Based on practical experience … information on the successful realisation of facade greening
Talk by Thorwald Brandwein at the 2. FBB symposium about facade greening on 29.09.2009
From „traditional“ to „innovative“ facade greening
- Remarks on history
- Current practices
What does successful facade greening look like?
- Effort, benefit, costs
- Economizing and prospect of success (example)
General recommendations for the successful realization of projects
- Incentive – Advertising, information, examples
- Quality management
- Funding – promote longevity
Details on the successful realization of durable facade greenings (traditional approach)
- Aspects of planning
- Climbing plants
- Facade constructions and wall constructions
- Climbing supports and fastening to facades
General views on traditional and „new“ facade greening in regard to successful realisation
I would like to thank you for the opportunity to speak in the context of this interesting event about facade greening. I want to offer an insight from the point of view of a practitioner, who is convinced by the great potential of “vertical gardens”. However, I have to admit that the practical significance in regard to urban development in Germany is still (or again) a weak point. Particularly façade greening projects that could have a direct, positive effect on urban life are not often realized successfully – in any case, not sustainable enough in my judgment.
At the risk of preaching to the choir I will dedicate one part of my talk to the presentation of „non-technical“ rather economical „development problems“ that hinder recent greening projects, especially in Germany. One reason might have been the local climate or the impression that already enough has been done concerning facade greening. However, facade greening is booming and spectacular projects are realized all around the globe from Canada to the Gulf States to the Far East to Australia. Thus, it should also be possible in this country (Germany). After all, a considerable amount of expertise – especially in recent decades – has been acquired in Germany. A majority of the published professional literature is written in German and is groundwork for recent projects all over the world.
It is important to me to contribute that the already existing knowledge is used to realize successful projects of facade greening – especially in a urban environment.
From „traditional“ to „innovative“ facade greening
The use of climbing plants dates back a long time ago. A pictorial figure of wine producing in Egypt is about 3600 years old (Tomb of Nakht).
The date the first time exterior facades were improved in any way by the use of plants, so that one could speak of facade greening probably remains unknown. But there are hints that tend towards early beginnings. In Japan thousand-year-long wisterias indicate an early garden art with the utilization of woody climbing plants. The rather legendary „Millenial Rose Tree“, located at the cathedral in Hildesheim, is traceable for about 400 years. But no one can refute the popular date 815. With the import of several climbing species to Europe, a standard evolved in the last centuries that can be referred to as „traditional“ solutions for facade greening.
However, the latest, most interesting developments in facade greening are considerably younger. In the last decades the development of facade greening kept up with the one in city planning and constructional engineering – also when the visual cityscape suggests something else. At the same time products were devised that can optimize the potential of green facades in cityscape. But I think that greening possibilities that are currently available, even the most approved ones, are used far too rarely in practice. The more dense a city is build, the less greening opportunities are used.
Current Practices (methods for greening exterior walls)
New methods for greening exterior walls, that no longer require climbing plants or espaliers, expand the possibilities and will contribute solutions to ecological problems as well as to urban construction problems of existing and growing mega cities. Even cities that are still manageable (cf. image3), require more comprehensive facade greening than the ones that are still common in practice to date. At the moment we are experiencing the step towards „living walls“ and „vertical gardens“ or „wall-sprouting“ as i call this type of facade greening (image 4).
With the development of suitable alternatives to plantings in the soil or big containers, exterior walls become areas of where plants can grow. Whereas facade greening with climbing plants requires the mounting in front of a complete constructed exterior wall (supporting framework, insulation, rear ventilation if applicable, weather protection) vertical vegetation systems can be installed as curtain wall facades that are rear-ventilated. Rear-ventilated facades provide the opportunity to replace an expensive facade due to their versatile outer layer (vegetation, substrate containing cassettes, tilings, fleece). Insulation, rear-ventilation and sealing can be properties of such a system of facade greening.
Such and similar techniques will result in an immense increase of planting possibilities, especially concerning new buildings. Thus vertical areas are theoretically no longer subject to „restricted greening“ but increasingly offer the same possibilities like horizontal areas (image 6).
