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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

What information can we glean from field testing
1995 - IRG/WP 95-20057
To mathematically compare the performance of preservatives in a field test, equations were formulated to describe the relation between log score and time and between rate of decay and retention. By combining these equations, a model was derived for the performance of a number of waterborne preservatives. Some relations between the estimated parameters for different preservatives were noted and these were used to develop a universal model to encompass a variety of patterns of deterioration. An attempt was then made to relate these common parameters to the factors known to affect preservative performance. As a result it may be possible to distinguish and quantify parameters specific to the efficacy of the preservative, the aggressiveness of the test site and the characteristics of the wood substrate.
P I Morris, S Rae

Patterns of long-term performance - How well are they predicted from accelerated tests and should evaluations consider parameters other than averages?
1998 - IRG/WP 98-20130
This paper is a discussion of whether different service-life distribution patterns of products treated with unlike preservatives can be predicted, modeled, characterized, or even anticipated from accelerated laboratory tests. Graphic displays of data from Forest Products Laboratory field plots with preservative-treated and fire-retardant-treated stakes demonstrate the importance of local environment as a factor that affects field performance and exhibits differences in dose-response patterns among treatments. These distribution patterns are discussed with reference to early failures, first quartile and median failure times, and distribution about medians. Questions are then asked about the relevance of these parameters to practical applications, about the need to consider population characteristics other than average in evaluations on new preservatives, and about the capability of accelerated tests to estimate these parameters.
R C De Groot, J W Evans

Effect of soil parameters on biocide depletion: laboratory and field studies of water- and emulsion-borne preservatives
2000 - IRG/WP 00-30234
Two field test sites with different soils were selected. Soil analysis showed that the soil at the two sites had considerable texture, base saturation, acidity, and cation exchange capacity differences. Five sets of field stakes were treated as follows: three with water-borne CCA to about 0.4 pcf (6.4 kgm-3) retention, one with 0.75% DDAC, and one with 0.75% DDAC:0.25% chlorothalonil. The last two sets were treated using oil-in-water emulsions. Samples from all five sets were installed at both field sites. In addition, wood samples which had been co-treated with the five sets of field stakes were installed in a lab environment in fungus cellar tubs using soils from the two sites. All wood samples were defect-free southern yellow pine (SYP) sapwood, with the field stakes measuring 19 x 19 x 457 mm3 and the fungus cellar samples measuring 5 x 19 x 250 mm3. The field samples were exposed for two or three years and the fungus cellar samples for 36 weeks, after which depletion of the various biocides was measured. No consistent pattern in CCA depletions between the two soils were observed in either the fungus cellar or field exposure tests, despite the large chemical and physical differences between the two soils. The fungus cellar method may be useful to conduct relatively rapid depletion studies. The authors also discuss problems with depletion studies, including possible influences by soil, wood, and microorganisms present in the soil.
T Schultz, D D Nicholas, D E Pettry, M G Kim

Characterization of checks and cracks on the surface of weathered wood
2000 - IRG/WP 00-40153
The surface roughness of unweathered and untreated pine; unweathered copper chromium arsenate type C (CCA) - treated pine; weathered CCA-treated pine; and weathered CCA-plus-water-repellent (WR) - treated pine was evaluated by a stylus tracing method. Surface roughness parameters Ra, Rz, Rmax, Rk, Rpk, and Rvk were measured. Ra, Rpk, and Rvk were the most appropriate parameters for describing modifications on the wood surface. Ratios of the roughness parameters of the exposed (top) and unexposed (bottom) surfaces of the untreated, CCA-treated, and CCA + WR - treated wood samples were used to estimate the extent of the weathering damage on the exposed surface. The parameter ratios for the top and bottom surface were used to estimate the extent of the damage created by rain and sunlight on each piece of wood. This study shows that the stylus technique is appropriate to estimate the number and size of checks and cracks on wood surfaces after weathering.
D P Kamdem, Jun Zhang

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

Status of Work on OECD Test Guidelines for Emissions of Wood Preservatives to the Environment
2005 - IRG/WP 05-50224-3
In April, 2003, OECD published an ESD on wood preservatives that provides guidance on how to estimate emissions: 1) during the wood preservative application processes and storage of treated wood prior to shipment; and 2) from treated wood-in-service. The ad hoc Expert Group that developed the wood preservatives ESD identified the need to develop Test Guidelines to estimate the amount of biocides leaching from treated wood. A proposal to develop these Test Guidelines was submitted to the OECD Working Group of National Coordinators of the Test Guidelines Programme (WNT), and the WNT agreed at it May 2001 meeting to include this project in the Work Plan and Schedule of Activities. The current work on these Test Guidelines is being carried out b the Secretariat in collaboration with drafting group WG 27 of the European Committee for Standardization (CEN). A first draft of the guidelines (for leaching of active ingredients from wood both in and not in contact with water/soil) was circulated in February 2003 to the National Coordinators for comment. Germany, with funding from the European Commission (EC), had agreed to carry out some pre-validation work that could address some of the issues raised in the comments from the National Coordinators. Germany invited project partners, the OECD Expert Panel, members of CEN TC38/WG 27, industry and governmental agencies to participate in a meeting held in September, 2004 to design the pre-validation work. Once the pre-validation work has been completed and the text for the draft guidelines modified, the guidelines will be submitted to experts in OECD countries for comment. The final drafts of the guidelines will be submitted to the Joint Meeting for declassification.
W Jakob

