A field test of six millwork preservatives has been ongoing for 25 years, using a "Y-joint" as the test unit. Three preservatives provided excellent protection to white pine and white spruce: 5% pentachlorophenol in varsol, phenyl mercury oleate in varsol, and 0.75% oxine copper in varsol.
This report analyses softwood-drying practices in Canada and identifies the R&D efforts required in this field. These issues need to be examined in order to address environmental concerns and implement solutions that will improve energy efficiency and reduce greenhouse gas emissions.
Developing advanced softwood-drying control systems would reduce energy use and enhance product quality. According to some researchers, the potential reduction in energy use by kilns in Canada would be 5.5 PJ per year, or 335 kT per year in carbon dioxide (CO2) emissions. Furthermore, it is estimated that CO2 emissions could be reduced by an additionnal 90 kT per year through a decrease in the amount of lumber that is downgraded.
This study aims to give an overview of the main trends in developing control systems and to identify barriers to their introduction. It will also serve as a starting point for launching and directing projects on control procedures for lumber-drying in cooperation with the industry, universities, private and public laboratories, manufacturers and users.
In keeping with this objective, researchers for this study surveyed members of the Quebec Lumber Manufacturers' Association and a few mills in British Columbia. The main findings are as follows:
- Industry opinion is that its facilities are sufficiently modern to meet current market needs.
- Industry opinion is that quality (grade reduction / rejection rate) is the most significant factor when evaluationg drying systems.
- Because it is not easy to measure the quality of the drying process, drying time is the most often used to evaluate drying performance.
- Although quality was identified as the main variable in the drying process, the proportion of under-dried and over-dried lumber units was 9 and 16 percent, respectively.
- Operators play a significant role in drying operations (they manage the process before, during and after drying), and their actions affect the results of the process considerably.
- The decision to purchase a drying-control system is driven more by the acquisition of a kiln than by requirements related to the process itself.
The researchers reviewed current technical knowledge of the main dry kiln control systems by considering two types of controls : air temperature control when drying ; and setting up drying programs. The figures in this report illustrate the use of these two approaches along with various other control methods employed in the industry.
There are five softwood kiln controller manufacturers in Canada, which together account for 75 percent of the Canadian market. Although they use similar controllers, there are differences in how drying programs are set up and how changes in moisture content are measured during drying. In spite of recent technological advances, proper drying operations still depend on operator expertise.
R&D on new measurements instruments and mathematical models has not resulted in advanced kiln controllers so far. Innovation in this area has not kept pace with the advances in other leadings sectors. One technical problem that has not been resolved is that of measuring moisture content. In spite of more than 20 years of effort, mathematical models are still being developed in the scientific community, and few applications resulting from this work have benefited the industry other than those supporting operator training.
The research community and the industry acknowledge that the development of an advanced controller represents a promising avenue for improving the lumber-drying process. Unfortunately, problems in modelling the drying process and measuring moisture content remain represent major obstacles to the development of high-efficiency controllers.
Another obstacle relates to the difficulty of evaluating the financial benefits that would accrue from potential advances with the necessary speed and accuracy. These, then, are the key factors hindering the introduction of new drying technologies. They also explain why length of drying time is still the most frequently used control variable, despite the fact that the industry considers finished product quality more important. Furthermore, it appears that operators' actions significantly affect what happens not only in the kiln but at all stages in the process, from sawmill to shipping.
In view of this, we believe that a system for monitoring the entire drying process is worth investigating. Such a system would :
- serve to collect all data generated by measuring instruments at all stages in the process, from the sawmill to the planing mill
- help to establish productivity and quality indicators for measuring the monetary value of process enhancements introduced by operators
- make it possible to provide a rationale for other promising research approaches such as multivariate analysis and experimental design
This approach would make it possible to enhance control of the drying process and process quality while also revealing potential energy savings.
