Wood pest control

from Wikipedia, the free encyclopedia

Wood pest for construction and plant timber is used compared to preventive wood preservatives combat activity on wooden acting animal and fungal timber pests . The control of wood pests in the forest sector is a separate topic.

Legal / normative regulations

The control of fungal and animal wood pests is essentially regulated in Germany in DIN 68800-4. In contrast to parts 2 and 3 of the standard, which deal with preventive wood protection measures, part 4 has not been introduced by the building authorities and therefore has no legal force. The recommendations of this part of the standard are, however, recognized rules of technology and are, as a rule, a prerequisite for a professional control measure. In justified individual cases (for example in the area of listed buildings) it can make sense to use a special procedure that deviates from the standard.

For certain types of pests, especially dry rot , longhorn beetles or termites, there is a reporting obligation anchored in the respective state building regulations in some federal states .

In connection with wood pest control measures , other legal regulations are often affected, for example the Chemicals Act and the Hazardous Substances Ordinance .

Process engineering

The wood pest control methods currently approved in Germany can be divided into the following categories:

Chemical wood pest control

Here, using chemical wood preservatives approved according to the wood preservative directory, fungal and animal wood pests are combated. The chemical control of wood-destroying insects can be roughly divided into two areas.

  • Chemical control by treating the wood surface
  • Chemical control through borehole injections

A standardized control of fungal pests in wood is fundamentally not possible with chemical agents. Wood preservatives against fungi can only be used preventively in wood. The only standard-compliant measure to combat fungi in wood is currently the dismantling or cutting back of the infected wooden parts (exceptions are possible for building components that are valuable as a monument). In the event of an infestation by wood-destroying fungi in the masonry (especially by the real dry rot ), on the other hand, chemical agents (so-called “sponge barrier agents”) are used to contain the infestation.

Hot air process

Animal wood pests are killed by heating infected wooden components. The control in the hot air process is essentially carried out in two application techniques:

  • on the wooden components or the overall wooden structure of a building with mobile equipment.
  • in mostly stationary humidity-controlled climatic chambers with closed air circuits . The use is aimed at transportable wooden components. Thanks to the precise control of temperature and humidity, this technology can also handle very sensitive parts.
  • small objects such as watch cases can be sufficiently heated in a sauna. Metal parts should be removed beforehand.

Mobile combat on buildings

Basic features of process engineering: Large amounts of hot air (~ 12,000 m³ / h at 120 ° C) are blown into the roof structure with high-performance air heaters. By continuously flowing hot air around all exposed construction timber, they are slowly heated.

At a temperature of 55 ° C inside the wood, the larvae and eggs inside begin to be killed. Due to the high time tolerance, the killing has taken place after 60 minutes. The mode of action of the thermal processes is that the insects located in it are killed by protein coagulation in all stages (eggs, larvae, pupae, beetles) through sufficiently high temperatures in the entire cross-section of the wood. The destruction is controlled by regularly checking the air and wood core temperatures with measuring sensors. With appropriate planning and special technology, the heating can also be used in areas that are difficult to access or shielded (for example, sloping ceilings, shelves, ceiling cavities or the like). Experience has shown that the heating time for an average roof structure is around 6 to 14 hours.

With this method, 100 percent immediate killing of all wood pests can be achieved in the heated wood without the introduction of chemical agents. The success of the measure depends on conscientious planning, professional craftsmanship and the associated quality assurance measures. Only specialist companies with appropriate expertise (e.g. certificate of expertise for wood preservation in construction) who have the relevant knowledge, verifiable experience and the necessary technology (see respective state building regulations, DIN 68800-4 and VOB ) are to be entrusted with the control measures .

The thermal processes do not offer any preventive protection against new infestation by wood-destroying insects.

Impermeability: The room to be treated does not have to be completely impermeable, as hot air is constantly supplied, which then has to make room for the hot air flowing in. However, uncontrolled escape of the supplied hot air through larger openings such as windows, door openings, etc. does not make sense. Rather, the air should escape specifically at the lowest points in the room (e.g. eaves of the roof).

