Passive evaporation of water reduces a building's cooling energy demand. However, water is often wasted due to rebound, uneven spreading, and rapid drainage. Here, we present an elephant-skin-inspired crack network architecture in porous diatomaceous earth (DE)-cement composites to capture, route, and store water with minimal runoff. DE's micro/nanoporosity enables ultrafast (sub-50 ms) water imbibition, while crack networks act as capillary conduits that redistribute water across and up inclined surfaces. Substrate-guided stress concentration converts drying-induced stochastic fractures into deterministic crack lattices that route and retain water on inclined surfaces, enabling geometry-tunable, water-efficient evaporative cooling. Tiles of hexagonal lattices with intermediate crack density maximize lateral redistribution and delay drainage. Infrared imaging reveals edge-dominated evaporation, sustaining prolonged cooling. In a mockup home model covered with DE-cement tiles, under repeated water dosing and IR heating, the temperature beneath the DE-cement tiles is maintained at ∼32°C vs ∼42°C and ∼52°C for cracked and non-cracked commercial stucco, respectively. The study offers a simple, scalable route for passive cooling.
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