Intensive green roofs* are often associated with residential buildings, hotels or underground parkings. The more complex and heavier greening systems are characterized by a higher installation, maintenance, management effort (regular irrigation and fertilization) which leads to higher costs for the mentioned system type compared to extensive green roofs (chapter 3.2). Intensive green vegetation is often established on roofs that are accessible for public or recreation purposes and also for regular maintenance measures. The intensive green roof type is regularly frequented by humans: Different activities including gardening, relaxing and socializing are designated for intensive green roofs. To enable human activities on green roofs and the integration of larger plants, trees and architectural elements, suitable rooftops need to be relatively flat. The choice of suitable plants has to be greater (than on extensive green roofs) because of the different requirements and applications e.g. Aesthetic and ecological requirements. Appropriate plants for intensive green roofs are mainly trees, shrubs and perennials. The growth media is relatively thick and notably deeper than for extensive systems with integrated low-growing plants (see 3.2). The growth media of intensive green roofs needs to be relatively deep and nutrient rich to support the growth of plants or bigger trees. Beside a variety of plants, different kinds of architectural elements (buildings, solar panels) can be established on intensive green roofs.

*different terms for intensive green roofs used in literature are high-profile/ roof gardens (source: "Green Roofs." Provided in: Reducing Urban Heat Islands: Compendium of Strategies. Draft. https://www.epa.gov/heat-islands/heat-island-compendium)

Basic information

Type: 
Retrofitting + Creation

Performance

Evapotranspiration 2 2
Shading 1 2
Reflection (Albedo) none
Water Conveyance 2
Water Infiltration none
Water Retention 2
Water Storage 1
Water Reuse none
Water Filtering 1
Water Bio-remediation none
Deposition 1
Bio-filtration none
Habitat Provision 1
Connectivity 1
Beauty / Appearance 2
Usability / Functionality 1
Social Interaction 1
Role of Nature / Mode of Action: 
As illustrated in Fehler! Verweisquelle konnte nicht gefunden werden. the model for a green roof is atural soil with its vegetation cover. Through the establishment of (intensive) green roofs on buildings, different services of natural vegetation layers are replicated. As a result, the potential to mitigate the urban heat island effect is higher compared to sealed surfaces without any vegetation (black roof). Intensive green roofs can provide a variety of ecosystem services and benefits for the surrounding environment and microclimate. To enable these services, a natural, grown soil cover needs to be replicated. The vegetation layer absorbs solar radiation for photosynthesis. Large trees and plants covering the buildings surface and thus providing shade for resting user. Plants and trees as well protect from heat transmission into the building. Through the integration of vegetation, the 1) transpiration and 2) evaporation is increased (in comparison to black roofs), reducing the surrounding air temperature (=cooling effect). The retention of precipitation is a fundamental service of natural soils. Especially coarse-pored soils can store storm water for a longer period before it is transported into receiving water. A green roof temporarily stores rain-/wastewater, filters and binds impurities. The thick growing medium of intensive green roofs is positive in the context of water filtration, storage and water retaining.
Technical & Design Parameters: 
Different greening systems for intensive green roofs - and therefore no uniform construction - exist (a) substrate fill  substrate mix that varies in height on drainage layer (b) planters  substrate on drainage layer in plant Beside the mentioned systems other/special constructions for intensive green roofs exist. - plants: huge variety (trees, shrubs and perennials) - water requirement: irrigation necessary - growing medium: 6-15” (~ 15-38 cm) - slope gradient: flat, 0-5° (a-b) - weight: 190-680 kg/m (a); depends on plant and planters selection (b) - water retention capacity: 30-160 l/m² (a) - investment: 5 Euro/m²/cm substrate (a); > 500 Euro/m² - investment: median to high - maintenance: 3,50-5,00 Euro/m²a (a, b); medium to high
Conditions for Implementation: 
- site characteristics often depend on project objectives  e.g. objective = improving aesthetics; high density areas are preferred that are visible from surrounding buildings - solid, stable concrete buildings/bearing capacity - flat or relatively flat concrete rooftops and underground concrete structures - artificial irrigation but at least (rainwater) watering facility in critical/dry periods - in some cases special plates distribute pressure on rooftop are needed (for planters)
Benefits & Limitations: 
Benefits: - human health an quality of life - storm water/rainwater management and quality - improves air quality (reduction of greenhouse gas emissions) - aesthetic value/visual attractiveness - food production - additional space (intensive roof) - thermal performance/temperature reduction - energy reduction for buildings (heating/cooling) - reduction of noise/sound transmission - habitat provision for urban wildlife Potential limitations/disservices: - limited development of undisturbed habitats because of human activities/public purposes - limited spread of flora and fauna because of regular maintenance and management - limited space for rooting (although the growing media is relatively thick)

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 730052 Topic: SCC-2-2016-2017: Smart Cities and Communities Nature based solutions