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Evaluation of exposure conditions for wooden facades and decking
2009 - IRG/WP 09-20408
During their functional life, building components are exposed to moisture and other environment stress conditions in numerous ways. This is a fact that should be taken into account during manufacture, product development, designing and work execution of building components. For wood material, moisture stress and biological factors like mould and decay fungi are often critical in cladding and decking structure in exterior use conditions. For mould and decay development, different mathematical modelling exists based on laboratory and field studies. These can be used also for evaluating the different material properties for durability and service life of wooden products. In the future, the life time expectations and analyses of different building products will need more data on the durability of products, service life and resistance against mould and decay, not only data on wood material itself. The mould and decay models can be incorporated with climatic and building physic models to evaluate the effect of different exposure conditions on the durability and service life of wooden products.
H Viitanen, T Toratti, R Peuhkuri, T Ojanen, L Makkonen


Modelling of onset of mould growth for wood exposed to varying climate conditions
2009 - IRG/WP 09-20414
A performance-based service life design format based on climatic exposure on one hand and “resistance” of wood against mould growth on the other hand, is presented in this paper. A limit state for onset of mould growth is defined as the occurrence of traces of mould observed by microscopy. A dose-response model is proposed by which onset of mould growth can be predicted for an arbitrary climate history of combined relative humidity φ and temperature T. The model is calibrated and verified against a comprehensive set of experimental data published by Viitanen (1996) describing mould development on spruce and pine sapwood as a function of climatic exposure. The model is applied to predict time to onset of mould growth under natural outdoor climate (under shelter) as well as mould development in building attics and in crawl space foundations. The predicted response shows reasonable agreement with experimental observations and proven experience, although biological processes of this type display great variability. The results indicate clearly that a generally applicable, quantitative model can be used as a powerful tool for moisture design in practice. The model is designed to facilitate continuous improvement of prediction capability by further laboratory testing of various materials under specified climate conditions. It is concluded that the model in combination with currently available building physics software is suitable for moisture safe design of wood-based components in the building envelope. A further step should be to develop methods to manage uncertainties by introducing reliability and risk concepts into the service life design process.
S Thelandersson, T Isaksson, A Ekstrand-Tobin, P Johansson


Onset of mould growth – the effect of climate variability and different geographic locations
2010 - IRG/WP 10-20446
This paper presents a study on how climate conditions at numerous locations in Sweden affect the risk of onset of mould on wood sheltered outdoors. The results indicate that the risk is clearly higher in the south compared to the north of Sweden. These differences are mainly explained by colder and dryer winter periods in the north which is unfavorable for development of mould. The results also show that the climate effect with respect to risk for mould growth has a significant variation between different years. Thus, the risk for unfavorable effects cannot be solely based on predictions for a so-called normal year without considering years with more extreme climate effects. Based on the results it is argued in favor of developing a quantitative method to assess the risk of mould growth using probabilistic methods and reliability analysis. Such a method should be simple enough for the general engineer to implement and serve as a valuable tool in order to avoid inappropriate design and potential health related problems.
M Häglund, T Isaksson, S Thelandersson


On the effect of climate and exposure conditions on durability indicators and their potential for service life prediction of wood-based products
2016 - IRG/WP 16-20576
In order to encourage increased use of wood, different user groups need to be better informed regarding the variation in performance between different wood materials and the effect of different use classes. It is also important to provide good empirical data on the service life of wood products as input to for example life cycle assessment studies. In the current study the effect of temperature and moisture on the performance of different wood materials in laboratory decay trials was evaluated by different approaches and compared with field exposure data. The same materials were used throughout the different tests in order to reduce variation. The durability class allocation varied, as expected, between test fungi, climates, exposure times, and decay tests. This confirms that the durability classification of a material, and the ranking between materials, is not a fixed value that can be based on one single test. Interestingly, for the most durable materials and for Scots pine sapwood (low durability) the variation in durability classification seemed to be somewhat lower than for the materials with intermediate durability. A regression model approach was used in order to predict field performance from laboratory data. However, this approach was not successful and confirms that more sophisticated models are needed in order to make good predictions of service life.
G Alfredsen, C Brischke, P-O Flæte, M Humar, L Meyer-Veltrup


Low temperature drying conditions of Pinus radiata wood for avoiding internal stain
1989 - IRG/WP 3507
It has been observed that, if in little sawmills, timber is dried with a low temperature schedule, it arrives at destination with internal sapstain besides of superficial mould. In this study, the lowest drying temperature at which wood should be exposed for sterilization, which results to be 52°C, is searched. It is not possible to avoid entrainment of pentachlorophenol, even though a waiting period of 72 hours after dipping the wood in a pentachlorophenate/borax solution before drying is considered. The residual content of pentachlorophenol in wood should be at least 400 µg/cm² or the moisture content less than 23% for avoiding the development of mould.
M C Rose


