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Improving our understanding of moisture and other durability-related properties of wood in building envelope performance prediction
2011 - IRG/WP 11-20468
Building science has become an increasingly important field in recent years with rapid changes in construction methods, building materials and consumer expectations. The field has also been brought to prominence by a few large-scale premature building envelope failures in a few regions across the world. Considerable effort has been put into developing hygrothermal models to simulate heat, air, vapour, and water movements within and through building envelopes. A few have become popular design and research tools for predicting and evaluating durability performance of building assemblies. One of the building elements which have often been put under building scientists’ microscope is wood, given the traditional uses and the newly expanded use of wood in building systems. Therefore it has become more and more important to bridge the gap between wood science and building science and carry out interface research to understand the behaviour of wood in modern building envelopes. One simple example concerns the relationship between equilibrium moisture content (EMC) of wood and relative humidity (RH) in the environment. Pressure plate methods have been commonly used in building science laboratories to measure EMC under near-saturated RH conditions. It was found that this method could result in unrealistically high EMCs if there is a lack of understanding of the unique characteristics of wood structure. Meanwhile the commonly used assumptions of EMC under changing RH conditions based on simple sorption curves may lead to unrealistic prediction of service moisture content. Another example is related to the consequences of service moisture conditions. Hygrothermal models are often designed to predict durability performance such as mould/decay growth and metal corrosion based on the predicted humidity or moisture content. Realistic prediction requires realistic mould/decay data as well as appropriate application of the data for specific conditions. This paper reviews topics where the wood science community can usefully work with the building science community and help each other better understand wood and improve the wood use in construction.
Jieying Wang, P Morris


Hygrothermal performance of ventilated wooden cladding
2016 - IRG/WP 16-40733
The risk for an attack of wooden claddings by decay and discolouring fungi strongly depends on the moisture and temperature conditions in the building envelope. The design of the cladding has a major influence on its hygrothermal performance. In the present study, different wooden ventilated cladding designs were investigated at a test house in Mid-Norway for four years. The objective was to increase the understanding of the relation between microclimatic conditions and the responding hygrothermal performance of the wooden claddings concerning their cardinal directions, the design of ventilation gap at the bottom and top of the cladding, the wood material quality, and the surface treatment. A statistical analysis revealed that air temperature, global radiation, and wind velocity were the three main factors that influenced wood moisture content (MC). Wind driven rain (WDR) was only the fourth most important factor. WDR only defines moistening and not drying, which might explain that WDR did not rank higher as explaining factor for MC. The importance of the wind velocity led to a separate computational fluid dynamics study (CFD) of the airflow in the cavities of the ventilated cladding. The study resulted in a function describing the airflow change rate of the ventilated cavities dependent on the wind velocity, wind direction, and cavity opening. The test house study shows that only 4 mm opening at the bottom and top of the ventilated cavity significantly reduces the risk of moisture problems in the wall assembly. Further opening to 23 mm did not give further improvement in a moist climate. In a dry climate, a design with closed ends of the cavity results in lowest MC. No significant conclusion can be drawn regarding the surface treatment (acryl vs. alkyd) and material quality (fast-grown spruce vs. slow-grown spruce). The test house measurements were used for validation in Heat, Air and Moisture (HAM) simulations of wooden claddings. The model showed good correlation to measurements and enables simulations to find the best-suited cladding design for different climates.
K Nore, U Hundhausen


Comparative performance of wood/wood-based claddings predicted by four hygrothermal simulation tools
2019 - IRG/WP 19-20646
A number of hygrothermal numerical simulation packages are available, either wholly or partially dedicated to heat, air and moisture transfer simulations of building materials and wall assemblies. The objective of this work was to compare the hygrothermal responses and the moisture performance of western red cedar and composite wood claddings of a wood frame wall as predicted by four hygrothermal simulation tools: DELPHIN, WUFI, hygIRC, and Comsol. Three Canadian cities having different climates were selected for simulation: Ottawa (ON), Vancouver (BC) and Calgary (AB). In each city, simulations were run for two years as selected from a historical climate data set based on the moisture index. The wall orientation receiving the most wind-driven rain for the two years were selected for simulations. Material properties were taken from the NRC material property database. Cladding temperature and relative humidity values as well as the moisture accumulated in the entire structure were compared amongst the results obtained from the four tools. Mould growth index on the cladding surface was used as a basis for comparing the moisture performance predicted by the tools. Temperature profiles on the cladding surfaces in the three cities considered were all in good agreement for the four tools. For composite wood cladding, all four models gave similar trends for relative humidity and for each of the three cities. However, WUFI tends to predict higher relative humidity as compared to results obtained using either DELPHIN, Comsol or hygIRC. For red cedar cladding, hygIRC predicts higher relative humidity than that predicted by other tools in Ottawa and Vancouver. Simulation results obtained with constant wood properties suggest that amongst other factors, material property processing may explain these discrepancies. Results for total accumulated moisture in the structure showed that WUFI tends to accumulate more moisture in the structure than other tools, which is probably related to how WUFI computes the absorbed wind-driven rain at the cladding surface. The predicted values of the mould growth index over the two-year period by the four tools were all below the threshold of 3 (no visible mould growth), but in general, WUFI provides more conservative predictions, offering higher values for mould risk as compared to the other tools.
M Defo, M Lacasse, A Laouadi


