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Finishes for outdoor timbers
1975 - IRG/WP 378

Exterior wood stains
1980 - IRG/WP 3135
Experience has shown that conventional paints cannot now be relied upon to provide a complete seal against water entry, that in practice water can often circumvent the film and that the paint, far from serving to keep water out will seal it in. Moreover present-day paints are often subject to localised and premature failure out of doors and consequently entail high maintenance costs. Problems of wood decay and premature paint failure reached a high level during the 1960s, and led to the acceptance of the need for the preservative treatment of softwood joinery and cladding. The question remains however, whether, in the light of changes in the quality of timber and how it is used, the traditional approach of attempting to seal the outer surface of the wood is still valid, or should be abandoned in favour of using different types of finish which are more permeable to moisture and prevent it accumulating in the timber. One of the reasons for the remarkable success of semi-transparent exterior wood stains is that they met the demand for finishes of increased water vapour permeability for timber which was susceptible to decay. They also possessed two other important attractions: they provided natural finishes for exterior timber which were without the technical problems of clear varnish; and their mode of breakdown by erosion reduced the preparation work in maintenance and hence the overall maintenance costs. These are valid commendations for stains and remain important factors encouraging their use. Stains offer the architect additional design freedom and, used effectively, can make a pleasing contribution to the appearance of modern buildings. They do reduce average moisture levels in the timber and are simple to maintain, though these advantages may be offset to some extent if more frequent maintenance is necessary and if the higher permeability creates problems from dimensional movement.
E R Miller

Novel wood modification processes for window and cladding products
2004 - IRG/WP 04-40285
Because of the low natural durability and low dimensional stability of European wood species, the usage of wood for window frames has decreased dramatically during the last decade. In a joint project of several German research institutes and the window industry, following wood modification systems were compared. heat treatment (3 different materials from 2 companies) acetylation (pine sapwood and beech wood acetylated with acetic anhydride) polymerisation (melamine resin treated pine sapwood, Interlace treatment, furfurylation) wax treatment (pine sapwood, which was impregnated with natural resin and waxes) Investigated was the moisture content, dimensional stability, capillary water uptake and the durability. The dimensional stability show a high increase for following materials: heat treated wood, acetylated pine, interlace treated wood and furfurylated wood. The melamine resin treated wood and the wax treated wood show no significant increase in the dimensional stability. The biological durability against different basidiomycetes was tested according to the EN 113. As test fungi, Coniophora puteana, Poria placenta and Coriolus versicolor were used. The results show a very high increase in the durability for most of the treated wood. The wax treated wood shows no significant increase in durability. A novel window frame consists of several functional layers. Different wood properties are demanded for the single layers to achieve optimal window properties. Every modified wood shows a special potential for the use in a functional layer.
A Krause, C Hof, H Militz

Surface coatings for impregnated wood
1992 - IRG/WP 92-3684
The use of proper surface coatings enhances the aesthetic and protective properties of impregnated wood. Good results with especially water-borne coatings have been obtained for class-A impregnated L-joints and claddings in field tests started in 1982.
L Kotama

Durable fibre for durable MDF – testing Tricoya®
2015 - IRG/WP 15-40704
The chemical modification of wood has been a commercial reality for a decade on release of technologies for the modification of solid wood including Accoya®. A challenge and an opportunity for the modification technologies which typically impart dimensional stability, water stability and enhanced biological durability was the adaptation of the technology to wood based panels. This paper presents a summary of the development of Tricoya®, its testing and performance and examples of applications.
E Suttie, J Alexander, M Maes

A real scale evaluation method and results on termite resistance of housing wall systems and floor framings
1999 - IRG/WP 99-10314
For evaluating the termite resistance of real scale houses especially housing wall systems and floor framings, a experimental building was prepared. After initial feeding of termite, this house was constructed. In this experimental building, several parts which were built by different wall systems and floor framing. The room temperature of these parts were controlled. Water can be provided in the wall systems. Well termite installed feed log was inserted in each wall system. After 2 weeks, the difference of agregation can be observed. By this experimental building, the termite resistance of housing system can be classified.
K Suzuki, K Okada, K Hagio, Y Tanaka

