Fa̤ade greening Рrelevance to building physics, systematics and standard-compliant implementation

Green fa̤ades do far more than just make an aesthetic contribution to urban design: they act as a natural protective layer for buildings, improve microclimatic conditions, bind fine dust, reduce sound reflection and contribute to the thermal relief of urban spaces. They also demonstrably increase the well-being of the population Рan aspect that is becoming increasingly important in building design.

However, professional and permanently functioning façade greening requires clear quality criteria. Structural integration must be regulated by standards and practicable. With the publication of ÖNORM L1136 in 2021, a Europe-wide standard for vertical greening is available for the first time. This standard supplements existing guidelines for roof (ÖNORM L1131) and interior greening and creates a systematic basis for the planning, construction and maintenance of vertical greening solutions in outdoor areas for the first time.

Systematization of vertical greening according to ÖNORM L1136

The standard distinguishes between five greening categories, each differentiated according to the physical structure and vegetation-specific interaction with the building envelope:

1. Category I – Ground-bound self-climbers
   This variant uses the plants’ own adhesion by means of adhesive disks or roots (e.g. Hedera helix, Parthenocissus tricuspidata). The prerequisite is an intact, load-bearing facade with a direct connection to the ground. The installation of overgrowth strips is recommended to control plant growth.
2. Category II – Ground-based greening with climbing aids
   Structured auxiliary elements such as ropes, trellises or nets are used for twining, climbing or spreading species. The substructure can be wall-mounted or free-standing in front of the façade. The soil quality must be adapted to the root space, water availability and nutrient supply.
3. Category III – Trough-bound green roofs
   These systems enable green façades without a direct connection to the ground. The plant troughs follow the multi-layer structure of intensive green roofs (drainage layer, filter fleece, vegetation support layer). Their construction must be UV-resistant, frost-proof and root-resistant. The integration of perennials, shrubs or climbing plants is possible.
4. Category IV – Wall-mounted systems with partial-area vegetation carriers
   These are suspended, rear-ventilated modules with their own substrate structure, usually designed as planted plant trays. These systems are intended for targeted, creative greening of smaller wall areas.
5. Category V – Wall-bound systems with full-surface vegetation carriers
   This form is the most technically demanding variant: Nonwoven or geotextile modules are pre-cultivated and installed on the façade, covering the entire surface. Automated irrigation and nutrient supply are indispensable components. The physical effect on the building includes a reduction in surface temperatures and an improved insulating effect thanks to the additional layer of air and vegetation.

Building physics significance and requirements

From a building physics point of view, green facades fulfill several functions:

• Thermal insulation: The greenery reduces the solar radiation on the building envelope and thus lowers the external wall temperature on hot summer days.
• Moisture buffering: Plants and substrates have a hygroscopic effect and contribute to the regulation of surface moisture and evaporative cooling.
• Sound insulation: Depending on the system type and plant density, sound reflections on the façade can be reduced by up to 10 dB.
• Air quality: Plants absorb COâ‚‚, bind fine dust particles and thus make an active contribution to improving the microclimate.

Categories of vertical greening
© GRÜNSTATTGRAU

Quality assurance and maintenance

ÖNORM L1136 defines clear requirements for planning, execution and maintenance. In addition to static and building physics verifications, regular maintenance cycles, pruning and control measures as well as professional irrigation system technology are required. Ease of maintenance is a key criterion for long-term operational reliability, especially for wall-mounted systems.

Care and maintenance of fa̤ade greening Рa key factor for effective building physics systems

The long-term functionality of fa̤ade greening stands and falls with proper care and maintenance. Despite this fact, the maintenance effort is often underestimated in practice or even seen as an obstacle during planning. However, especially in the context of building physics requirements Рsuch as thermal buffering, moisture protection or microclimatic optimization Рit is clear that only well-maintained greenery can develop its full potential.

Specific maintenance requirements for vertical vegetation systems

From a plant physiological point of view, facades are considered extreme locations. Low substrate volumes, wind loads, direct sunlight and the spatial distance from the natural soil require adapted care measures. These include

• Regular water supply, ideally through an automated irrigation system whose settings are adapted to the site conditions and plant species.
• Nutrient supply, adapted to substrate structure and vegetation requirements.
• Maintenance pruning, to maintain the shape, to control the incidence of light and to prevent overgrowth of technical equipment.
• Plant guidance, especially for climbing plants – for example by tying, rods or targeted growth guidance on climbing aids.

Close supervision is particularly necessary during the introduction and establishment phase.
ÖNORM L1136 clearly differentiates between different care phases:

• Visual inspections are used for the early detection of foreign growth, substrate problems or damage to components.
• Development maintenance (approx. 2 years): In this phase, the focus is on promoting the growth and structural stabilization of the greenery. This includes regular pruning, adjustment of irrigation control and manual watering as required in the event of extreme weather conditions.
• Maintenance care (from year 3): Long-term maintenance work such as the removal of dead plant components, the re-tensioning of climbing elements and the removal of leaf deposits ensure the structural effectiveness over the entire service life.

Technical and organizational requirements

Safe accessibility is essential for reliable maintenance work. Depending on the height and fa̤ade structure, suitable equipment (e.g. ladders, scaffolding or cherry pickers) may be required. The ease of maintenance of the greening systems must be taken into account as early as the planning phase Рfor example by integrating maintenance walkways, access points or remote monitoring devices for automatic irrigation.

Standards-based tools for planning, maintenance and documentation

ÖNORM L1136 provides application-oriented tools that significantly support the structured implementation and operation of façade greening:

A visual inspection form allows a uniform and comprehensible recording of the current condition of the greening elements – including plant vitality, technical equipment and possible defects.

The service level agreement defines the scope of maintenance, interval frequency per type of greening and qualitative requirements. It provides clarity about the expected services and supports the contractual arrangements between the client and service provider.

A sample schedule breaks down maintenance into clearly defined phases – from trial operation to development and maintenance – and provides practical guidance for operators and maintenance managers.

The positive effects of façade greening and green building envelopes as integral elements of climate-resilient urban development

The positive effects of greening buildings are the subject of intensive scientific research – well-founded and frequently validated research results are now available. These clearly show that green infrastructures on buildings are far more than just a design element – they fulfil a variety of functional tasks in building optimization and in the urban context.

Buildings can respond effectively to the challenges of climate change through targeted structural measures and strategically planned greening concepts. Façade greening in particular makes a significant contribution to this. Compared to conventional, ungreened façades, they influence both the immediate building environment and the building itself in several ways:

• Microclimatic improvement and enhancement of the quality of stay in urban areas
• Rainwater retention and relief of urban drainage systems
• Promoting biodiversity by creating new habitats in densely populated areas
• Compensation for ecological deficits, for example by replacing sealed or cut green spaces
• Thermal protection through shading, evaporative cooling and additional insulating effect
• Noise reduction through absorption and dispersion of noise sources on green surfaces
• Activation of vertical space reserves for multifunctional use – ecological, technical, creative