World Green Roof Day – June 6, 2026

History of World Green Roof Day

If we are to believe the ancient texts, we can confidently trace the first green roof to the Hanging Gardens of Babylon, one of the seven wonders of the ancient world — planted in Iraq in 500 B.C. According to ancient Greek, Roman, and Assyrian texts, these gardens were grown over stone pillars and roofs. They were made up of trees and fauna found in the Babylonian mountains, and they supplied shade for people and cooled buildings’ interiors. Vikings also used green roofs during the Middle Ages to survive the harsh climate of their region. These green roofs were constructed using sod and grass, with substrates and water-retaining membranes made from birch wood. The roofs provide protection from harsh weather, good insulation during the winter months, and a cool interior in the summer. These Norse houses were so durable that their remnants are still found today.

Modern green roofing began in the early 20th century in Germany. The movement is said to have kick-started when Gerda Gollwitzer and Werner Wirsing published their book entitled “Roof Areas Inhabited, Viable and Covered by Vegetation.” In 1969, the movement gained traction when the government commissioned the construction of a green roof at GENO Pharmaceuticals headquarters. Green roofing expanded across Germany between the 1970s and 1980s as public interest in sustainable architecture grew, covering 13 million square meters by the mid-1990s.

In the United States, green roofing first appeared in the Rockefeller Center in the mid-1930s. It has since become part of the country’s social elements, with states such as New York and San Francisco offering tax incentives to developers who integrate green roofs in their buildings. Green roofs are found in most countries in Europe, Canada, the U.S., Egypt, and Costa Rica.