Service Life Prediction of Wood Claddings by in-situ Measurement of Wood Moisture Content: Status after 5 years of Outdoor Exposure
2009 - IRG/WP 09-20401
The Danish Technological Institute is in co-operation with industry partners running a project aiming at predicting the service life of different wood protecting systems. The project focuses on examining the moisture reducing effect of different protecting systems for timber claddings and the ability of these to maintain the appearance of the surfaces, when the wood is used in service class 3 (EN 335-1 1992). A façade construction is exposed to weathering at the field test area of the Danish Technological Institute (near Copenhagen). In specific locations of the construction measurements of wood moisture are done by in-situ resistance moisture meters (Lindegaard and Morsing 2006). The aim is that the test should form the basis of evaluation of the maintenance requirements and the prediction of service life of the surface treatment and the wood/construction. At the moment 60 test racks are exposed. This study examines the data from the first five years of outdoor exposure using data from a test rack with a water-borne acrylic coating and a test rack with ICP coating for case studies. The moisture content data was converted into weekly average and weekly variation values which gave a deeper insight into the performance of the tested systems. The first was used to check for moisture build-up in the construction whereas the latter gave an indication of the gradual degradation of the coating itself, i.e. the degree of cracking. A linear tendency with time was found for all tested systems and the maintenance period could be estimated on the basis of data from only 2-3 years of outdoor exposure. The risk of biological degradation was evaluated using 20 % MC and 10 °C as a limit below which the risk was negligible. The annual accumulated time above this limit was used as an indication of the risk of biological degradation. Data was corrected for variation in weather exposure between the years and a fairly linear tendency in time was found, i.e. the risk of biological degradation was found to increase in time for all tested systems. Furthermore, other combinations of moisture content and temperature were used as limits enabling a more detailed view of the risk pattern. In general, it was found that measuring the moisture content in-situ in a façade construction of the suggested design can be a valuable tool in service life prediction. Within reasonable time, it is possible to obtain enough data to predict the service life of the construction in terms of maintenance period and the risk of biological degradation of the construction.
E Tang Engelund, B Lindegaard, N Morsing

A fast and economic method to produce grey wooden surfaces for decking and cladding: preliminary results
2009 - IRG/WP 09-40474
Uncoated wood is commonly used in France for cladding and decking to minimise maintenance. However wood surfaces progressively turn grey due to exposure to sunlight and water. This grey colour develops after several months depending on the wood species and the exposure: in the northern hemisphere surfaces facing south and west are most exposed and turn grey more rapidly than those facing north and east. The result is unfortunate differences in the appearance of the building which obviously is not appreciated by the end-users and which leads to a negative image of the wood material. As a consequence of this some architects would like to have grey wood right from the beginning of the construction. Producing grey wood using artificial weathering devices or natural weathering exposure is possible but too expensive and too long. In this project the idea is to develop a non-film forming coating whose colour is similar to the grey appearance produced by the natural weathering. This coating must be durable enough just to allow a soft transition between its own degradation and the development of the grey colour produced by the natural weathering.
L Podgorski, V Georges, I Garmendia, B Sánchez Sarachu

Service life prediction of wooden components – Part 2: Impact of material, exposure and design details
2010 - IRG/WP 10-20440
Dose-response functions permit to estimate the moisture and temperature induced decay potential for any wooden building component and exposure, and thus the service life to be expected. In part 1 of this series dose-response functions were established as a result of double layer field trials carried out at 24 European test sites over up to eight years. Using them makes it no longer necessary to conduct field trials as long as decay actually occurs. They allow determining dose-time functions for a certain construction detail over shortened time periods (2 3 years). Within this paper we present the test set up of different studies aiming on quantifying the impact of material, exposure and design details on the service life to be expected for wooden components. Therefore long-term moisture recordings were applied to different wooden commodities, e. g. fence posts, pickets, decking, and facades. Furthermore, the impact of orientation, distance to the ground, and driving rain load on facade panels was studied. Finally dose-time functions will be recorded for ten different wood species used in horizontal and vertical orientation. First results from the various studies including preliminary service life estimation for various components are also presented.
C Brischke, B Lauenstein, M Bilstein, T Bornemann, A O Rapp

Service life prediction for exterior timber cladding
2010 - IRG/WP 10-20460
This discussion paper considers service life prediction for timber and the work within the pan-European WoodExter project. The project aims to develop a model for service life prediction of exterior timber cladding, to enable better end use selection of material suitable for delivering the required service life of cladding and to provide information for professionals wanting to understand and use timber cladding. Service life prediction of buildings is discussed in the context of ISO 15686 the international suite of standards for service life prediction. The challenges that are ahead to enable a successful predictive approach to be developed are considered.
E Suttie, F Englund

