We had the privilege of participating in the 2024 ACAW Workshop in Buffalo, NY, last month with our friends and colleagues from Behnisch Architekten, KnippersHelbig, and TriPyramid. ACAW, which stands for Architectural Ceramics Assemblies Workshop is organized by Boston Valley Terra Cotta. The workshop was an incredible opportunity to push the boundaries of innovation in terra cotta façade design. This project began earlier this year when Behnisch approached us with the challenge: What’s the biggest problem we can solve with an opaque façade tile design?
Opaque façades play a crucial role in well-insulated thermal envelopes. So, we asked: what should be the main performance driver for such a design in the context of climate change and urban environments? As our teams live and work in dense cities like Boston and NYC, we wanted to address a major urban issue— the urban heat island (UHI) effect. UHI is a growing problem, exacerbated by climate change, where city temperatures remain higher due to retained heat in built environments. Temperatures drop quickly as we move away from the city to more rural areas.
For us at Transsolar, it’s clear that a major contributor of UHI is the amount of thermal mass in cities that heats up, has limited radiant heat loss to the sky and retains heat for longer, therefore affecting overall outdoor comfort day and night. Could we use water and reflective glazes to block solar gains and cool the surface of the tile with evaporation? The aim was to design a terra cotta façade system that mitigates UHI locally, to improve outdoor comfort in cities that rely on pedestrian use and outdoor public spaces.
Behnisch was very passionate about creating a tile that was practical and rooted in the vernacular building practices of the northeast, as well as addressing the issue of UHI effect for their immediate neighborhood in Boston’s Chinatown. Their inspiration was the Cape Cod shingle as a rainscreen for manufacturing and installation ease. From our end, we decided to use water to cool the tiles, and the design driver was how to channel the water, delay the movement through the system, absorb it, retain it and evaporate it to reduce the surface temperature of the façade, all while being careful with the freeze-thaw issues of our cold winter climate.
We worked closely with Boston Valley Terra Cotta to design three types of tiles: a screen tile for shading building apertures, a shingle tile to slow down the rate of water in the façade and guide it to lower areas for evaporative cooling, and an evaporative cooling tile located at the pedestrian level with higher surface area for more water absorption and evaporation. We wanted to affect the surface temperature of the façade, and how that will have an impact on the mean radiant temperature of pedestrians or people occupying the street. This process took various physical tests and iterations before building a one-to-one mockup in August.
We built a full-scale mockup of the design and found that we could cool the tile surfaces by 10°C (18°F) from air temperature, reducing the mean radiant temperature of the sidewalk environment by 3 to 5.5°C (5 to 10°F). More details of our work and design will be shared in the future publication by Boston Valley Terracotta. Find our presentation here >