Influence of different treatment parameters on penetration, retention and bleeding of creosote
2003 - IRG/WP 03-40255
Creosote is an extensively used preservative for transmission poles and sleepers. The purpose of this research was to investigate the treatment parameters necessary to achieve full sapwood penetration and minimum required retention and to avoid bleeding of creosote. It was carried out as a part of the European research project WOODPOLE. Transmission poles of Scots pine (Pinus sylvestris L.) previously air-dried under a roof, were creosote treated in a research plant. Before treatment each pole was cut into three pieces (logs). Each pole made a charge. The creosotes WEI type B and type C were used. A number of treatment processes were carried out using five poles per process. Different levels of pre-pressure and oil pressure were used as well as different duration of oil pressure. Heating of the logs in creosote before pre-pressure and after oil pressure was carried out for one or three hours. Retention was measured by weighing before and after treatment and by analysis. Processes with no or only a short period of heating before pre-pressure and after oil pressure showed most bleeding. Poles and stakes with different levels of retention were produced for field trials.
Ö Bergman

The influence of different creosote process parameters on penetration, retention and bleeding on glulam
2007 - IRG/WP 07-40368
Different process parameters were used to treat Scots Pine glulam beams with creosote. Parameters like pre-heating, pre-pressure time, pressure and pressure time were changed. Most treatments gave a full or almost full penetration of creosote into the sapwood, but the uptake of creosote in the sapwood varies. All samples, except the one with poor penetration, showed heavily bleeding of creosote for about a year before the creosote hardened. To get a good protection of the glulam without bleeding, it has to be double-treated. The lamellae have to be copper impregnated before gluing and the beam must then be treated with a creosote process as C (short pressure time) in part 1. The inner sapwood that will be untreated with creosote will then be protected by the Cu-preservative.
F G Evans

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

Colour change monitoring of photodegradation in Scots pine (Pinus sylvestris) – a short term focus
2009 - IRG/WP 09-40442
Colour change monitoring of photodegradation is a quick and easy method for monitoring rates of photodegradation in timber. A study was undertaken to compare this technique to other monitoring methods, including microtensile strength changes and weight loss. Colour changes due to accelerated sunlight exposure were monitored using a Datacolor check spectrophotometer and compared with a set of controls. Measurements on both samples and controls were performed hourly for the 1st 24 hours and there after daily until 168 hours’ exposure with extra measurements at 200, 350 and 500 hours. A subset of samples, were extracted prior to exposure to check the effects of any colour change due to the presence of extractives. Data was analysed using the reflectance spectra (400-700nm) as well as the CIE-L*a*b* system and ΔE. The majority of colour changes were found to occur within the 1st 24 hours. This was unaffected by the removal of extractives from the wood and was independent of temperature. When compared to the other monitoring methods, colour monitoring has been shown to be the most sensitive method out of the methods compared for monitoring photodegradation in Scots pine.
V Sharratt, C A S Hill, D P R Kint

Critical parameters on moisture dynamics in relation to time of wetness as factor in service life prediction
2014 - IRG/WP 14-20555
The concept of natural durability or enhanced durability based on the presence of active ingredients having an impact on both fungi and insects is not the only parameter steering the material resistance. Complementary resistance to getting wet (wetting ability) and consequently the ease of drying afterwards will lead to a parameter related to the time a piece of wood will remain under such wet conditions that it is prone to decay. Since this concept is merely important for those conditions prone to wetting and drying focus for this complementary material resistance factor is mainly linked to use class 3 applications. This paper gives an overview of 52 wood species, 17 sets of modified wood and 8 wood based panels and the parameters derived from testing according to a protocol soon to become a European standard test method. The method is based on a complementary testing of on one hand floating specimens with a face on water with edges sealed and on the other hand a submersion test with open end grain cross sections. The dimensions are aligned with common field test specimens. Results showed that absorption and desorption figures after 24 hours could differentiate wood species but allowed to classify similar material in the same class. Based on curve fitting this approach can seemingly be improved and also parameters that explain better the water uptake rate and release rates next to total absorption and residual moisture content can be included. In the paper the data are presented using the unit g/m² for the floating test and kg/m³ for the submersion test but these values can easily be translated in percentages moisture content. Future data from continuous moisture measurements will allow underpinning the meaning of the critical parameters in relation to actual time of wetness.
J Van Acker, I De Windt, W Li, J Van den Bulcke

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

Quantifying the effect of microclimatic parameters on the moisture-induced decay risk of wooden structures
2019 - IRG/WP 19-20649
Wood exposed outdoors is prone to fungal degradation. Besides its material-inherent resistance, numerous factors are impacting on its service life with both, climate and design having a major effect. In addition, topography, shading, wind barriers, and other local parameters have an effect on the microclimatic conditions at site and therefore need to be quantified for service life prediction of wooden structures. Within this study we monitored differently severe exposed wooden components, which were implemented in hunting towers serving as test objects on a small but topographically divergent area. The set of instrumented hunting towers showed high potential to deliver the data needed to further quantify the effect of local conditions on the exposure dose of wooden components with respect to topography and canopy. Preliminary data already from the first months of exposure revealed significant differences in exposure-related parameters and the service life of wooden structural elements to be expected under different microclimatic conditions
L Emmerich, C Brischke

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