Whereas traditional façade greening is naturally limited concerning the realizable height of greening, vertical vegetation decreases the demands on dimensions of the chosen non-grounded plants. The use of smaller plants additionally simplifies the prevention of unwanted spread on areas that are not designated for greening. When and how such expectations can be seen as generally applicable and when they can be transformed into good results is not yet fixed. Considering the so far realized greening-heights that are provided by the new methods (vertical gardens / living walls) there is no significant advantage in performance in comparison to traditional facade greening yet (image 7). However it is possible to realize a greening of a large area in very short time (minimal growth period) if the technical construction takes into account climate and exposure.
In practice, even the traditional, also termed classical facade greening – is still often considered accessories to buildings and does not come close to utilizing the actual capabilities. The more recent methods also need time until they could perform like current enthusiastic reviews suggest. No facade greening project works without real commitment and true expertise.
What does successful facade greening look like?
In a nutshell: If the result meets the targeted gain and expectations. An appropriate relationship of cost and effect is desirable. The targeted goal of a greening project has to be achieved and maintained by a reasonable amount of effort. Since the goals of greening projects cannot be generally converted to monetary value, the benefits of facade greening are unfortunately rather difficult to convey to building owners. The cost factor on the other site is always well documented. From a point of view that is concerned with profitability, the monetary value of a greened facade should outweigh the expenditure. That is hardly possible because several positive effects benefit the environment and cityscape more than the greened object itself. Thus, costs for manufacture and maintenance of facade greenery become automatically a kind of „additional social and environment levy“. It may sound provocative to say that the majority of all bigger projects are being stripped of adequate financial support right from the start. In my experience that’s rather only half the story. The benefit of cheap, inexpedient solutions is likely to fall by the wayside because of shortcomings in maintenance. In this case one can be „happy“ if the shortcomings did not leave behind serious damage to the structure.
A real-world example:
A greened parking block in Monte Carlo, greening system „Hecke am laufenden Meter“ (image 8).
Apparently the result was very pleasing, so that the retaining wall to the right was also to be equipped with a climbing system – but without the complete know-how of Dutch and German specialists. The result of the greening of the „replica“ is significantly worse than the original and proves, again, that costs cannot be reduced boundlessly if a high quality standard is desired.
Needless to say that the more expensive solutions are not automatically the better ones but in order to achieve goals, like the improvement of city atmosphere and climate, as well as the reduction of energy consumption and fine dust pollution, there has to be the will to adequately invest in such solutions. No one should be expecting high-value results if there is no one willing to pay for it.
Before the quality of a project is compromised in order to cut down costs, the project’s specific standards concerning cost and effect should be reviewed. The greened environment in Monte Carlo is also an example demonstrating alternatives which don’t compromise the quality of a greening project. At the same wall, about 50 meters to the west of the greened façade (system: “Hecke am laufenden Meter”; to the east: the inferior “replica” complementing the original system) we find a good maintained greening project with climbing plants (Bougainvillea) representing the traditional approach of façade greening (image 11).
This project, carried out in the “traditional“ way, may be about 20 years old but is still decades from obsolescence. The surrounding planters will have to be replaced or newly planted within the next 12 to 15 years because of the increasing root size. The vegetation in the area of the replica system (can’t be seen in image 11) is not likely to achieve a similar life expectancy. The foreseeable need for renovation considerably lessens the benefits of the both newer, “more innovative” approaches. On the other hand the features of those systems (here: “green immediately, “automated supply and disposal” and “no required space on the ground”) are quite handy and might even be a requirement for the operability of a greening project.
Which of the three approaches is most likely to be successful?
At first view the traditional approach is the best, the most successful one, even though it might be visually monotone. Its system in a plant bed with minimalistic climbing aids (horizontal square profile metal rods) was a lot more cost-effective compared to the other solutions. This approach is also superior in terms of vitality and area-covering of the vegetation – however, I don’t know the duration of the growth period and intensity of maintenance during that time. Currently there is at least a maintenance once a year during which a majority of the blossoms are cut. This small disadvantage of repeatedly flowering climbers is (depending on climate) hardly to be inhibited but it should not be a persisting problem. Usually it does not take long until a greened wall is in flower again, thus becoming visually diversified and appealing (image 12).