Proposed method for out-of-ground contact trials of exterior joinery protection systems
1981 - IRG/WP 2157
Methods for testing the efficacy of preservative treatments for exterior joinery are described using the format of a European Standard. Commercially used treatments applied to jointed test units (L-joints) which are then protected by conventional finishes are exposed to normal outdoor hazards out of ground contact. Assessment is made a) by determining eventual failure through decay and b) by destructive examination of replicate treated and untreated units, after increasing time intervals, rating comparative performance in terms of wood permeability increase and the progress of microbial colonisation.
J K Carey, D F Purslow, J G Savory


Field performance of wood preservative systems in secondary timber species
1997 - IRG/WP 97-30152
The objective of this ongoing study is to evaluate the performance of new, potential, and standard wood preservative systems in secondary North American timber species. Eleven preservative systems were evaluated in this study - ACQ Type B, Copper Citrate 2: l, CDDC, chlorothalonil/chlorpyrifos, copper-8-quinolinolate, tebuconazole/chlorpyrifos, RH287, propiconazole/chlorpyrifos, copper naphthenate, CCA. and creosote. Field evaluations are being performed with ground contact field stakes and termite-specific testing in Hawaii, along with laboratory soil bed tests. The major wood species used with all the systems and evaluation methodologies are loblolly pine, northern red oak, tulip poplar, and cottonwood. More limited evaluations (field stakes only) are being conducted with eastern hemlock, red maple, and sweetgum. Information is presented from laboratory soil bed, field termite, and field stake evaluations. There is good correspondence between soil bed and field stake results. The more highly developed preservative systems and those in an AWPA P9 Type A oil carrier tend to perform better, and there can be a strong affect on performance from the wood species.
P E Laks, K W Gutting, R C De Groot


How to Document the Performance of Super-Critical Treated Wood in above Ground Situations?
2005 - IRG/WP 05-20316
The paper presents practical experiences from the preparation of a new preservative treated wood product for introduction to the market. The product in question is Superwood™, which is treated with organic biocides using CO2 in a supercritical state as a solvent. The question is how to evaluate the performance of a new product such as Superwood™ in order to get an acceptance on the market and fulfil the formal requirements. In the European Union countries, the EN 599-1 is the standard that needs to be complied when approving a new product for the market, but it only focuses on the toxic limit against representative decay fungi according to EN 113. However, decay test, above ground and other forms of field tests are optional, this is not in line with the traditional test philosophy in the Scandinavian countries. The open question is to which extent treatment to the level of the toxic threshold value also ensures a long service life and expected performance of the treated commodity. Superwood™ is evaluated using a strategy, in which basic laboratory tests are done to get the toxic value (according to EN 599-1) and in addition a number of field tests are done including accelerated testing in the tropics. These tests are focussed on the evaluation of the performance criteria such as durability and service life and maintenance requirements. These questions must be answered by the producer without having a full record of performance test for their new products. A short status on the test performed on super-critical treated wood (Superwood™) is presented. Based on a comparison between field test in Scandinavia and in the tropical Malaysia a service life of more than 25 years for a specific supercritical treated product is estimated. It is stated that the existing European standardisation system is insufficient when it comes to service life prediction. A number of important questions need to be addressed by the European standardisation system as soon as possible because the market and the public opinion change quickly due to environmental concern.
N Morsing, A H H Wong, F Imsgard, O Henriksen


Performance of treated fence posts after 6 years in five test plots in the State of Sao Paulo - Brazil
1976 - IRG/WP 376
Fence posts treated with creosote, pentachlorophenol and creosote/ pentachlorophenol mixtures showed good performance after 6 years of exposure in five test plots located in the State of Sao Paulo - Brazil. Good results were also achieved with copper sulphate/sodium arsenate and copper sulphate/potassium dichromate mixtures. Fungi and termites were the main destroying agents found attacking the posts.
M S Cavalcante