A proposal for an international wood preservation standard
1994 - IRG/WP 94-20031
Two factors are driving the need for an international wood preservation standard. First, the global need to use our natural resources more wisely and second, the movement towards free trade exemplified by the General Agreement on Tariffs and Trade. The International Research Group on Wood Preservation is the ideal organisation to undertake the task of developing such a standard. This paper is intended to start this process. It attempts to bring together the best points of a number of national and international standards into a uniform format. Preservative penetrations and retentions for each commodity would be based on the hazard class/use category, the climate zone, the biological area, the natural durability of the heartwood of the species used, the service life required and the consequences of failure. The outline standard presented borrows heavily from the new European Standard and is presented as a possible starting point for the development of an international standard.
P I Morris


Effect of protective additives on leachability and efficacy of borate treated wood
2002 - IRG/WP 02-30290
Borate preservatives have been used extensively in many countries as an effective means for protecting wood against fungal and insect attack especially in interior environments. Under exterior conditions, borate compounds have a main disadvantage as they can be leached from treated wood as a result of their water solubility. In this study, we compared the potential of different additives for reducing the leachability of boron preservatives from treated wood. Scots pine sapwood (Pinus sylvestris) and poplar (Populus trichocarpa x deltoides) test samples were vacuum treated with 1 % BAE (Boric Acid Equivalent) disodium octaborate tetrahydrate (DOT) solutions containing various additives e.g. glycerol/glyoxal, polyvinylpyrrolidone (PVPY), a commercial resin compound and a commercial water repellent. The European Standard EN 84 was used as a leaching test for both coated and uncoated specimens. The results of chemical analysis of leachates taken at different periods showed that the use of protective additives reduces the boron leachability. The glycerol/glyoxal additive applied to treated pine sapwood showed the best performance. The percent of boron retained in uncoated pine sapwood was 26% while coated samples still retained 45% after 14 days of intense leaching. Similar tests on poplar revealed 19% and 34% for uncoated and coated samples, respectively.This represents a gain of 20 to 25% compared to pure DOT treated specimens of both wood species. Preliminary biological tests were carried out on malt agar using a miniblock technique for uncoated pine sapwood and beech, with Poria placenta and Coriolus versicolor, respectively. After six weeks of exposure to fungal attack all boron protective systems tested proved their effectiveness, as none of the test samples exhibited a mass loss exceeding 4%. The reference 1% BAE without protective additives showed an average mass loss of 15%. Finally, test data are reported of standard EN 113 testing in view of a further evaluation of the biological efficacy of combined DOT-additive treatments.
A Mohareb, J Van Acker, M Stevens


An attempt to evaluate wood resistance against fungal decay in non-sterile conditions by measuring the variation of resistance to bending test
1988 - IRG/WP 2308
The main object of this work was to determine the variation of strength on large test specimens of wood (800 x 45 x 45 mm³) when exposed to accelerated fungal attacks close to natural conditions, out of test vessels. The modulus of elasticity (MOE) and the modulus of rupture (MOR) have been assessed. Thereby, the natural resistance of the wood species to fungal decay, the efficiency of preservative as well as the treatment applied are discussed. The wood tested is a guianese secondary species (Couma guianensis). The fungi tested are two guianese strains of brown and white rot. The exposure time is 12 weeks. No mould contamination has been recorded by use of a selective fungicide. The results obtained show that it is possible to infest in nonsterile conditions large wood specimens. Furthermore, modulus of rupture appears to be the most reliable criterion. The investigation, that requires limited equipment and staff could be performed in any tropical research station as it has been done at CTFT, French Guiana center.
L N Trong


Rules and conditions of the Ron Cockcroft Award Scheme RCA
1994 - IRG/WP 94-60025
IRG Secretariat


Conditions of the Ron Cockcroft Award scheme
1997 - IRG/WP 97-60086
IRG Secretariat


Conditions of the Ron Cockcroft Award scheme (RCA)
2003 - IRG/WP 03-60177
IRG Secretariat


Conditions for membership of IRG
1994 - IRG/WP 94-60024
IRG Secretariat


Conditions for membership of IRG
2003 - IRG/WP 03-60176
IRG Secretariat


Observations on the failure of anti-sapstain treated timber under non-drying conditions
1990 - IRG/WP 1437
A range of bacteria and yeasts were isolated from antisapstain treated timber and fresh sawdust. Solution samples containing 100 ppm of TCMTB in a nutrient medium were inoculated with these organisms and incubated at 25°C for 5 days. The levels of TCMTB remaining in solution were determined by HPLC analysis after this time. Results indicated high losses of active ingredient for a range of organisms. These results suggest that active biodetoxification of organic biocides could occur in a short period of time during storage of antisapstain treated timber under favourable conditions. The implications of these results are discussed.
G R Williams


