The RIC Good Wood Guide


(See also Biotecture II: Plant­Building Interaction and Pleaching)



by Rudolf Doernach

The following is adapted from an article titled On the Use of Biotectural Systems published in Permaculture Journal No. 7. It is based on a lecture given by Rudolph Doernach to landscape architects in Bonn, Germany. Doernach's work goes far beyond the points canvassed below of creating an oxygenated, disease-free environment, and 'bio-fitting' described here; it also encompasses the growing of whole houses on land and beneath the sea!. (See also the comments on Biotecture and Turf Roofs in Non Timber Building Materials)

The diseases of civilisation have primary, secondary and tertiary causes. It is very probable that the primary cause of cancer is shortage of oxygen. When oxygen is deficient, all the secondary and tertiary disease factors greatly increase in their importance.

Thus, in order to effectively combat cancer, but also diseases of the circulatory system, rheumatism and schizophrenia, plants and the oxygen they produce must be brought into our towns, homes, factories and offices. This article attempts to demonstrate how this can be done, with considerable economic benefits, and at almost no cost, as no large scale research is called for. Although the approximate calculations are only rough estimates, they nevertheless give an idea of the scale of the problem by attempting to draw up an overall balance sheet.

A shocking balance and an alternative calculation

1. Oxygen deficits in major European cities: Stuttgart up to 50% deficient; Vienna up 75%; Paris up to 85%; New York up to 90%.

2. Cancer sufferers in the German Federal Republic: approx. 30% of the population.

3. Sufferers of diseases of the circulatory system in the GFR: approx. 50% of the population.

4. Mentally ill people in the GFR: approx. 8% of the population.

5. Sufferers from excessive noise levels in the GFR: approx. 30% of the population.

6. Consumption of land in the GFR: approx. 125 hectares per day.

From this scenario it can be seen that no health system, no matter how well off, can afford the resulting health costs in the long term. An attack at the roots of the problem is is thus long overdue. How much would this cost in comparison to health service costs?

a) Health service costs

The GFR has a population of approximately 60 million. About a quarter of them, say 15 million, pay 2 ,000 Deutschmarks each in annual health service dues, making a combined total of DM 30 thousand million.

b) The alternative calculation

The same country has about 10 million homes with an average area of about 50 square metres. This is equivalent to a total built area of approximately 500 million square metres. Industry, administration and schools etc account for about the same area again. Total: approx. 1 thousand million square metres or 100,000 hectares.

Taking into consideration the fact that some of these are multi-storey buildings or are terraced, and allowing for window openings, these 100,000 hectares of usable floor space have at least 50,000 hectares of plantable external surface.

If only half of these vertical facades were planted over the next ten years, then approximately 2,500 hectares would have to be tackled every year. The planning, planting and maintenance of this, including the trellis work would cost about DM 50 per square metre ­ roughly the same amount as for upkeep with conventional materials. On this basis, the annual turnover would be about DM 1 thousand million. It would provide approximately 25,000 jobs for planners, 'biotects' and gardeners, etc, and would amount to only about 3% of the necessary annual health service costs.

But now to the potential effects of 250 million square metres of planted building surface in our cities.

1. Oxygen production: An annual oxygen production figure of 0.5 kilograms per planted square metre would correspond to a total annual production of about 125 million kg.

The estimated value in health terms: approx. DM 125 million per year.

2. Conversion of carbon dioxide: Approximately 1 kg per square metre per year.

Estimated value in health terms: approx. DM 500 million per year.

3. Noise reduction: By their movement, large-leaf evergreens dissipate airborne noise, especially at the critical high frequencies, the reduction of which has a double effect. The monetary value of this is estimated at not less than DM 1 thousand million per annum.

4. Reduction of dust and germs: Plants cause the deposition of dust particles together with airborne viruses and are thereby up to 90% effective in cleaning the air. Inorganic materials are not able to remove viruses in this manner. The economic benefit based on the saving of work-days otherwise lost through illness and increased productivity is estimated at a minimum of DM 5 thousand million per annum.

5. Energy: The covering of facades with a carpet of vegetation cools in summer and insulates in winter. In summer, the resident of a green street is more active, less water is used, and the temperature can be lowered by as much as 5° C. In winter, the loss of energy from buildings can be reduced by as much as 30%. Economic assessment: 10 million homes with an average annual heating bill of approximately DM 1,000 results in a total annual heating bill of about DM 10 thousand million. If facade vegetation saves only 5% of energy costs per annum, then the saving would amount to some DM 500 million per annum.

6. Psychological effects: Living plants refresh the spirit and generate joie de vivre... The absence of green causes depression, and results in stress and mental illness... If only one person in a hundred suffers from mental illness, this nevertheless amounts to a total of about 0.5 million patients, generating annual costs of at least DM 10,000 per annum. The saving in social service expenditure would amount to about a further DM 5 thousand million per annum.

On the basis of these estimates, the overall benefit of 50% application of vertical green systems in the German Federal Republic would be of the order of DM 10 thousand million per annum. This has to be set against an annual investment of only about DM 1 thousand million per year over a period of about 10 years.

On the basis of this calculation, such green systems would pay for themselves tenfold, in other words they would have an economic return which industrial products or export goods can hardly expect to compete with. What is more, this calculation does not include the full costs arising from such diseases as cancer or circulatory problems, nor does it take into account the effect that 250 million square metres of plant surface has on the improvement of water quality. Other benefits include the production of biomass (compost, fruit, etc) as well as such positive side-effects as environmental improvement, prevention of the migration of people from the cities, etc.

