Green roofs in Vienna, Austria

General

National Id:

Austria_03

Site name:

City of Vienna

Summary:

Since 2003 the city of Vienna supports financially the implementation of green roofs with 8-25 € per m². The maximum subsidy can be 2200 €. Until 2010 16000 m² roof were transformed and 150 000 € invested.

The in-depth description of the case study:

cs-at-2-final_version.pdf

NUTS Code:

Wien

RBD code:

AT1000

Transboundary:

Data provider:

Sabine Tutte, ACTeon

Source(s):

„Logisch gedacht ist ökologisch bedacht" Ein Leitfaden für die Dachbegrünung

dachgrün

NWRM(s) implemented in the case study:

Green Roofs

Longitude:

16.373819

Latitude:

48.208174

Site information

Climate zone:

cool temperate dry

Mean rainfall:

500

Mean rainfall unit:

mm/year

Average temperature:

11,5

Mean runoff:

300

Mean runoff unit:

450 - 600 mm

Type:

Case Study Info

Light or indepth?:

In-depth

Average slope range:

1-20%

Vegetation class:

Depends on the individual project for intensive green roofs. Extensive green roofs consist of mosses and grass.

Monitoring maintenance

Monitoring impacts effects:

Monitoring location:

Edge of Field/Plot

Monitoring parameters:

During the project the retained amount of rain water was measured. Moreover, the pollutants removal was documented as well as the composition of plant and animal population. The temperature was recorded in the surroundings of the green roofs

Performance

Performance impact estimation method:

Catchment outlet

Performance impact estimation information:

Collection of the runoff from a green roof and a traditional roof during a precipitation event.

Biophysical impacts

Information on retained water:

The microclimate improves. That means: the increased evapotranspiration leads to an ambient temperature. The underlying rooms profit from this "natural air condition".

Water quality overall improvements:

Positive impact-WQ improvement

Information on Water quality overall improvements:

Rain water is filtered by the vegetation.

Information on Water quality Improvements (N):

Reduction by more than 90%.

Information on Water quality Improvements (Cu):

Reduction by more than 90%.

Information on Water quality Improvements (Zn):

Reduction by 16%.

Soil quality overall soil improvements:

Not relevant for this application

Lessons, risks, implications...

Key lessons:

Green Roofs are able to provide a lot of benefits such as climate regulation, water retention, or "island habitats" for plants and animals. These advantages have to be communicated more intensively to the public. Green roofs cause only little additional costs compared to a traditional flat roof. These costs are often compensated by the longer lifespan of the roof and energy savings

Success factor(s):

Type	Role	Comments
Attitude of relevant stakeholders	secondary factor	Many firms specialised on the construction of green roofs. They organised together with architects on national and european level to support the implementation of green roofs
Attitude of decision makers	main factor	Adaptation of the building code, information of the public.
Existing technical standards	main factor	Legal framework for the construction of green roof and liabilities of firms, architectures and house owners.
Financing possibilities	secondary factor	The local authorities support the construction of green roofs with 8-25€/m² and with a maximum of 2200€.

Financing:

Type	Comments
Local funds	Subsidies of the city of Vienna.
Private funds	Fortune of the house owner.

Barrier:

Type	Role	Comments
Expected maintenance needs	main barrier	House owners are often afraid that the installation of a green roof is combined with high costs. However this is not the case for extensive green roofs and the additional costs are often balanced by energy savings and the longer life span of the roof
Other	main barrier	Lack of communication. Citizens are not sufficiently informed about the many advantages of green roofs. The majority thinks, it is just another kind of garden
Missing regulatory support	secondary barrier	Architects/planners are liable for 30 years for the construction of a green roof. Since there is the risk that they aren't leakproof, architects partly refuse to consider green roofs in their plannings

Driver:

Type	Role	Comments
Legal obligations	main driver	Technical standard for building green roofs. The technical code of Vienna gives the legal framework for green buildings.
Availability of subsidies	main driver	The local authorities support the construction of green roofs with 8-25€/m² and with a maximum of 2200€.
Organisation committed to it	main driver	Both organisations inform the public about the advantages of green roofs. Moreover the Verband für Bauwerksbegrünung is composed of planers, architectures and specialised firms. They developed a certification system for green roofs and consult house owners and planners.