Aesthetic service life of coated and uncoated wooden cladding - influencing factors and modelling
2011 - IRG/WP 11-20470
Mould growth on exterior coated cladding façades is an undesirable element and will often shorten the aesthetical service life. Mould growth on painted surfaces is influenced by type and concentration of film fungicides, the paint formulation and the wood substrate itself, and wooden cladding may experience exponential fungal deterioration caused by variation in the climatic factors, often within a small limited area. The objective of this study was to gain knowledge about which factors influence surface mould growth on coated and uncoated wooden cladding in an outdoor environment, with a special attention to modified wood substrates. The data are based on evaluation of mould growth coverage on outdoors exposed wood panels consisting of different combinations of wood substrates and surface finishes. Panels were exposed on three locations; Bogesund (Sweden), Birkenes and Sørkedalen (Norway). The panels were monitored up to 4.5 years. The analysis showed that coating typology and exposure time both had highly significant influences on mould growth. Furthermore, wood substrate, temperature and relative humidity had a significant influence on mould growth, but comparatively less than coating typology and exposure time. Siberian larch heartwood, copper-organic preserved Scots pine and Scots pine heartwood performed best among the wood substrates. Heartwood as wood type was less susceptible to mould growth than a mix of sapwood and heartwood wood and pure sapwood. Acetylated Scots pine as wood substrate and Aspen as wood species had lower resistance to mould growth than the other wood substrates and wood species, respectively. The physical surface structure of a paint film also influences the mould growth. A hard model paint was significantly more susceptible than the other model paints. A soft model paint performed best, with the least mould growth coverage. Aureobasidium pullulans (deBary) Arnaud was the dominating fungal species on all the wood substrates.
L Ross Gobakken, O A Høibø

Moisture protection and performance during 5 years exposure of 19 wood coating systems on a cladding in Vienna
2011 - IRG/WP 11-40561
A cladding with vertical boards of Norway spruce (Picea abies) comprising different coating systems had been exposed to natural weathering oriented south west in Vienna for 5 years. Weathering behaviour of the boards was assessed in intervals and wood moisture content was measured over the first 22 months of exposure. The moisture protective properties of the coating systems were assessed using laboratory methods. The results of weathering behaviour indicated higher coating durability with higher dry film thickness and lower transparency of the coating systems. The coating systems provided a certain degree of moisture protection that was influenced by paint colour, water permeability and surface roughness. Panels with low permeable coatings showed a better performance in natural weathering.
G Grüll, I Spitaler, M Truskaller

Effects of microclimate, wood temperature and surface colour on fungal disfigurement on wooden claddings
2012 - IRG/WP 12-20490
Wooden claddings are common in façades in Norway, and Norway spruce (Picea abies) is the most frequently used species. The cladding is a major part of the facade, and it has visual requirements that may define the aesthetic service life. The visual changes that occur during weathering can be colour changes, abrasion or wear, blistering, flaking, and even cracks in the wood or coating, but more often growth of mould and blue stain fungi are the main challenge. A field test with synchronous monitoring of relative humidity, air temperature, material temperature and wood moisture content in Norway spruce claddings has been established in southern Norway as part of the ClimateLife project. Visual evaluation of blue stain and mould growth according to EN 927-3 was performed, and evaluation data after 10 months exposure is presented. The objectives were to study the effect of 1) environment, 2) cardinal direction and 3) colour of the cladding on growth of blue stain and mould fungi, and further study the variation in relative humidity, air temperature in front of a surface and the material temperature due to change in 1) environment, 2) cardinal direction and 3) colour of the cladding. After 10 months exposure, the red coating system had lowest mould ratings and the uncoated claddings had the highest. Claddings facing south tend to have higher mould ratings than those facing north. No difference was found between shaded and open environment. The relative humidity was higher in front of the claddings exposed in a shaded environment compared to an open environment, and in an open environment the relative humidity was lower against south than north. The temperature in front of the red coloured claddings was highest. Except for the red-coated claddings, the air temperature was higher than the material temperature.
L Ross Gobakken, G I Vestøl