Moulds and indoor climate in Denmark
2003 - IRG/WP 03-10488
Just like in many other countries after the oil crisis in 1972 Danish houses were tightened with the result that the relative air humidity rose considerably. The Ministry of Energy also demanded a lowering of the indoor temperature from 25°C to 20°C with the result that the relative air humidity rose even more. According to the latest survey 10% of Danish buildings are infected with moulds. Moulds occur in the indoor environment e.g. when humid air condensates on cold outer walls or in connection with water damage which is insufficiently dried out. In our analyses we always try to determine moulds both to genus and species. During our surveys in August 2001 and February 2002 we found 50 different species of moulds in Danish houses. The species Penicillium chrysogenum was dominating in both spring and autumn. Aspergillus versicolor was also present in spring and autumn but in smaller numbers. Cladosporium herbarum was most common during autumn. Stachybotrys chartarum was rather rare, maybe because it is closely connected to gypsum boards. It is very important to identify the moulds to species which is shown by the following case study. In a house where the sewer had been punctured in connection with establishment of district heating, 150 cubic metres of water had poured into the crawl space. We were called in by the occupant because she felt ill and there was a strong mouldy smell. We immediately asked her to move, with the result that her health improved almost instantly. She was so sensible that even the delivery of mail in her mailbox made her ill. A blood-test showed that she was sensitised to Trichoderma viride and Penicillium chrysogenum. The latter was found in large amounts in her house. We know that it is now possible to repair the house so that non-sensitised persons will be able to live there, but not the former occupant who will react to even small traces of allergen which are still there. After the repair we have different methods of quality control. It is now evident that some remedies and methods will kill the spores others the mycelium and yet others both. Some methods have a lasting effect, others do not. Our methods of quality control are either contact-samples with Petri dishes where mould colonies are counted and identified to species or a test for ATP or the Mycometer-test where the enzyme β-N-acetylhexosaminidase specific to fungi is measured. The Petri dish method measures the number of living spores, while the two other methods measure the amount of mycelium. However it seems that ATP in the mycelium is broken down faster than the enzyme measured by the Mycometer-test. Therefore it becomes difficult to decide whether the mycelium is living, partly dead or completely dead, when the repair work is going to be approved.
J Bech-Andersen, S A Elborne


Accelerated wood decay in a soil bed test under greenhouse conditions compared with a stake test under field condition
1991 - IRG/WP 2384
The rate of decay of oak, beech, Douglas fir, pine and spruce stakes in an outside test field were compared with the decay rate of the same species in a greenhouse soil-bed test. Strength loss after four and six months respectively was measured by determining the compression strength parallel to the grain. The results show that all species, strength loss in the greenhouse was 2 to 4 times higher than under field conditions. The rate of strength loss correlates with the rate of weight loss.
J E Polman, S G Michon, H Militz


Conditions for membership of IRG
2007 - IRG/WP 07-60246
IRG Secretariat


Conditions and possibility of nanobiocides formulation for wood protection
2008 - IRG/WP 08-30467
During development of nanobiocides for wood protection the need to identify mineral composition of wood in respect of trace elements and nourishing conditions of wood destroying fungi in relation to these elements was discussed.
J Wazny, A Kundzewicz


Conditions for membership of IRGWP
2012 - IRG/WP 12-60338
IRG Secretariat


Conditions for membership of IRGWP
2017 - IRG/WP 17-60411
IRG Secretariat


Effects of timber surface properties and dipping conditions on uptake of antisapstain actives from two aqueous suspensions, and ultimate effects on efficacy against mould and staining organisms
1995 - IRG/WP 95-30073
Green-off-saw rough sawn Pinus elliottii (slash pine) boards were dipped in aqueous suspensions of two antisapstain formulations, and the resultant surface retentions of active ingredients MTC (methylene bisthiocyanate), CTL (chlorothalonil) or TCMTB (2(thiocyanomethylthio)benzothiazole) were monitored by chemical analysis. Surface retentions increased with suspension concentration and surface roughness, and decreased with initial timber moisture content. Dipping time beyond 20 seconds, timber basic density and earlywood content had little effect. Relatively low surface retentions, produced by dipping smoother boards with higher initial moisture contents, provided lower protection against mould and stain during seasoning than higher retentions. Equations describing the effect of surface retention on efficacy were developed for both formulations, and retentions providing complete protection under the conditions of the test were determined.
M J Kennedy, T L Woods


