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Effect of climate, species, preservative concentration and water repellent on leaching from CCA-treated lumber exposed above ground
2001 - IRG/WP 01-50178
Few studies have examined leaching of chromated copper arsenate (CCA) from treated wood in above ground exposures due to the assumption that leaching is less severe compared to wood in continuous contact with soil or water. However, a significant portion of CCA treated wood is used for above ground applications, exposing considerable volumes of the preservative to precipitation and potential leaching. This paper presents preliminary results of a one-year study that continuously monitors CCA leaching from above ground, naturally exposed 5.08 cm x 15.24 cm (2 x 6 inch) dimensional lumber. Three wood species, southern yellow pine (Pinus spp.), jack pine (Pinus banksiana Lamb.), and black spruce (Picea mariana (Mill.) B.S.P.), along with two preservative concentrations and one commercial water-repellent are evaluated for their effect on leaching rates. Preliminary leaching results indicate significant differences between wood species, treating solution concentrations, and the use of water repellent. In addition it appears that climatic variables affect elemental leaching of copper, chromium and arsenic differently. However, the exact effects of climatic variables are inconclusive at this time. Upon completion, this study will offer a substantial amount of leaching data to validate the findings of previous leaching tests, and provide insight into the leaching mechanism of CCA-treated lumber in above ground exposures.
J L Taylor, P A Cooper

In-service performance of wood depends upon the critical in-situ conditions. Case studies.
2008 - IRG/WP 08-20382
Wood is a unique building material, but is by nature designed to deteriorate. A detailed understanding of the factors and interactions involved are important when working with service life prediction of wooden components in buildings. Wood may experience exponential fungal degradation caused by variation in the climatic factors within a small limited area and by minor imperfection in the wooden component. In this paper we put forward a new term: critical in-situ conditions (CIC). This is meant to bring the attention to the importance of looking into details in the construction design, the specific climatic factors and interactions involved. Gaining realistic and useful data for prediction of service life is only possible by controlling and understanding the factors that are target specific for a wooden component or even only a part of it. Performing measurements in a right way and in the proper part of the wooden component are vital for getting useful data for further processing. The objective in this paper is to exemplify the CIC in in-service situations and to describe the factors and interactions that control the service life. Case studies were performed on a building at Bryggen in Bergen, on a hunting cabin on Svalbard, on several wooden windows in the southern part of Norway and on an external wall of a residence house in Ås.
L Ross Gobakken, J Mattsson, G Alfredsen

Climatic impacts on the moisture performance of wooden decking and facades
2013 - IRG/WP 13-20518
In outdoor usage wood is exposed to a variety of influences, which reduce its durability against biological deterioration and wetting. Besides many other factors the service life of wooden facades and cladding is dominated by occurring moisture loads on the one hand and their capability to withstand moisture on the other hand. Hence, climatic factors have a direct impact on the material climate and thus on service life. However there is still a lack of knowledge about the relationship between material climate and climatic parameters. Within this study wood moisture content and wood temperature were recorded for different wood species over a period of 34 months. By means of a dose-response-performance model the moisture and temperature dependent dose was determined for different wood species, orientations and expositions. The respective dose-time functions were calculated and expected service lives estimated. Relations of the service life to specific wood species, orientation and exposition were identified. For claddings oriented to the south higher dose values were induced compared to claddings oriented to the north. Also the horizontal exposition experienced higher moisture loads compared to the vertical. Furthermore differences between different test sites were determined and could be explained with different climatic loads impacting on the construction. Driving rain loads led to higher moisture levels in the claddings. Furthermore the wood moisture content was found to be influenced by RH levels and increased temporarily after rain events. During the summer period with higher air temperatures redrying was fostered and lower dose values were induced. No significant relationship between the sorption behavior of different wood species determined under laboratory conditions and their respective moisture performance in the field was found. However, a general trend could be deviated, which showed that the higher the wetting ability of wood the lower was the determined resistance against fungal degradation. The variation between the sorption behavior of the different wood species was not interconnected to the moisture performance or decay resistance of the respective wood specie in the field. It is recommended to take more advantage of the additional information provided by continuous MC measurements, in particular with respect for service life prediction issues. They can provide additional information about the respective material itself as well as about its performance in different exposure situations.
T Bornemann, C Brischke, G Alfredsen