Performance of preservative-treated hardwoods with particular reference to soft rot. Report of condition of specimens installed in Victoria, Australia
1980 - IRG/WP 3155
J Beesley, R McCarthy


The long-term performance of boron treated joinery in service - A case study
2000 - IRG/WP 00-20208
Joinery treated with borates 23 years ago and in service in residential flats was surveyed and analysed for boron content. The levels of boron still present were sufficient to prevent decay. None of the windows surveyed showed any decay despite the fact that moisture and sapwood contents were conducive to decay.
D J Dickinson, R J Murphy


Effect of a penta emulsion on the service life of Douglas fir, heartwood posts
1978 - IRG/WP 3112
C S Walters


European standardization for wood preservation
1989 - IRG/WP 2335
G Castan


Comparison of Different Methods for Assessing the Performance of Preservatives in the BAM Fungus Cellar Test
1998 - IRG/WP 98-20149
The fungus cellar test is a common means to get reliable data on the long term performance of treated wood in soil contact. A constantly high humidity and a suitable of water holding capacity for a range of micro-organisms provide high decay rates in untreated wood and produce intensive microbial pressures on wood treated with biocides. Presently a range of biocides are under test in the BAM fungus cellar and the results will be presented for the following types of biocides: Tebuconazole in combination with copper and boron (5 years fungus cellar), quats with copper and boron (5 years fungus cellar) and Cu-organic compound combined with copper and boron (3 years fungus cellar). Figures will be shown on the development of the Modulus of Elasticity (MOE) over the years and on an assessment of the stakes according to EN 252.
I Stephan, M Grinda, D Rudolph


Copper naphthenate performance: A new way to look at old data
2000 - IRG/WP 00-30215
Although copper naphthenate has over a 50-year test history, it is still considered as a "new" preservative in the United States when it is used for utility poles. It has also been extensively used in remedial treatments for poles and has considerable retail or over-the-counter sales. The test history includes a number of different tests and a rationale for evaluating this data and comparing the performance of copper naphthenate to other common pole preservatives is presented. Thus, the efficacy of copper naphthenate can be easily summarized.
C R McIntyre


In-ground performance of two formulations of chlorothalonil after five years of exposure at three test sites in Australia
1996 - IRG/WP 96-30101
Sapwood specimens of Pinus radiata D. Don and Eucalyptus regnans F. Muell. were each treated to three retentions of each of two preservative formulations (chlorothalonil in oil; chlorothalonil plus chlorpyrifos in oil) and installed in-ground at three field test sites in Australia. Specimens were treated with each formulation to achieve 3.2, 6.4 and 12.8 kg/m³ of chlorothalonil a.i. and 3.2 + 0.2, 6.4 + 0.4 and 12.8 + 0.8 kg/m³ of chlorothalonil plus chlorpyrifos a.i. For comparison, specimens of each timber species, treated to a commercial in-ground retention of a copper-chromium-arsenic (CCA) formulation, were also installed. Treated specimens (including controls) have been rated for their condition annually for attack by subterranean termites and fungal decay using a scale ranging from 4 (sound) down to 0 (failed). After five years of exposure, mean termite and decay scores for replicate test specimens at each site reveal that the performance of all three retentions of each formulation, particularly the two highest retentions, is comparable to CCA.
J W Creffield, T L Woods, N Chew


Performance of Tebbacop in laboratory, fungus cellar and field tests
2000 - IRG/WP 00-30222
A novel organo-copper wood preservative ("Tebbacop") has been exposed to 12 years fungus cellar testing and 6 years above ground field testing. In the fungus cellar, Tebbacop at a retention of 0.053% Cu m/m oven dry wood out-performed CCA at a retention of 0.55% m/m oven dry wood. In above ground tests, L-joints treated to a Tebbacop retention of 0.012% Cu are performing as well as joints treated with TBTN to a retention of 0.08% Sn. In a slightly more severe decking test, 0.016% Cu as Tebbacop was more effective than 0.08% Sn as TBTN.
M E Hedley, D R Page, B E Patterson


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


Possibility of use of wood species per class of biological risks. Attempt to determine criteria based on Pr EN 350-1/2/3
1992 - IRG/WP 92-2409
M Rayzal


