo continues: "Two important aspects are taken into account when quantifying thermal comfort: the energy balance between the amount of heat absorbed and emitted by the body, and psychological perception, which is a subjective sensation."
Coccolo identified dozens of microclimates at EPFL, which are the product of the campus’s urban and environmental design; the Avenue du Tir-Fédéral is a wind tunnel, while the Rolex Learning Center, with its unique architecture, creates irregular temperature fluctuations and air currents. The Dorigny forest, which is very popular in the summer, also plays an important role in the local climate. "Sitting in the new Place Cosandey is not at all like sitting at the SwissTech Convention Center: on the same day and with the same air temperature, you feel totally different in both places."
Coccolo sought to determine how the EPFL campus architecture should be adapted as the climate changes. Worldwide temperatures are expected to rise by 1.5 degrees, as announced at the 2015 Climate Change Conference in Paris. However, ambient temperature readings in the alpine region are rising twice as fast as the global average. The researcher’s first step was to assess the campus’ energy balance; she looked at individual buildings and the effect that buildings have on each other. Summers will be hotter and hotter, and this will be felt more in built spaces than in wooded ones. Existing buildings will have to be renovated, and new buildings will require design changes. Particular attention will have to be paid to the exterior of buildings: "Vegetation moderates microclimates and blocks solar and infrared radiation, evapotranspiration reduces the air temperature, and plants provide shade," says Coccolo. "These factors completely change our perceived thermal comfort."
Turning climate challenges into design opportunities
To offset the expected rise in summer temperatures, the study shows that, in addition to proper insulation, buildings and their immediate surroundings will need to provide more shade through protective features according to the level of solar radiation, the direction the building faces and the season. For Coccolo, this goes beyond simply multiplying the number of plants and trees; the focus should be on what truly enhances comfort. This may include such things as foliage density and plant height. Replacing asphalt with grass, for example, can radically change our thermal perception.
The Urban Systems group at the LESO-PB believes that, in the future, architects and urban planners will need to work together in designing the space between buildings, which is just as important as the space inside them (leso.epfl.ch/urbansimulation).