Effects of climatic factors and material properties on mould growth on untreated wooden claddings
2017 - IRG/WP 17-10884
Mould growth is an important contributor to colour change of untreated wood exposed outdoors. Predicting the development of mould growth is therefore important to ensure successful use of untreated wood as a façade material. More knowledge about the factors affecting mould growth on outdoor exposed wood is required to give better predictions. In this study, climatic factors and material properties affecting mould growth have been investigated by exposing selected wooden specimens (aspen, pine sapwood, pine heartwood, spruce sapwood and spruce heartwood) to 8 different climates for 91 days. The climates were defined in a factorial design with two levels of relative humidity (65 and 85 %), wetting period (2 and 4 hours per day) and temperature (10 and 25 °C), respectively. The degree of mould growth was visually evaluated once a week during the exposure period. Aspen and pine sapwood were the substrates most susceptible to mould growth. There were no significant differences in susceptibility between pine heartwood and spruce heartwood, but the difference between heartwood and sapwood was significant for both pine and spruce. The effect of density on mould growth was tested for the spruce heartwood material, but was not found to reduce the residual variance significantly. However, all the tested climatic factors affected mould growth significantly; relative humidity was most important, while there was a somewhat smaller effect of wetting period and a minor effect of temperature. Overall, increased RH, longer wetting period and increased temperature had a positive effect on the mould growth. It was found a significant interaction between temperature and relative humidity, indicating that the temperature had larger effect on the mould growth at lower relative humidity, and that the relative humidity had larger effect at lower temperature. There was a tendency that the relative performance of the substrates was dependent on climate, but this interaction effect was not significant for any of the climatic factors.
S Karlsen Lie, G I Vestøl, O Høibø, L Ross Gobakken

Degradation of Eucalyptus transmission poles varies across regions in Zambia
2018 - IRG/WP 18-30727
Evidence from literature shows that Eucalyptus poles treated with creosote last over 30 years before replacement. However, in Zambia, the life span of such poles has reduced to 5-10 years. The aim of this study was to investigate factors associated with degradation of treated Eucalyptus poles and how these varied across regions in the country. A total of 1200 poles were assessed in three different climatic regions. The annual rainfall (mm) differed significantly between regions (i.e. region I < 800, region II 800-1200 and region III >1200). Degradation also differed significantly between regions (F2, 28 = 12.5, p < 0.001) with high proportion of degradation observed in region III (61.0 ± 2.6) and low proportion in region I (39.5 ± 3.8). The Pearson correlation between degradation and rainfall was significantly positive (r = 0.579, p <0.01) while the correlation with temperature was negative (r = -0.20, p>0.01). These results suggest that high rainfall areas experienced high degradation of creosote treated transmission poles in the country. This is not surprising because creosote is known to leach in high rainfall areas thereby exposing poles to agents of degradation. Our results reveal that degradation of Eucalyptus transmission poles in Zambia is a function of rainfall. Therefore, in order to increase service life of poles, preservative treatment systems should be adjusted and tailored to end use, depending on the characteristics of the region where the poles will be used. The detection, identification, fungal richness and density of termites across climatic zones are recommended for further investigations.
P Ng’andwe, D Chungu, E Ncube

Occurrence of synanthropic beetles (Coleoptera Ptinidae) and checkered beetles (Coleoptera Cleridae) in relation to climatic factors in historical buildings from North-Eastern Germany
2021 - IRG/WP 21-10980
Predatory checkered beetles occur in many historical buildings. Thus, it is essential to learn more about the ecology of these beetles, specifically for their further use as suitable beneficial organisms in biological control of wood-destroying insects. In this study, indoor climatic conditions were examined as a major factor influencing their occurrence and that of their prey Anobium punctatum and Xestobium rufovillosum. For this purpose, monitoring and climate measurements were implemented in nine historic buildings in North-Eastern Germany (Mecklenburg-Vorpommern). A collective occurrence of Opilo domesticus and Korynetes caeruleus together with the wood boring pests was shown via sticky traps and collections of adult beetles. The exit holes of O. domesticus and Opilo mollis in paper covers used to monitor hatching-activity are not sufficiently species-specific and are therefore not considered in the evaluation of the climate data. Usually only annual and monthly mean values for temperature and relative humidity have been considered to discuss the occurrence of the insects mentioned. Anobium punctatum and X. rufovillosum, as well as their predators K. caeruleus and O. domesticus, have been found in half-timbered and solid structures. According to this, their climatic requirements must be quite similar. As a new study approach, climatic conditions for the period of walking and flight activity (reproductive phase via sticky traps and collections) were studied separately for both, the beneficial insects and wood pests. The results obtained so far partially showed significant differences for the insect species investigated. Anobium punctatum reproduces within narrowly defined temperature intervals with an optimum between 15.5 - 18 °C. For the reproductive phase of O. domesticus, the optimal temperatures are between 16.5 - 18 °C, up to about 23 °C, which almost exactly corresponds to those of A. punctatum. However, there are differences in humidity requirements. The beetles of O. domesticus have only been recorded at a rel. humidity of 64 - 73 %. This range of rel. humidity is narrower than for A. punctatum, whose beetles are found in buildings with rel. humidity from 55 - 80 %. These differences in climatic requirements may be part of the reason for the less frequent occurrence of O. domesticus beetles in only three buildings and the greater distribution and abundance of A. punctatum in all nine buildings. The obtained results from these studies and those of previous findings regarding climatic conditions will help successful breeding of checkered beetles in the laboratory for biological control purposes.
C Baar, C von Laar, M Willert, H Bombeck