Performance results of wood treated with CCA-PEG
1986 - IRG/WP 3363
The addition of polyethylene glycol (PEG) to the CCA system has been shown to reduce the surface hardness of poles and ease spur penetration during climbing. This paper addresses the results of tests dealing with preservative retention and penetration, permanence of CCA and PEG, strength, drying rate, and checking characteristics.
W P Trumble, E E Messina


European standardization for wood preservation
1990 - IRG/WP 2359
G Castan


Performance of untreated French Guianan piling in marine exposure
1992 - IRG/WP 92-4173
Round piling of seven French Guianan species, greenheart, and preservativ-treated Southern Pine were installed as fender piling in Key West, FL. After 12½ years, none of the tropical hardwoods performed as well as dual-treated Southern Pine. Of the hardwoods, kouata patou and maho noir were the most resistant to decay and marine borers.
B R Johnson


Efficacy of anhydrides as wood protection chemicals - II. Performance against soft rot fungi
1998 - IRG/WP 98-30174
Pine sapwood modified with various anhydrides and with butyl isocyanate was tested for its resistance to soft rot decay. Small stakes were exposed for 20 months in unsterile soil in a fungal cellar test. Wood modified with butyl isocyanate performed better than any of the anhydrides tested, with a threshold level of protection (less than 3% weight loss) at 12% weight percent gain (WPG). Stakes acetylated to 15% WPG did not give complete protection against soft rot. Stakes modified with alkenyl succinic anhydride showed increasing resistance to soft rot with WPG up to about 10% WPG, above which no further improvements were evident. Succinic anhydride and phthalic anhydride treated stakes showed little or no noticeable protection.
S C Forster, M D C Hale, G R Williams


Are fungal cellar tests really necessary?
1989 - IRG/WP 2333
During the past decade the range of methodology used to evaluate wood preservative potential has significantly expanded. At the forefront of these new tools available to the scientist·is the fungal cellar. This technique, as currently applied, involves the exposure of treated and untreated samples to conditions of moisture and temperature which ensure optimum fungal attack. By comparison data with that obtained on similar preservative systems in conventional stake tests, acceleration factors for predicting performance have been developed. This discussion paper examines the philosophy influencing the development of fungal cellar testing, and provides an alternative viewpoint.
J N R Ruddick


Biological performance of gypsum products containing borates
2000 - IRG/WP 00-30237
At suitable retentions borates have biostatic properties enabling them to be used for biodeterioration control in wood. They provide protection against decay fungi, mould, and termites, which are known to also attack gypsum products. Currently, many gypsum products contain added borates, which are used to improve physical and processing characteristics. Work examining the effect of borates at controlling biological attack in gypsum products is presented in this paper. Gypsum or gypsum board with different borate loadings was tested for its performance against dry rot, mould, and subterranean termites in order to see if current commercial levels of borates used in gypsum products would also render them resistant to these common types of biodeterioration. It was confirmed that the presence of borates significantly decreases the amount of biological attack found in gypsum products. From the results obtained it can be concluded that the addition of borates to gypsum products provides more than simple mechanical and processing improvements. For complete biodeterioration control however, especially against mould, higher retentions should be considered. This knowledge could have great significance in the near future, with moves to require termite resistant construction materials (including gypsum board) in some areas and the rising concern of illnesses associated with 'sick building syndrome' caused by in-house mould growth.
J L Fogel, J D Lloyd


Above ground performance of CCA-treated fingerjointed lumbe
1993 - IRG/WP 93-40003
Studs made from short lengths by finger jointing are becoming more commonly used in North America. Recently Forintek has received enquiries about the performance of such material in a treated form. Treated and untreated nominal 2x4 inch² spruce-pine-fir (SPF) studs exposed above ground for 12 years in southwestern British Columbia were evaluated for evidence of decay. Despite shallow preservative penetration, which did not meet North American standards, the CCA-treated material showed no signs of decay. In contrast two of the 30 untreated samples had failed and the mean rating was 1.3 on a 0 to 4 scale. These results are encouraging for the use of CCA treated SPF as finger jointed or conventional lumber in above ground exposure.
P I Morris, G E Troughton


Report of the meeting of the refractory timbers sub-group, Lappeenranta, Finland on 25 May 1989
1989 - IRG/WP 3561
The first meeting of this sub-group took place on Thursday 25 May and considered the following agenda: 1) Papers presented to the meeting "Performance of treated spruce in Canadian field test sites" by J.P.Hösli and E.E.Doyle, IRG/WP/3506 and "Performance of CCA treated spruce and pine in unsterilized soil" by A.J.Nurmi. 2) Future work areas for the sub-group 3) Membership of the sub-group 4) Circulation of information
R J Murphy


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