Temperatures: The object requires special testing with regard to heat tolerance. The air temperature in the room to be treated should not exceed 120 ° C in the long term. The outlet opening of the supply pipe must be kept at least one meter away from easily inflammable materials (building material class B3 according to DIN 4102-1; paper, cardboard and the like). If there are heat-sensitive components (plastics, electronic components, etc.) within the rooms to be heated, suitable precautions must be taken.

Stationary systems

The stationary systems use the same application principle. Correspondingly constructed chambers are used for treatment, in which mainly transportable parts are treated. In a closed circuit, the air is electronically controlled and appropriately tempered and humidified.

Microwave overheating

A magnetron with an attached horn radiator shines through the wood and overheats all (water-containing) living beings within about three minutes. The prerequisite is a sufficiently strong electromagnetic field, which is why the irradiated volume with a 500 W magnetron should not exceed 10 liters. By packing the target volume with a metal foil, the field strength can be increased and the duration reduced. The method has proven itself particularly with roof beams, but it does not offer any preventive protection against new infestation by wood-destroying insects. When using a magnetron, however, it must be taken into account that all water-containing parts are captured by the microwave radiation, including the water molecules that are present as residual moisture in the wood fibers. Too high an energy supply can therefore lead to charring or burning of the wood. If the energy supply is too fast and if it is closed accordingly, this may also lead to the formation of cracks in the wood.

Fumigation

There are two groups of gases that are used:

  • Gases whose use, due to their high toxicity, requires proof of special skills on the part of the user.
  • Gases that have a predominantly asphyxiating effect and are not subject to any restrictions on use.

By fumigating infected wood, animal wood pests are killed in buildings or in chambers (e.g. container fumigation ).

See also

literature

  • German Institute for Building Technology (DIBt) (Hrsg.): Directory of wood preservatives. List of wood preservatives with general building authority approval - List of wood preservatives with RAL quality mark - List of blue stain protection agents in accordance with VDL guidelines. 55th edition. 2007, 271 pages, 14.4 × 21 cm, paperback, Erich Schmidt Verlag Berlin, ISBN 978-3-503-10029-3 .
  • Johann Müller: Wood protection in building construction. Fraunhofer IRB Verlag, Stuttgart 2005, ISBN 3-8167-6647-1 .
  • WTA ( Scientific-Technical Working Group for Building Preservation and Monument Preservation ), (Ed.): Merkblatt 1-1-08 / D Hot air methods for combating animal wood destroyers IRB Verlag 2008.
  • WTA (Scientific-Technical Working Group for Building Preservation and Monument Preservation), (Ed.): Merkblatt 1-2-05 / D Der Echte Hausschwamm IRB Verlag, 2005.
  • DIN , (Ed.): DIN 68800–4: 2012-02 - Wood protection - Part 4: Control and remedial measures against wood-destroying fungi and insects.
  • Dietger Grosser: Plant and animal construction and timber pests. DRW-Verlag, Leinfelden-Echterdingen 1985, ISBN 3-87181-312-5 .
  • Hans Peter Sutter: Recognizing and combating wood pests on cultural assets. Paul Haupt Verlag, Bern Stuttgart Vienna 2002, ISBN 3-258-06443-1 .
  • G. Becker: Studies on the nutritional physiology of the longhorn beetle larvae. In: Journal of Comparative Physiology . 29/3, 1942, pp. 315-388.
  • W. Behrenz, G. Technau: Investigations on the immunization of wood by hot air treatment . In: Wood as a raw material. (European Journal of Wood and Wood Products), Volume 14, Issue 12, 1956, pp. 457-458. doi: 10.1007 / BF02605506
  • DIN, DGfH (Ed.): Wood protection. Structurally - chemically - fighting. Explanations to DIN 68800 part 2, -3, -4. Beuth Verlag, Berlin 1998, ISBN 3-410-13959-1 .
  • David Pinniger, Bill Landsberger, Pascal Querner, Adrian Meyer: Handbook Integrated Pest Management in Museums, Archives and Historic Buildings. Gebr. Mann Verlag, Berlin 2016, ISBN 978-3-7861-2760-4 .
  • Uwe Wild: Lexicon of wood protection. BAULINO Verlag, Waldshut 2009, ISBN 978-3-938537-07-7 .

Web links

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