Conditions for basidiospore production in the brown rot fungus Gloeophyllum separium in axenic culture
1984 - IRG/WP 1232
Attempts to control and optimize the production of hymenial structures and basidiospore production in Gloeophyllum sepiarium in axenic culture resulted in the proposal of the following conditions as being suitable. The dikaryotic mycelia originally isolated from basidiocarps could consistently be induced to produce hymenial structures and pure basidiospore collects if illuminated by near ultraviolet light with emission maximum at 355 nm ("black light") at a temperature of 15°C on a chemically defined medium, where the concentration of the carbon and the nitrogen sources were shown to be of critical significance. The necessary conditions for basidiospore production in lignicolous fungi in general are is briefly discussed.
J Bjurman


The rate of redistribution and loss of leachable preservatives under service conditions
1993 - IRG/WP 93-30026
This paper describes experiments carried out to determine patterns of preservative redistribution and any associated losses which occur when wood containing unfixed water-soluble wood preservatives is exposed to service conditions where leaching is possible. Scots pine sapwood treated with disodium octaborate was used as a model system. Results are recorded and discussed for trials representing painted joinery out of ground contact and unpainted stakes half buried in the ground. The results indicate that in the painted samples out of ground contact the water-soluble compound was redistributed longitudinally and away from the joint zone during the first months of exposure, although little redistribution occurred laterally. No difference in redistribution patterns could be associated with paint type. Ground contact stakes showed a loss in the water-soluble compound of about 40% in the first six months exposure. Most of this appeared to occur from the surface zones of the stake exposed to the weather, particularly from the extreme top. In addition, the compound appeared to migrate upwards from the below-ground portion of the stake to the above-ground portion. These results provide new information on the extent of movement of water-soluble preservatives in painted, jointed timber out of ground contact and in unpainted timber in ground contact. It is concluded that the long-term significance of the observed redistribution effects for painted joinery should be evaluated to confirm that there is no likelihood of shortcomings in performance in practice. For the ground contact situation, results confirm that rates of redistribution and loss are high enough to indicate inappropriateness of such materials for practical use without associated technologies to reduce mobilities.
R J Orsler, G E Holland


Seasonal effects of the field evaluation on wood preservatives against mold fungi
1996 - IRG/WP 96-20087
For the purpose of the amelioration of field test methods, commercial preservatives against mold fungi were tested under two different seasons, in winter and in summer. The specimens were bundled and set over the water bath and all these systems were covered with plastic film. At top of the system under film, black films for regeneration of sunlight were put in, and windows for changing air were reserved in summer. The visual evaluation of damage (rating 0-4) was done periodically. The results obtained as follows. 1.) The evaluation values after 2 months in winter were simmilar results as those after 3 weeks in summer. 2.) The fungicides, mixture of nitoril compound and organo nitrogen sulfuric compound, mixture of thiocyanate compound and organo nitrogen sulfuric compound, were obtained good results in field. Those percentage of the specimens rating under 1 were more than 50% and those mean rating were not more than 2. 3.) In the case of organo iodide compound, the results in winter were good but in summer were not so good.
K Suzuki, Y Sugai, K Ryugo, D Watanabe


Effect of asphyxiation on wood decay fungi treated with argon and nitrogen gas
2002 - IRG/WP 02-10452
The effects of low-oxygen conditions, achieved with either argon or nitrogen gas, on the viability of wood decay fungi Coniophora puteana, Antrodia vaillantii and Trametes versicolor, cultivated on PDA medium and infected wood samples, were examined. The fungal cultures were exposed to low oxygen concentration (below 10 ppm) for one to five weeks in hermetically sealed vessels. Anoxic treatment did not affect T. versicolor cultures in the time span of the experiment. Therefore treatment of only C. puteana and A. vaillantii mycelial cultures was extended to 10 and 16 weeks. After treatment, respiration and regeneration of mycelium were tested by measurements of CO2 production and resumed growth of hyphae onto fresh PDA growth medium. The effect of anoxic conditions on the mycelia of treated fungal species was expressed as an increased time needed for regeneration or as a complete absence of growth of inocula taken from the exposed cultures or wooden blocks reintroduced on new nutrient medium. The cultures that were retarded by the low oxygen concentration consequently produced less CO2. For C. puteana cultures, the effects of anoxic treatment became evident in the second week of the treatment. The number of affected cultures rose steadily with the prolongation of anoxic treatment. By the sixteenth week of the anoxic treatment, 80% of the inocula of C. puteana did not regenerate. A. vaillantii inocula regeneration was not affected until after the fourth week of treatment, and similarly for infected wood samples, after five weeks. The influence of anoxic treatment on the cultures of this species was more pronounced on the tenth and especially after the sixteenth week, when 67% of inocula did not regenerate. In general fungal species were differently sensitive to asphyxiation. T. versicolor cultures were not affected by anoxic conditions, caused by either argon or nitrogen gas, and A. vaillantii mycelial cultures proved to be less sensitive than those of C. puteana. In the test with infested wood blocks argon proved to be more effective, compared to nitrogen gas.
C Tavzes, F Pohleven, M Janisek, R J Koestler


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