Abstract

Green roofs have been proposed as an efficient and practical tool to combat urbanisation in many countries. This review paper focuses on various benefits associated with green roofs and research efforts made till date to promote green roofs. Through systematic comparison of literature, this review also emphasises knowledge gap that prevail in green roof technology and highlight the need for local research to install green roofs in developing and under-developed countries. Considering that growth substrate, vegetation and drainage layer determine the success of green roof, efforts were made to consolidate desirable characteristics for each of these components and suggests methodology to construct practical green roofs. This critical review also explores limitations associated with green roofs and recommend strategies to overcome. Apart from stand-alone green roofs, there is a huge scope for hybrid green roof systems with other established techniques, which are presented and discussed. Recommendations for future study are also provided.

Introduction

Rapid economic development and demographic shifts have fueled intense urbanisation across much of the world. As cities expand vertically and horizontally, urban green areas often shrink, replaced by buildings, pavements, and infrastructure. This transformation tends to reduce vegetation cover and canopy interception, restrict evapotranspiration, and exacerbate the urban heat island effect. Combined with diminished air humidity and altered hydrological cycles, such changes degrade urban livability.
Amid these pressures, the unused rooftop surface of buildings has emerged as an under-utilized resource. Converting conventional roofs into vegetated or “green” roofs provides a promising path to reimpose ecological functions back into urban fabric. A green roof (also called a living or vegetated roof) typically places a growth medium and plant cover above a waterproofing membrane. Well engineered systems also include drainage, root barriers, and filter layers.
Over the past few decades, green roofs have gained traction in many countries—especially Europe, North America, and parts of Asia—owing to their ability to deliver multiple ecological, economic, and social benefits. Yet significant challenges remain: the optimal configuration of design components (substrate, vegetation, drainage), the adaptation to local climate and structural constraints, and the need for robust empirical studies—particularly in developing nations where climatic, economic, and technical contexts diverge.
This review attempts to (1) distill and categorise the benefits and performance outcomes from existing literature, (2) identify current gaps and barriers to broader adoption, (3) present best practices for component selection and system design, and (4) discuss potential hybrid systems and future research pathways. Throughout, the emphasis is on relevance, practical applicability, and optimizing performance outcomes for diverse climates and built environments.

Introduction

Rapid economic development and demographic shifts have fueled intense urbanisation across much of the world. As cities expand vertically and horizontally, urban green areas often shrink, replaced by buildings, pavements, and infrastructure. This transformation tends to reduce vegetation cover and canopy interception, restrict evapotranspiration, and exacerbate the urban heat island effect. Combined with diminished air humidity and altered hydrological cycles, such changes degrade urban livability.
Amid these pressures, the unused rooftop surface of buildings has emerged as an under-utilized resource. Converting conventional roofs into vegetated or “green” roofs provides a promising path to reimpose ecological functions back into urban fabric. A green roof (also called a living or vegetated roof) typically places a growth medium and plant cover above a waterproofing membrane. Well engineered systems also include drainage, root barriers, and filter layers.
Over the past few decades, green roofs have gained traction in many countries—especially Europe, North America, and parts of Asia—owing to their ability to deliver multiple ecological, economic, and social benefits. Yet significant challenges remain: the optimal configuration of design components (substrate, vegetation, drainage), the adaptation to local climate and structural constraints, and the need for robust empirical studies—particularly in developing nations where climatic, economic, and technical contexts diverge.
This review attempts to (1) distill and categorise the benefits and performance outcomes from existing literature, (2) identify current gaps and barriers to broader adoption, (3) present best practices for component selection and system design, and (4) discuss potential hybrid systems and future research pathways. Throughout, the emphasis is on relevance, practical applicability, and optimizing performance outcomes for diverse climates and built environments.