With the pressures on our industry at this time, sawmills are using thinner saws to try and improve recovery without reducing current production levels. This has led to washboarding becoming a widespread problem in the industry. Washboarding is a wavy pattern that appears on the surface of lumber due to excessive vibration of the sawblade as it cuts through the lumber. In this study the washboarding behaviour of saws was studied at both the analytical and experimental levels to develop a much better understanding of the problem and lead to a set of guidelines for industry use.
This was a joint project between Forintek Canada Corp. and The University of British Columbia. Dr. S. G. Hutton led the analytical side of the work and Dr. J. Taylor the experimental portion of the work. This report is a portion of the overall research endeavour and presents the results of the experimental work that was conducted.
To compliment and validate the analytical portion of the work a series of cutting tests were conducted to examine the washboarding phenomenon and the factors that influence its occurrence. The effects of wheel rotation speed, strain, tooth bite, and depth of cut were examined and their effects recorded. As small changes in tooth design are known to influence a saws washboarding behaviour, but are not accurately predicted by the mathematical models, we also carried out cutting tests with saws of different thickness and tooth pitch, progressively increasing the length of the tooth face and the depth of the gullet until washboarding on the lumber surface was quite severe. In this manner we hoped to be able to develop some guidelines for the industry.
It was apparent from the initial tests that there were two types of washboarding. We have called the larger diagonal waves that often appear with industrial sized bandsaws, Type I. The narrow more vertical pattern or that on circular saws is called Type II. The results in this report are primarily associated with Type I and show the somewhat insensitive nature of the washboarding instability to changes in the operating parameters. The occurrence of washboarding is more sensitive to changes in the tooth geometry.
Industrial heat treatment technology for wood has been under development since the 1970s. The technology consists in heating wood to temperatures of from 150°C to 240°C while preventing it from burning. This is achieved by heating the wood in either an inert atmosphere or saturated vapour environment. Heating the wood over 200°C changes the chemical structure of the wood and results in a reduction in its hydrophilic behaviour. After heat treatment when wood colour has changed to brown, an improvement in dimensional stability and biological durability should be observed. However, some mechanical properties of the wood may have decreased. This enhanced dimensional stability and biological durability make heat treatment an interesting option for the protection of wood used in exterior applications. The objectives of this study are to assess the performance of heat treatment technologies and to determine the properties of jack pine and balsam fir after heat treatment, as regards to exterior applications. Owing to difficulties in the start-up period that significantly delayed the project, no experimental work had been conducted by the end of March 2003. The lumber has however been sent to two companies for treatment and the physical and mechanical tests will be conducted under a new project entitled “Quality Control and Certification of Thermally Modified Wood.” A final report will be issued at the end of March 2004.
Engineered wood flooring (EWF) is gaining in popularity since it appeared in Europe in the 70’s. 40% of the wood flooring installed in the USA is EWF and 75% are EWF in Europe. In layered wood composites such as engineered wood flooring, dimensional stability is of primary importance. The non-homogeneous adsorption or desorption of moisture by the composite may induce cupping, thus decreasing product value. These products were developed by the industry with the result that knowledge on the product and its behaviour is very limited. The objective of this study is to develop a finite element model of the hygromechanical cupping induced by moisture desorption in layered wood composites. The model is based on two sets of equations, 1) the three-dimensional equation of unsteady state moisture diffusion, and 2) the three-dimensional equations of elasticity including an orthotropic Hooke’s law, which takes into account the shrinkage, and swelling of each layer. The model was used to assess 34 different constructions. Results may be used as guideline in the design of new engineered wood flooring construction.
China has long been recognised as a major potential market for wood-based products. This view has been fuelled by the scale of the domestic market, rising GDP per capita (albeit from a low base), a demonstrated government commitment to housing reform, reduced timber supplies and, more recently, China's accession to the World Trade Organisation (WTO).
These enormous market changes will have significant implications for forest products exporters. A cursory examination of the literature suggests that while there is considerable information and analysis of past trends, few of these provide comprehensive clues to the real areas of competitive advantage for softwood producers, or provide insights into the demands of future Chinese wood products consumers, who will undisputedly be of a different genre to the past consumer.
