Sustainable built environment
Green Roof
A roof system layered with growing medium and vegetation that retains stormwater, insulates the building, cools the city, and creates habitat.
Definition
A green roof is a roofing system incorporating vegetation, a growing medium, and drainage over a waterproof membrane, designed to capture and retain precipitation on the building. Systems are classed by depth and planting: extensive roofs (typically up to about 15 cm of medium, lightweight, low-maintenance, drought-resistant plants such as sedums) and intensive roofs (deeper substrate supporting shrubs and trees, accessible as gardens but heavier and maintenance-intensive).
References
typology and performance
system types
Overview
What it means
Green roofs address several urban problems at once: they retain a large share of rainfall — research suggests around half or more can be captured and returned to the atmosphere — reducing runoff peaks; they insulate and protect the membrane, extending roof life; they mitigate the urban heat island effect; and they provide habitat and amenity in dense areas.
How it is used
Cities incentivise or mandate green roofs in stormwater and building codes; designers specify them as stormwater best management practice and for building certification credits.
Why it matters
Roofs are a large share of urban impervious surface; greening them is multifunctional climate adaptation that needs no extra land.
Review
Public comments appear only after editor acceptance. Draft comments stay in the review queue.
Reviewers choose the definition or an overview paragraph, leave a comment or replacement, and attach evidence or a source link.
Editors compare reviewer cards side by side. AI may help find agreement, conflicts, unsupported claims and possible source issues.
Only an editor-accepted synthesis changes the public page. Reviewer identities are shown only with consent and an editorial decision to attribute them.
Submitted reviews stay private until an editor decides whether to accept and attribute them.
Contribute to this entry
Help improve this definition
Your contribution is private while it is checked. Nothing changes on this page unless an editor accepts it.
Loading verified endorsements… Endorsements are not votes and never determine publication.
Endorse this definition
Endorse the exact version shown here. This is not a vote, and publication remains an editorial decision.
Review board
Comment on a specific line. Each reviewer stays separate until an editor accepts a merged draft.
Each person comments on the definition or overview in their own draft card, with role, evidence and suggested wording kept together.
AI can compare comments against the current text, flag conflicting claims, surface missing evidence and identify where reviewers agree.
An editor merges compatible suggestions into a draft change, checks sources, records disagreements and decides what can be published.