There are also compelling arguments to consider the other approaches as a success. When we look at the buildings above the greened wall in image 10, 11 and also consider various other cityscapes, there is an obvious demand for facade greenery of high buildings. It would not be possible to completely cover such a large area with vegetation, not even in six or seven years by using grounded plants or planters. So maybe there is a long-term advantage in choosing the considerably more complex and costly approach which also offers an “immediate greening”?
In every case the conclusion is that the choice of appropriate, competent, project specific and reliable greening methods is the cornerstone for success in facade greenery.
Successful façade greening is also a general question of quality. Quality protection (which I will talk about in a moment) ensures success.
General recommendations for the successful realization of projects
Setting the direction for a successful realization of projects begins way ahead of any concrete project work: the motivation of potential building owners.
Incentive – Promotion, Advertising, Information, representative examples
Fancy flyers, merely verbal ecopolitical initiatives and happy home owners in front of amateurishly executed façade greenery contribute little to the goal of motivating. Such advertising initiatives often convey the impression that the privatization of costs are more important than the quantity and quality of city greening. Nothing less than counterproductive is the process of greening and “de-greening” facades of the Honnefer town hall in Bad Honnef. After the cheaply greening turned into a faulty “monster” which cost 14000 euros a year for maintenance the decision for a clear-cutting was made.It’s hard to imagine that a project like that and its execution did not raise questions earlier from various positions. Especially public institutions should create reference objects and be able to maintain them. Local politics, planning offices and building authorities should not only make façade greening mandatory for newly constructed buildings but also control the execution of a project according to guidelines and ensure the continuance of greening projects.
Quality protection for greened facades
The next step for successful facade greenery is an interaction between building owners, planers and contractors in order to choose and maintain quality standards for planning, tendering, execution and maintenance according to the requirements of the respective project.
The observance of “Guideline for planning, execution and maintenance of facade greenings with climbing plants” (german: Richtlinie zur Planung, Ausführung und Pflege von Fassadenbegrünungen mit Kletterpflanzen) (FLL) ensures appropriate standards for this task as long as the recommendations for the choice of plants are actually used. If instead the focus is almost only on low-cost solutions, the planting and even the structural/architectonic circumstances are often neglected, usually resulting in unsuccessful projects. Such practices delay and hinder a substantial progress of successfully greened facades and thereby diminish their possibilities (image 13).
As long as very few and often dismal façade greenings fight against the gray of the city it keeps being difficult to convey the advantages and potential of facade greenery. Poorly executed facade greenings reveal their futility sooner or later (usually at the latest after 20 years) to everyone without any deep analysis. They simply are going to look shabby and become disadvantageous (in particular traditional façade greening with self-climbers) no matter if the reason for this is based on poor execution and/or neglected maintenance. In contrast to this, most of the time everyone can easily detect successful facade greenings, primary for the reason that they are considered as a beautification of the cityscape.
Instruments of a more or less direct funding (usually a matter of local politics) may not be forgotten when pursuing success in facade greenery. In some places there still exist funding programs which provide financial support for facade greenery. I can no longer see a sustainable benefit for that. In 1980 there were considerable subsidies for facade greenery in cologne. Several of those pushed measures are long gone and those remaining are mostly rundown. This kind of subsidy may have led to the realization of some additional projects of facade greenery. But it has not contributed to a sustainable success of façade greenery because the projects are no longer good-looking or free of faults.
In images 13 and 14 I depicted that even perfect facade greenings, which denotes optimized efficiency and minimizes maintenance and terminates the need for repairs, only become really beneficial with longevity. Whereas the one-time investment for its installation is quickly forgotten, there is possibly a need for a costly annual maintenance. In theory this increases the longevity and thereby the benefits of a project. In practice the required maintenance is often neglected because of the efforts. This approach is very shortsighted since a sufficient maintenance could compensate for ill-planned and badly executed facade greenings. In order to optimize the success of façade greenings, which is in the public interest, the focus should be shifted to subsidize maintenance in terms of organizational and practical help. Apart from that, I think it is only fair that benefiting societies cover parts of the costs of façade greenings, even if they are located in public space.
