Towards a performance-based approach for multifunctional green roofs: An interdisciplinary review

• Published in: Building and environment Vol. 188; p. 107489
• Main Authors: Cook, Lauren M., Larsen, Tove A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 15.01.2021; Elsevier BV
• Subjects: Albedo; Co-benefits; Design; Design optimization; Design parameters; Ecosystem services; Enthalpy; Evapotranspiration; Green buildings; Green roofs; Insulation; Interdisciplinary aspects; Interdisciplinary review; Irrigation requirements; Leaf area; Moisture content; Net radiation; Organic matter; Performance objectives; Roofs; Sensible heat; Solar energy; Solar panels; Stomata; Stormwater; Substrates; Sustainability; Sustainable design; Tradeoffs; Water balance; Water content; Water discharge; Design; Green roofs; Interdisciplinary review; Co-benefits; Performance objectives
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2020.107489

Green roofs have the potential to offer numerous ecosystem services; however, they are rarely designed to achieve them. Instead, design is restricted by perceived structural and maintenance constraints, which consequently diminish the achievable benefits. For green roofs to improve sustainability and resilience of cities, their design should match their promised multi-functional application using performance-based design. The first step towards a comprehensive performance model is to synthesize design recommendations across disciplines to identify synergies and trade-offs in design objectives for multiple benefits. This study discusses design strategies that could alter the energy and water balance in the green roof in order to attenuate urban stormwater, increase building energy performance, mitigate urban heat, and improve the output of solar panels placed on top of green roofs. These benefits are mathematically linked to quantifiable processes (discharge rate, water content, evapotranspiration, sensible heat, net radiation, insulation, and thermal mass), forming the foundation for a performance-based design model. Design recommendations are then summarized for each process, followed by a discussion of synergies, trade-offs, and research needs that arise when green roofs are designed to achieve multiple functions. Selecting vegetation with high leaf area and albedo improves multiple benefits without affecting structural constraints, whereas choosing plants with low stomatal resistance leads to trade-offs between higher evapotranspiration and higher irrigation requirements. Trade-offs in substrate depth and properties including organic matter and moisture are also apparent. Interdisciplinary collaborations are needed to simulate and optimize design parameters based on stakeholder preferences related to co-benefits and constraints. •Green roofs provide benefits for stormwater discharge and climate change mitigation.•Practical design of extensive green roofs do not align with expected co-benefits.•We quantify co-benefits by linking them to energy and water balance phenomena.•When optimizing for benefits, trade-offs and building constraints are important.•Stakeholder preferences must be considered when deciding on the benefits to pursue.