Financing share:

Share type	Share	Comments
Private funds		This depends on the individual roof.

Socio-economic

Direct benefits information:

Energy savings and a longer lifespan compared to a traditional flat roof. Savings meet the additional costs of implementation and maintenance.

Costs investment information:

0,31 Euros/m2 for extensive green roof with a slope less than 10° on a multi-family house with 7 floors.

Costs capital information:

0,31 Euros/m2 for the implementation of the green roof, without potetntial adaptation of the roof's statics.

Costs land acquisition unit:

€ (total value)

Costs operation maintenance:

0,19 Euros/m2 for an inspection twice a year, removal of growing trees, cutting grass.

Costs total information:

0,5 Euros/m2

Compensations annual information:

Financial support given by the city's authorities only once: 8-25€/m² up to 2200€.

Ecosystem improved biodiversity:

Information on Ecosystem improved biodiversity:

Green roofs can act as bridge between different habitats and populations. Birds find there material for building nests. Some observations even document that some ground breeding species take green roofs as new habitat. Insects find new food/habitat resources with the green roofs.

Ecosystem provisioning services:

Information on Ecosystem provisioning services:

Intensive green roofs can serve as garden and deliver fruits and vegetables.

Ecosystem impact climate regulation:

Impact on GHGs (net emissions and storage) including soil carbon

Information on Ecosystem impact climate regulation:

Vegetation stores CO² by photosynthesis. The increased evapotranspiration enhance dust adsorption, leads to an ambient temperature in the underlying rooms and takes up the summer heat of a city.

Policy, general governance and design targets

Policy description:

The more people are moving to cities, the more surface needs to be sealed and green areas are disappearing. In Austria 15 to 25 ha of usable ground get sealed every day. However green areas are important for recreation, mood lifting and health. Green roofs are a possibility to regain green areas and offer a manifold of advantages. A cadastre of potential roofs was developed. It proved that 20% of Vienna's roofs could become green roofs.

Policy pressure:

Policy requirement directive:

Policy impact:

Policy wider plan:

Policy area:

Policy target:

Target purpose
Oher Societal Benefits
Improved Biodiversity
Pollutants Removal
Groundwater Recharge
Peak-flow reduction
Runoff control

Design & implementations

Application scale:

City

Installation date:

2003

Lifespan:

Performance timescale:

< 1 year

Area (ha):

1,6

Area subject to Land use change or Management/Practice change (ha):

1,6

Design capacity description:

The water retention capacity of a green roof depends on several factors such as: intensity of a precipitation event, annual precipitation, and amount of precipitation events. Moreover the individual design of the roof (plant composition, soil type and thickness of soil layer) determines the water retention capacity.

Constraints:

Green roofs can be installed up to a slope of less than 45°. Intensive green roofs require an adaptation of the statics of the roof.

Favourable preconditions:

Lack of land, increasing sealing and thus in creasing amount of rain water.

Contractural arrangements:

Design contractual arrangement:

Design consultation activity:

Activity stage	Name	Key issues	Comments
Implementation phase	information material	in general the publicity for the project is not sufficient. It is criticised that people already have to know the term "green roof" to find information. The public don't know about the manifold advantages of green roofs. It is just reduced to a garden

Design land use change:

Design authority:

Authority type	Role	Name	Comments
Other	Other	1. Wiener Umweltschutzabteilung (city†™s authority for environmental protection)	Initiation of the project, subsidies for house owners
Other	Other	2. die umweltberatung	Facility of Vienna†™s adult education center. Consulting office for a near-natural life style. Publicity and information material
	Other	3. Verband fí¼r Bauwerksbegrí¼nung (Association for greening buildings)	Austrian section of the European Federation of Green Roof Associations
	Other		Publicity, implementation of green roofs, certification system for green roofs, Creation of technical standards

Last updated: 18 Jun 2015 | Top

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