The Greenfix retention box is used for temporary water buffering on flat roofs or underground parking decks designed for heavy loads. Rainwater is temporarily stored on the roof to relieve the sewer system, or retained for reuse in green roof applications. Depending on the application, this water will evaporate, be discharged in a controlled manner and/or be reused. This thermally stable retention box is available in various heights depending on the required water storage capacity. It offers high compressive strength, low weight and maximum water retention.