How does insulation function in a living building?

The significant advances have come as a result of the consieration of the leaf as a living solar collector (probably the best that there will ever be). This 'vegetative' solar collector orientates itself optimally to correspond with the diurnal and annual path of the sun, and has the following effect:

  • In summer, the evergreen leaf is raised in correspondence with the high angle of the sun, thereby operating as a 'ventilation blind'. Thus it cools by means of a chimney effect between the plant and the building. This is supported by the transpiration from the plant. This results not only in the air conditioning of individual buildings, but even in the generation of 'urban breezes'. (In many poorly ventilated cities, the use of vertical vegetation systems will allow the initial introduction of local winds).
  • In winter, the leaf of the evergreen lowers its inclination on account of its low hydrostatic pressure, in accordance with the low angle of the sun. Together the overlapping leaves form an insulating layer of stationary air around the building which is the reason for their energy-saving effect.
  • In hot countries such as Australia or Brazil, it is the cooling effect of the plant layer which is interesting, while in Germany and the rest of Europe, research into the (active) production of energy and the (passive) thermal insulation properties of the plant layer takes precedence.

    The following factors are important in the active production of warmth:

    1. The homeostatic (respiratory) warmth resulting from cellular respiration, although in winter this is at its lowest.

    2. The removal of heat from the composted biomass of deciduous systems.

    3. The production of frictional heat as a result of wind action.

    At present, the so-called 'Bioklin' which extracts the warmth from composted leaf biomass and delivers it into the building lies at the centre of interest. In passive thermal insulation, the following factors are important:

    1. The aerodynamic, physiological and morphological characteristics of a species or a combination of species. These include leaf colour (reflection and absorption coefficients), leaf size, leaf orientation (overlapping), leaf weight, leaft density, aerodynamic characteristics of the leaf, the system and the attachment of the climber, and the stability of the overall system.
    2. Especially surprising results were obtained in investigations into separated and integrated combinations of deciduous and evergreen species. By means of so-called mixed plantings (also know as poly- or matrix planting) in which various species were combined in a multilayered fashion, one family shading and sheltering the others (evergreens, requring less light are thereby located in the under-storey), energy savings of up to 35% were achieved.

    In order to confirm these astonishingly good results, the measurements must be repeated, however those who are aware of the results of other researchers into the productivity of mixed cultures will not be suprised by such claims.

    Climber trellises, climber systems

    It seems that climbing plants growing directly in the earth as combinations of deciduous and evergreen species offer the most promising results. The plants can either cling directly to the wall of the building or can be kept at a distance from it by means of a supporting structure. In many cases (and this can be demonstrated for between 60 and 70 years) growth directly on the wall has protected the rendering rather than damaged it. (In those cases, reported unplanted walls of houses in similar locations needed to be newly rendered or repaired 3 or 4 times during the same period.) Nevertheless there are cases, especially on exposed north and west walls, where direct growth has damaged rendering, thereby allowing the entry of water and leading to frost damage. For this reason, direct growth of evergreens on west walls is not recommended.

    In order to improve the overall performance of vegetation layers, a light supporting structure is therefore recommended on all walls; for example:

  • A 50 x 50 cm lattice of stained timber mounted on wooden posts, dimensioned to withstand surface winds, and stretching from roof to ground. Small hardwood separating blocks should be built in between the wooden elements to ensure drying out takes place.
  • Alternatively:

  • Coloured polypropylene ropes anchored in the ground and stretching to the roof, with supplementary horizontal ropes or netting as required by the height of the building or the species of climber. Adjustable tensioners are necessary in order to minimise wind noise. (Concern with infestation by ants and other insects associated with climbing plants is usually needless, as a balance is maintained by the fact that there are many nesting opportunities provided.)
  • For buildings in cold localities, the folowing measures are recommended as providing optimum results:

    1. South face: Deciduous, fruiting species growing away from the surface of the wall to produce a cooling chimney-effect in the summer. In winter, the shallow rays of the sun are not reflected by foliage and will therefore warm the wall behind it; this wall should consequently be dark in colour.

    2. West wall: In the presence of a lot of westerly sunshine, and where driving rain from the west is insignificant, the west wall can be treated in the same way as the south wall. Otherwise, evergreen species set away from the wall, forming complete cover without any cooling effect, but retaining a warm cushion of stationary air.

    3. East wall: If the wall receives the full force of the morning sun, it should be treated as for the south wall, otherwise as for the west wall ­ ie, with evergreens.

    4. North wall: Fully covered with evergreens as an insulating carpet of vegetation, protecting a stationary cushion of air. Further refinements can also contribute to efficiency; for example, systems which have heat barriers, systems which collect biomass and create nesting places, or even systems with rear/internal reflex layers which result in a denser growth.

    Today's industrial society is developing from technology through automated micro-technology towards bio-technology. A similar trend should be aimed for in the construction sector. However, the biologically productive versions of facade treatment will have to establish themselves in the face of competion from the producers of biologically inert, high energy-dependent building materials.

    In summer, the evergreen leaf is raised to correspond with the high angle of the sun, allowing cooling air to enter between plants and building.

    In winter, leaves are lowered in accordance with the low sun angle, creating an insulating sheath of stationary air around the building.

    Moisture to be kept away from the building as far as possible; thus no evaporative cooling in winter.

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