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Rooftop gardens, once a niche feature of luxury developments, are increasingly promoted as a practical response to urban heat and stormwater runoff. A layer of soil and vegetation absorbs solar radiation that would otherwise be reflected or re-radiated by bare rooftops, measurably lowering surface temperatures on hot days and reducing a building's cooling costs. During heavy rainfall, the growing medium retains a portion of the water that would otherwise overwhelm municipal drainage systems, releasing it gradually rather than all at once. Structural retrofitting is often required before installation, since older buildings were rarely designed to bear the additional weight of soil, plants, and retained water. Maintenance demands, including irrigation during dry spells and periodic replanting, mean rooftop gardens are rarely a fully passive feature once installed.