There is an answer for every question
Greening buildings is fully in line with current trends. Their performance and benefits can be scientifically measured. They can be implemented using quality assurance and standards. Despite of all this, there are lots of myths around green and living walls and green roofs. We provide answers to common questions. We are looking forward to receiving your questions, so that we can continue to extend our FAQ.
No. The construction cost of greening buildings is typically less than 2% of the total building construction cost.
No. projects show, that using intelligent planning, correct systems and vegetation, the cost can be below €12/m2 per annum. The larger the total area, the lower the relative costs. A lawn mown several times a year usually has relatively higher maintenance costs.
Yes. All climbing plants need care and nutrients. Costs for care and growth control of self-climbing plants can be reduced by putting in overgrow-barriers. Only one visual inspection per year is generally required to spot any health and safety risks, to cut back any growth and to remove any dead plants. Sensitive areas, such as windows, roof trusses, drains and gutters or similar need to be kept free of vegetation. Climbing plants using trellises or similar structures generally need less cutting back and do not grow directly on the building facade. Regular maintenance includes checking the climbing trellises, tying young climbing plants to the climbing frame after a storm and removing leaves.
Be careful! Depending on the complexity of the project or the used technology, we strongly recommend engaging an expert. This will help to avoid costly mistakes. Plants adapted to the location, how to use plants, the irrigation system, choice of material and system and transport all need to be planned well to ensure he longevity of the green building.
Definitely not! On the contrary, plant leaves move water away from the wall and plant roots take up water in their root area. The only exception is un unmanaged growth by ivy. The dead leaf material on the façade can lead to the creation of humous, which generates new soil within the wall. Green and living walls are installed in front of the existing façade and have an air circulation system between the green wall and the original façade. Elements containing water are always detached from the existing façade. An up to date study from the technical university at Vienna (KORJENIC et al., 2015) showed that assessed brickwork behind green and living walls is not moist, but dry.
This depends on the complexity of the project. The city of Vienna provides an administrative guide for greening building permissions and a simplified permission procedure to help and support you. Experts will be able to correctly asses the need for permissions and planning applications.
On the contrary – plants clean the air, capture dust and produce oxygen. The annual leaf litter can be easily removed in one work process, similar to trees.
This will depend on your priorities – water can be converted to evapo-transpiration cooling to improve the micro-climate. The electricity consumption for irrigation systems and LED illumination is generally very low. Considering that the production of one kilogram of beef requires 15,500 litres of water (WORLDWATCH INSTITUTE, 2004), any form of greening a building can be considered as highly sustainable, of high technical quality and with a high added value. Extensive green roofs and soil-bound green facades do not need any irrigation if intelligently planned.
The care and maintenance for green and living walls and green roofs, as well as interior green walls, should be carried out by a qualified company with the required business certificates (gardening and landscape architecture) and appropriate experience. It is never a bad idea to get several quotes.
The timber weight of fully–grown plants varies a lot. For example, clematis (10-30 kg), Wisteria (814 kg). When calculating the load this needs to be taken into consideration and the static properties may have to be assessed. For added insulation systems we recommend using a green façade with climbing plants on a climbing trellis in front of the original façade.
Definitely not with scientific proof provided. This prejudice may have arisen, because climbing plants have conquered some firewalls from the post war era and their adhesive organs are visible. The vegetation actually helps keeping the plaster on the wall. In addition, the ageing process of the plaster has been slowed down due to the protection from weathering. In comparison, fire walls without greening, need their facades replacing every 20 years.
When buildings are greened correctly, this does not increase the pest pressure. Greening buildings creates habitats and increases the abundance of birds and insects, which find attractive habitats around the building. You have to expect the breeding, nesting and feeding activities of for example wild bees and honey bees. Spiders on a roof tells ecologists: the tiger is back in the jungle! They tell us that the ecosystem is developing well. Good to know:
- Ants usually follow the water and are a good indicator for water damage
- Wasps like our food and are not interested in flowers
Aesthetics is a question of personal taste! When greening a building you always have a choice: you can use plants that shed their leaves in the autumn instead of evergreen plants. The former reflect the seasonal change of nature and can look attractive during the winter.
No. A damage of the building can only be expected when existing faults and damages are covered up by vegetation or the vegetation is not being removed professionally. Boston ivy, Parthenocissus tricuspidata, grows towards the light and does therefore not get into the building fabric. Plants that avoid light, such as ivy, Hedera helix, however, can grow into existing openings and expand them by the growth of their strong adhesive roots. Using ivy for greening buildings should only be considered after consultation with an expert. Growth barriers stop undesired growth. A regular control helps to avoid undesired developments.
On the contrary. A professionally carried out green roof installation increases the lifespan of the roof seal by at least 10 years! Green roofs are not more vulnerable to building faults than other flat roofs. Great care needs to be taken when selecting plants, as some types of plants have very strong roots and cannot be recommended for greening roofs. So, definitely involve an expert in the planning. If you do not trust the experience from many best practice projects, then you can of course use leakage monitoring systems and humidity monitoring technology as a fall-back option.
The weight of a green roof depends on the type of green roof. The height of the substrate layer or, in the case of a design with a mineral fill material, also the drainage layer is decisive.
Load assumptions water-saturated:
Extensive greening: from 90 kg/m²
Intensive greening: from 180 kg/m²
Solar green roof: from 110 kg /m²
If necessary, the surface load can be reduced by spot greening, often by the use of plant troughs or by differences in the level of the substrate. With special forms such as the light green roof (approx. 50 kg/m²), buildings that allow little superimposed load can be greened.
Extensive green roofs are considered as an effective ecological alternative to conventional roofs (e.g. gravel roof) where similar roof loads are to be expected.