Field-testing of Norway Spruce Claddings with Monitoring of Moisture Content, Material Temperature and Microclimate
2012 - IRG/WP 12-20502
The physical function of a cladding is to protect the interior construction. Under normal circumstances the performance requirements can be met for a very long time, meaning that the technical service life of a wooden cladding can be very long. Since the cladding is a major part of the facade, it also has visual requirements that may define the aesthetic service life, and often it is much shorter than the technical service life. The visual changes that occur during weathering may be colour changes, abrasion or wear, blistering, flaking, and even cracks in the wood or coating, but more often growth of mould and blue stain fungi. A field test with claddings was established in southern Norway to study the variation in moisture content in the cladding, the material temperature and the ambient microclimate. The aim of the field test is to provide data that can be used to estimate aesthetic service life of claddings based on material properties, surface treatments, and climate. One of the primary objectives is to identify conditions that are critical for establishment and development of mould and blue stain fungi. The field test will also be used for preference studies in order to identify critical levels of visual changes. Claddings were made of Norway spruce (Picea abies (L.)) from two sites with different growth conditions. It includes both heartwood and sapwood, and both juvenile and mature wood. Selected boards were crosscut into four pieces, of which three were treated with different paints, and one was left untreated. The samples are exposed in an open environment, facing either north or south. Relative humidity and temperature is measured in air close to surfaces, and wood temperature and moisture content are measured in the claddings. Moisture content is calculated by measuring direct current resistance across grain, and corrected for temperature. Mould growth and blue stain fungi, as well as mechanical changes on the surface of the claddings were evaluated visually according to the EN 927-3 standard. Results from the first year are presented. It shows differences in moisture content and material temperatures depending on colour and exposure, whereas the differences in mould growth are minor so far.
G I Vestøl, L Ross Gobakken

Mould growth on spruce claddings and the effect of selected influencing factors after 4 years of outdoor testing
2015 - IRG/WP 15-30671
Norway spruce (Picea abies) is the most frequently chosen wood species as claddings in façades in Norway, and is used both coated and uncoated. The visual changes that occur during weathering can be colour changes, abrasion or wear, blistering, flaking, and even cracks in the wood or coating, but more often growth of mould and blue stain fungi is the main challenge. A field test with synchronous monitoring of relative humidity, air temperature, material temperature and wood moisture content in Norway spruce claddings has been performed in southern Norway as part of the ClimateLife project. Visual evaluation of blue stain and mould growth according to EN 927-3 was performed, and evaluation data after 46 months exposure is presented. The objectives were to study the effect of 1) environment, 2) cardinal direction and 3) colour of the coated surface on growth of blue stain and mould fungi and to study the variation in relative humidity, air temperature, wood moisture content and material temperature. After 46 months exposure, the red coating system had generally the lowest mould ratings and the uncoated claddings had the highest. Of the white coloured claddings the ones facing south had lower mould ratings than those facing north, but the opposite were found for red coloured claddings. The relative humidity was higher in front of claddings exposed northwards and in a shaded environment compared to an open environment against south. In an open environment red coloured claddings had the lowest wood moisture content and highest material temperature, and red coloured claddings against south had the highest maximum material temperature.
L Ross Gobakken, G I Vestøl

Fire protection of wooden facades in Norway
2015 - IRG/WP 15-40710
Wood products are experiencing a renaissance as construction material in Europe due to their environmental benefits. In Norwegian building design however, timber has always played an important role but has had its limitations in urban architecture. One of the reasons is a high demand to fire safety in dense house building and multi-story buildings. Though novel construction methods and fire safety design concepts have widened the field of applications during the last years, architects and engineers still face challenges in using wood in buildings that require high fire safety. A critical point of many flame-retardant chemicals in outdoor applications is their poor fixation in wood; they are prone to migration due to moisture changes, which bears the risk of salt crystallization on product surfaces often associated with damage of coatings. Additionally, loss of the chemicals may decrease the fire performance. The draft standard prEN 16755:2014, superseding TS 15912:2012, prescribes the classification requirements for the durability of the reaction-to-fire performance of flame-retardant-treated wood products in humid conditions. The development of the TS 15912 into a European standard is an important but only a first step forward to guide planners to find suitable flame-retardant treated wood products for outdoor applications. The awarenes’ of building planners and the construction industry for choosing appropriate treatments in humid conditions has to be raised; besides, a further development of flame-retardants is desirable, which show a high leaching resistance and, at best, increase the durability against decay and discoloring fungi.
U Hundhausen, K-C Mahnert