Details on the successful realization of durable façade greenings (traditional approach).
Despite all innovations and the increase in know-how in façade greenery there is still a lot of room for improvement of the actually perceivable success of this “old approach”. This is underlined by a vast number of examples which one can find virtually everywhere. Improvements in traditional façade greenery are a necessity. The new methods are an addition to the traditional approach – not a replacement!
After talking about general strategies for optimizing the success of facade greenings I now will present detailed perspectives of improvement possibilities concerning planning and execution. The already mentioned FLL guidelines, numerous literature and also the internet offer comprehensive information that help to enhance the success of greening projects. Therefore I will confine myself to presenting an overview.
According to the choice of climbing plants for the traditional approach of facade greening, different climbing strategies are applied. The decision for or against self-clinging plants is already a significant one (compare image 15) – for instance for the demand of climbing supports (or espaliers).
Traditional facade greening: Selection of plants
Not only climbing plants can be considered for useful vegetation of facades. Also greenings with espalier fruit and other espalier plants (for example ground-cover plants) are associated with traditional façade greening. When choosing espaliers in very close proximity to the exterior facade, there are some things that have to be considered: due to formation of roots with effects on statics we cannot put espalier greening on the same level as a greening utilizing climbing plants. Since espalier plants don’t climb actively, they don’t need a specifically suited climbing assistance. The esapliers serve primary to create a „unnatural“ growth habit and if necessary as pillar. The rather two-dimensional, above-ground appearance and the support needed for that is conducted by human intervention (tying down espaliers) and not by the plants themselves.
In traditional facade greening, the trellis-climbing plants increasingly gain importance. A majority of greened buildings in the last century showed the use of self-climbers (which was unproblematic). However, modern facades are often not suitable anymore for this kind of direct greening. Self-climbers involve the risk that there might be damage to all kinds of heat-insulating exterior facades which cannot be completely contained by constructional appliances and / or periodical pruning.The disadvantages of a direct greening – especially the undesired spreading and static load on the weather protection layer – can be reduced by using trellis-climbing plants with climbing supports. Some twiners and climbers develop vigorous growth, so that they can be used for greening tall buildings with an appropriate climbing aid.
Self-clingers can climb rough vertical areas more or less directly, whereas trellis-climbing plants require more filigree structures so that they can unfold their facade climbing technique. These structures, called “climbing supports” should suit the climbing strategy and climbing ability of the trellis-climbing species better than in nature, since facades are very difficult locations for all kind of plants due to the exposition of wind and intense sunlight. In nature, they gain height by climbing grasses, shrubs and trees, which provide stems, twigs and branches in great number, various dimensions and different directions. This natural environment can only be recreated to some extend for the purpose of facade greening. Basically, the possibilities are confined to installing area-covering climbing supports which provide shapes that can be covered by the plants fast and safely and support the direction of growth and the climbing strategy of the selected plant.Twiners predominantly vegetate climbing aids (which are vertically orientated) with round profiles that have large gaps to each other. For climbers, the profile section is almost irrelevant. But the perimeter is limited and the gaps (width of field) have to comply rather with the rigidity of the sprouts than with the growth of vegetation. For scramblers, (in nature, additional help for elevation is provided by the undergrowth) climbing aids are suitable only to a limited extend since they consist of “dead material”. In this case, acute-angled structures are advantageous, however most of the time a support for climbing has to be provided by tying up or insertion. Ground-cover plants and growth-restricted shrubs do not differ significantly compared to scramblers in this regard.
The previously mentioned remarks on the use of climbing plants show a connection between plant and facade (with or without climbing aid), this connection is highlighted by the word “facade greening” (or green facade). The dependencies of the connection of plant and facade require well thought out selections. But they are by far not the only parameters that have to be considered. Thus, facade greening on a big scale can only be successful when it was planned competently and thoroughly.
