When considering thermal transfer capabilities, building façades pale in comparison to animal skin. Most buildings rely on passive strategies such as thermal mass or shading to mitigate temperature peaks, but animal skin is cooled effectively by multiple active strategies—one of which involves the dilation of blood vessels near the skin's surface in order to accelerate heat transfer to the surrounding air.
Scientists at the University of Toronto and Harvard University have taken note of nature's more effective cooling method, and have endeavored to develop a window that emulates this circulation-based heat transfer approach. Lead author Benjamin Hatton and his team created a water-infused glazing system with a silicone rubber layer containing a network of capillary channels. When filled with cool water, the capillaries readily lower the temperature of hot glazing. Moreover, the capillary network—which is visible when dry—becomes virtually invisible when wet.
The team's initial tests determined that such a system could reduce the temperature of glazing by 8 C (14 F), and that the energy absorbed would greatly outweigh the energy required to pump water into the system. With this positive news, the scientists are now studying the potential effects of installing the glazing on an entire building. The development of a comprehensive hydronic system of façade-based water delivery will not be without challenges, but the notion that buildings might cool themselves in a much more practical and proactive manner is a compelling idea.
Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.