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

Fungal resistance and accelerated weathering of Wood-Plastic composites reinforced with Maritime pine wood flour
2016 - IRG/WP 16-40750
This study evaluates the durability of wood-polymer composites (WPCs) elaborated for use in cladding application from recycled polypropylene (rPP) and wood flour. Local Maritime pine wood flour derived from regional sawmills was used in the study to reduce the environmental impact associated with transport. Different wood-plastic ratios with and without UV stabilizers and biocide were tested. One biocide and two UV stabilizers were tested and their impact on the performances of the elaborated composites was assessed by artificial weathering and fungal decay tests. Results showed that formulation with biocide exhibited low masse losses. Compared with the formulations without UV stabilizers, accelerated weathering resulted in discoloration (E) and slight reduction of the maximum strain, which was enhanced by the addition of 1 wt% UV stabilizers to WPCs formulations. The study showed that the performances of WPCs elaborated from maritime pine wood flour and recycled PP could significantly be improved by using biocide and UV stabilizers.
M Jebrane, T Fournier, N-E El Bounia, F Charrier-El Bouhtoury

Colour changes in unpainted wooden façades – Fifty Shades of Grey
2018 - IRG/WP 18-10903
In Norway the use of weathered unpainted, wooden façades has increased in popularity the last 20 years, both in single family houses as well as in multi-story and non-residential buildings. The benefit of using unpainted wood as façade material can be several: low maintenance costs, low environmental impact and low carbon footprint as well as contemporary and trendy aesthetic appearance. The variation in colour and pattern seen in an unpainted weathered wooden façade tells the story of the chosen design and construction and the loads of the environmental factors the building is exposed to. Usually unpainted façades do not get an even and homogeneously grey façade, but the weathering rather gives a variety of grey and brown tones in the wood. For building owners, architects, building contractors and others, the gradual colour change and patchiness of the wood can be rather surprising and sometimes unwanted. In some building projects, the character of the colour development did not reflect the consumer expectations, and entire façades were exchanged or given a surface treatment after some years even though an unpainted wooden façade can fulfil its function for more than 60 years if correctly executed. It is therefore important to disseminate the information on how an unpainted wooden façade changes its colour over time and how construction details and design options influence this process. The ‘visual guide’, Colour changes of unpainted wooden façades - examples and experiences, has been published as a report in Norwegian as collaboration between the Norwegian Institute of Bioeconomy Research (NIBIO) and The Oslo School of Architecture and Design (AHO) in the course of the Wood Be Better project. The guide is based on building projects from different climatic regions in Norway and the target group of this publication are architects, house owners, building engineers and contractors and others who are interested in exploring the possibility of using unpainted wood in façades. Our main goal is to show through examples of building projects that colour changes on unpainted wooden façades are not random but follow predictable patterns and logic. We want to illustrate some of the requirements and mechanisms of weathering of wood to give a structured overview over features and constructive details in a façade that is followed by colour changes and describe how these details influences the colour of the wooden façades in existing buildings.
K Zimmer, L R Gobakken, O Flindall, M Nygaard

In-service performance of wood claddings and windows – a Norwegian survey
2018 - IRG/WP 18-20632
The overall aim of the study was to strengthen the empirical data on decay frequency and in-service performance of claddings and windows in Norway. Data from a survey of claddings and windows from 38 Norwegian houses is presented. The main findings for wooden claddings: 1) predominance of decay was detected in east facing claddings, while the largest decayed areas were located on south facing claddings, 2) yellow and grey were the most used cladding coating colours and these houses also had most cases of decay damage. Yellow coloured cladding had significantly larger mean decayed areas than grey coloured cladding. The main findings for wooden windows: 1) predominance of decay was found on south facing windows. South facing windows also had significantly larger decay damage areas than east and north facing windows, 2) white and grey were the most frequently used window coating colours. Grey windows had significantly larger mean decay damage areas than white windows. Given the right execution of details and maintenance regime wooden claddings and windows can last for more than 50 years in Norway.
L Ross Gobakken, G Alfredsen