Aspects of planning – interaction of the components
The general perception (including the views of a lot of construction experts) is that traditional façade greenery is a very simple matter. As a manufacturer of climbing aids I predominantly receive “immature” price inquiries which cannot be worked on without the necessity to check back with the customer. I think this is an indication for the superficial planning of facade greening.
Planning and optimizing of facade greenery require interdisciplinary competence. Well planned facade greening is distinguished by selecting proper components, suiting the prerequisites perfectly. Looking at the implementation of climbing supports like illustrated in image 17 (for self-clinging and trellis-climbing plants), it has to be noted that the whole circle has to be taken into consideration and that the respective points have to be well-adapted to each other. In order to optimize benefit and success, the reduction of maintenance is a high priority.
Climbing plants – growth / static aspects
Apart from the already discussed climbing strategies and demands on the location (which can also be accessed in numerous specialist literature) a major consideration has to be given to the growth of different plant varieties and plant species (image 18). Just a single climbing plant can “overgrow” a façade. Growth does not simply stop because the intended area has been covered. Due to that, an increased maintenance (pruning) will be required and there is an increase of possible deficiencies and damage.
Optimal adaption of vegetation to the dimensions of the area that is intended to be greened is also advantageous in regard to appropriate sizing of climbing aids and their fastening to the building. Except for the weight of the wood of the different species, there is coherence between growth and deadweight (dry and wet) since the total area of the foliage is a major issue. The loads of wind and snow have to be estimated in regard to the growth of the vegetation because there will be large overhangs in the forward direction. Consequently the contact surface concerning wind increases parallel to the façade and at corners as well as the supporting surface for snow and ice.
Numerous vigorous growing climbing plants develop thicker main shoots which require greater distance from the climbing aid to the façade. Larger cantilever arm of fastenings means greater level length and consequently higher demands on the rigidity of fastenings and their anchorage to the supporting framework. Greater secondary diameter growth results almost inevitably in compressive stress or tensile stress. These incalculable additional loads affect climbing aids and fasteners. By maintenance or by regular rejuvenation these loads can be minimized. Since they can be responsible for deficiencies or damage it is even more important to construct appropriate climbing aids and apply a proper manner of fastening.
Facades – Exterior wall constructions
Regardless which climbing strategy is applied by the climbing plants or if they just require a strut, there will be a static (possibly dynamic) stress on components and ultimately on the supporting framework. Vegetation, respectively the system of climbing plant and climbing aid and the loads that apply has to be connected to the building in an appropriate manner. The solution of this task is determined by the present wall or facade construction (image 19).
Using self-clingers, the surface of the facade has to provide the necessary requirements (absence of cracks, joint-less, adhesion, load capacity). When using trellis climbing plants, there has to be a connection between climbing aid and supporting framework. This connection penetrates the surface layer and interlayers without impairing their function (weather protection and insulation). Composite heat insulation systems and curtain wall facades are the current most used facade constructions. Their fastenings require very large cantilever lengths. Considering composite heat insulation systems, attention has to be paid to the permanent impermeability of the penetration. The effort required for such fastenings is not only determined by the exterior wall construction but also by the plants that are chosen and also by the climbing aids’ construction and the manner of their fastening.
Climbing supports and manners of fastening
Climbing aids have to suit the needs of vegetation and climbing technique of the selected climbing plants and at the same time they have to be functional and appealing. In general, climbing aids, regardless whether they are shaped rather functional or rather playful, represent either a stand-alone or a subordinate design element based on features like shape, structure and color. However, German architects seldom use this design opportunity. Generally, they prefer “invisible” climbing aids. Thus in practice, there is a trend towards minimalistic solutions (image 20).
