Printing Living Walls

Abstract

Cities absorb and retain solar heat, intensifying the urban heat island effect at a growing cost to health and liveability. Vegetated surfaces cool their surroundings through evaporation, and mosses are well suited to colonising vertical surfaces, yet as poikilohydric organisms they cannot regulate or store their own water. During the summer heatwaves when cooling is most needed, an unsupplied moss layer dries out, falls dormant, and can leave a surface hotter than bare concrete.

This thesis develops a bioreceptive, 3D-printed porous ceramic facade tile that acts as an artificial vascular system, harvesting and storing rainwater and feeding it back to the biological layer by capillary action so the moss stays active through dry periods, while also providing a substrate for urban biodiversity. The work follows a Research-through-Design methodology across three scales. At the micro-scale, a white stoneware body was engineered with spent coffee grounds and corn starch as sacrificial pore-formers and fired at 1100 °C, producing a pH-neutral ceramic with an apparent porosity of about 39 % and a bimodal pore structure predicted to resist frost.

At the meso-scale, five printed surface geometries were compared for capillary uptake, moisture retention and rainfall capture, and a fractal-branching geometry showed the most promising combination, though single-sample testing makes the comparison indicative. These geometries were produced through a parametric pipeline in which a Python script generates the print toolpath directly and an interactive viewer lets each tile be previewed and exported for fabrication.

At the macro-scale, the validated tile was integrated, as a conceptual application, into a rail-mounted, gravity-fed module with an internal reservoir and a partial glaze that concentrates moisture in the porous zones where moss establishes. Outdoor testing showed the wet ceramic running far cooler than a conventional wall and staying close to air temperature through the day, which locates the cooling in the water-holding body rather than the plant; the glaze and the moss each give up a little cooling for a large gain in water retention. Transplanted moss established and has stayed alive for one month and seven days at the time of writing, healthy and still going, and a chamber test showed a single reservoir fill sustaining the module for roughly a day under worst-case drying, pointing to a larger store or passive rainwater buffering as the decisive step toward a genuinely self-sustaining facade.