In-line quality control of the film thickness in industrial coating processes for exterior cladding
2018 - IRG/WP 18-40835
The production of industrially coated wood cladding has been strongly increasing in Scandinavia during the last years. In the beginning of this development, industrial coating processes included solely the application of pigmented primers; these however provide only a short protection of the wood surface and the application of a top coat is required during the first 6 to 12 months after mounting the cladding boards. In recent years, the trend has been going to an industrial application of several coats to extend the maintenance interval for repainting. The Norwegian company Gausdal Bruvoll SA is currently starting up Scandinavia’s largest and most modern plant for industrially coated cladding, and aims to implement an advanced process control system that 1) enables automated monitoring and documentation of process and product properties, and 2) provide input data for multivariate analysis and prediction models that will contribute to process and product optimization. The development of this inline quality control system is subject to the ongoing research project KonTre (2017-2019). During the first project year, KonTre’s consortium has mainly worked in laboratory scale to develop, adapt and test appropriate measurement systems for in-line control in Gausdal Bruvoll’s new coating line. The work dealt with non-destructive methods to determine spraying and color failures, coating film thickness, microfoam, wood moisture content, and sub-surface temperature in cladding. The present paper describes the development towards industrial coating application on exterior wood cladding in Scandinavia during the last years and discusses the feasibility of using thermal optics for in-line film thickness measurements.
U Hundhausen, M Slabohm

Enhancing service life performance of oak decking and cladding using organosilicon treatments
2018 - IRG/WP 18-40838
The Life+ project SILEX, in full “Improving sustainability of construction materials using innovative Silicon based treatment” started in April 2013 and was finalized mid 2017. The aim of this project was to demonstrate that a new class of compounds can be used for wood treatment for an extended service life combined with enhanced new testing methodology. Ultimately, it was the intention to demonstrate performance of treatments with silicon-based hydrophobers, which have a lower impact on the environment with a lower input of biocides than conventional wood preservation. This paper provides mainly a descriptive summary of a demonstrator set up including the most promising treatments and having a focus to check long term performance and to allow potential users to check treated items in a benchmarking concept. Although several wood species are included, a fair part of the set-up has been dedicated to treating European oak in relation to cladding and decking applications. European oak has always been considered a local wood species with high potential for long service life in higher use-class applications. Recent discussion related to durability classification based on laboratory assessments has revealed higher variability than when based on long-term experience. As it is expected that there is an impact of moisture dynamics on the service life performance alongside the intrinsic durability based on heartwood components it becomes obvious that methods that contribute to improve moisture dynamics can be considered beneficial. However, oak heartwood has the disadvantage of being refractory to impregnation and hence we focus on dip treatment to achieve potentially high quality products that are not opaque coated and keep the natural looks.
J Van Acker, J Van den Bulcke, J-P Lecomte

Evaluation of the physical properties of heat-treated native Peruvian woods for their application as coverings in buildings located in in arid, semi-warm and humid climates
2022 - IRG/WP 22-40943
Wood is a material that has properties suitable for its use in construction: as a structural component, cladding or decorative element, however, it is necessary to have knowledge of its physical, mechanical and thermal properties in order to have a logical criterion when applying it. It is known that wood has hygroscopic properties, so it tends to absorb the relative humidity of the natural environment where it is used, in this process there is an exchange of humidity between the wood and the air, affecting in an important way the performance of the material. Heat treatment is a procedure that improves the physical properties of wood, decreasing its dimensional variation and absorption coefficient and increasing its resistance to attack by xylophagous fungi and its thermal insulation properties. The present research aims to evaluate the performance of two Peruvian timber species: Cedrelinga catenaeformis Ducke and Matisia Cordata, comparing the performance of both species against humidity to know if it is possible to apply them as building cladding in arid, semi-warm and humid climates of the southern Peruvian coast. The international standard ASTM D4442 (2016) and ISO 15148 (2002) were used as methodology to know the Moisture Content and Absorption Coefficient in both species, both untreated and thermally treated. The results showed that the performance of both woods against humidity was different, where the thermal treatment in Cedrelinga catenaeformis Ducke wood was significantly positive, reducing its absorption capacity and speed by 73 % when thermally treated at 180 °C, while for Matisia Cordata wood the results were not favorable, because its absorption capacity and speed increased by 9 % when thermally treated. It can be concluded from both tests that in real use in humid conditions or prolonged rain, typical of the arid, semi-warm and humid climates of the southern Peruvian coast, Cedrelinga catenaeformis Ducke wood would have a better performance than Matisia Cordata wood, either in its natural state or thermally treated at 180 °C.
K Ayala Castro, A Loayza Argüelles, V J Pilco Mamani