This minimalism approach to climbing aids results in favoritism of technical solutions for material and/or ways of mounting that do not always ideally suit the needs of the constructional preconditions or which neglect the impact of future growth. Every minimization brings along reduced costs but also limited applicability. The extreme type – single vertical profiles (ropes or rods)- is only sufficient for linear upward vegetation of twiners. But vegetation in horizontal direction can only be controlled to some extend and does hardly contribute to coverage of the facade. Minimizing of climbing aids may provide financial advantages in the short term, but also result in deficiencies, risk of damage and high-maintenance. Excessive minimizing of climbing aids may result in useless and maybe even harmful facade greenery. Minimizing of climbing aids does not only reduce their functional quality but also the possibility to ideally connect it with the building at little effort.
Generally, climbing aids can be constructed in a way to suit specific mountings (image 21) which depend on the construction of the facade and additional particular circumstances. By using different ways of mounting to allow initiation and/or ablating of loads where it is convenient, technical and financial aspects can be taken into account. This results in the use of plenty inexpensive mounting elements on a surface area or just a few on selected spots, if the place is less convenient.
The bigger the distance between supporting framework and climbing aid due to facade construction, the more difficult and more complex is the implementation of climbing aids. Also the solidity of the facade has to be considered (the less solid the more difficult). In such cases it is recommended to use climbing supports which construction enables redistribution and even ablation of loads. In theory, a lot of climbing aids could stand on their own foundation, regardless of the facade and consequently not requiring any mounting to the facade. However this is not achievable with ropes or nets and should generally be carefully considered due to cost concerns. However, an ajar climbing aid can be very reasonable because its fastening to the facade often just has to withstand wind pressure and wind suction. Disadvantageous preconditions on site do not hinder to implement an easy and slim mounting in spite of the high load capacity of the climbing aid. In practice this opportunity is still seldom used.The use of optimized facade mountings of more functional climbing aids would enhance the success of traditional facade greenery in practice significantly.
Climbing supports and fastenings, assembling and maintenance of the plants (especially the necessary prunings) are the most costly components of traditional facade greening. Hence, an optimization is very effective, wherever the object of greening demands the use of big and heavy climbing plants. Since these are high maintenance due to increased growth, and maintenance has to take place in great height, every investment that reduces the need for pruning pays off.
General views on traditional facade greening and „vertical gardens“ in regard to successful realisation
In spite of my efforts to present a comprehensible structure, my comments on traditional facade greening may appear somewhat chaotic. Sometimes I arrange according to plants, sometimes according to facades, climbing supports, methods of mountings, etc. And as soon as I prioritize a different component, new conditions seem to apply.
But facade greening is not chaotic, it is „just“ complex. Actually, all the dependencies (see figure 17, „planing circle“) could be put in formulas with functions „if, then, else, and, or“. Considering the variety what facade greening should or could accomplish in different cases and considering numerous methods of implementation under almost endless different preconditions makes it impossible to create such a „universal formula“ for determining the best implementation possible.
And as long as many projects are being compromised due to a few euros (€) per square meter the costly efforts being put in such a formula would not be well spent.
New developments („Living walls“ etc.) contribute to the potential variety of facade greenings. (see image 22)
Although the audience is excited for existing examples (especially the art of Patrick Blanc), there is still a lot of doubt, particularly due to costs. This is nothing new. In fact, everyone who advocates facade greening for a long period of time will encounter endless discussions about costs being too high.
The future will show, if new methods and systems, which are to date significantly more expensive than traditional approaches to facade greening, can establish. Evidently, they are often considered as reasonably priced in other countries. If the new methods succeed in realizing new dimensions of useful facade greenery then chances are quite good for numerous successful projects in Germany.
It will take a while, until really reliable solutions are found for difficult conditions (climate, height). When considering this aspect, there are still advantages for the traditional approach to facade greening: well-engineered methods and sufficient know-how are steadily available.
In general, specialists are equipped with in-depth knowledge and experience, also in regard to dependencies of location and exposition, facade construction, facade vegetation and techniques, so that adopting several components for living walls and vertical gardens should not be a problem, just challenging at most.
The success of future greening projects -regardless of which method is used- is rather based on creative and proper implementation to challenging facades and other objects. In order to maximize the success, greenings must deliver reliability and long-lasting functionality combined with appealing design.
I hope that my remarks today will contribute to that.