This study investigates these potential opportunities via a two-part literature review and the results of a market benchmarking survey of almost 1,000 existing or pending homeowners in Beijing, Nanjing and Shanghai, three cities which have been identified with the largest potential for increased demand for wood products related to housing. The first of the literature reviews focuses on the published demographics of housing demand in China, and serves as a background to the benchmarking survey results. The second review is a paper written by Dr. David Cohen at the University of British Columbia, and investigates the cultural, political and societal changes and its impacts on foreigners doing business in China. The benchmarking survey was intended to record the existing awareness of wood-frame residential buildings, along with positive and negative attributes that they associate with these structures.
Highlights of this study include:
At over 1.2 billion people, exploding urbanization, steady economic growth and a significant housing deficit, the growth in demand for housing materials/systems will be massive over the coming decades. At the same time, government reform has created a housing market where consumer quality demands exceed what was previously offered by the State.
With continued environmental protection policies, self-sufficiency in building materials will continue to decline, relying more and more on imports. (Note: overall imports surged by 63.4% year on year in January of 2003, to US$31billion; exports grew by 37.3% to US$29.8 billion, leaving China with its first monthly trade deficit since December 1996. [The Economist])
Like Japan, China’s population is aging, largely due to their “one child” policy. The number of people aged 60 and over is predicted to double in size by 2020.
Income distribution in China is uneven geographically and the disparity is widening. 2.2% of the population of China, living in such cities as Shanghai and Beijing, had reported annual household incomes between US$10,000 and US$15,000 in 2001 (CPIRC). This is considered a very affluent income level in China, a point that must be kept in mind regarding the population’s ability to pay for B.C./Canadian wood products. In contrast, over 50% of the population in China live in western and inland parts of China and earning less that US$1,800 in 2001.
These income levels were confirmed in the market benchmarking analysis of this study, showing annual household incomes among the respondents of primarily between CDN$4,600 and CDN$8,900 per year (26,000 to 50,000 RMB). It should be noted that the vast majority of these household incomes are earned by two people, meaning the average income per person is half this.
Further, average monthly rents for those that did not yet own their homes was CDN$191 for Beijing, CDN$122 for Nanjing and CDN$143 for Shanghai for those surveyed. Surprisingly though, the average existing/expected home purchase size (primarily apartments) was 97 m2 at a price of CDN$72,000 for Beijing, 125 m2 at a price of CDN$75,000 for Nanjing, and 109 m2 at a price of CDN$83,000 for Shanghai. There are two explanations for this divergence between income levels and willingness to pay for housing. First, savings rate is very high in China as compared to Canada. Second, not unlike Japan, interest rates are very low. It will be interesting to see what the existing levels of bad debts in China’s banking system does to the latter in the coming years.
Although evolving, China’s cultural, political, social and economic realities necessitate that B.C./Canadian exporters understand the environment to succeed. The need for local joint ventures, an assessment of risks/costs/benefits and a clear understanding of the dynamics of this market are critical.
The awareness of North American platform-frame and Japanese post & beam wood building systems was significant in all three cities investigated. For example, 44% of the respondents in Nanjing were aware of Japanese post & beam and 22% aware of North American platform-frame homes. Awareness came primarily from advertisements in China, followed by exposure through television / cinema programming. Awareness of wood-based home systems increased both with the respondent’s level of income and education.
There was an even higher awareness of combined wood / concrete / masonry building systems. This was found as a curious result as evidence of such structures in urban China is not evident. Further investigation revealed that the high awareness comes from the respondents’ previous life in (or knowledge of) rural homes in China where such structures are common. This is a very important issue regarding the Chinese connotations of wood-based homes. The image of these masonry/wood rural homes is not high, but rather associated with subsistence living. This is a much needed area for further market research, as it will not be clear whether or not this influences responses to positive / negative attitudes toward wood-based homes (next two highlights).
Aesthetics of wood-framed homes was the number one positive attribute in the survey in all three cities, followed by its insulative properties and environmental protection. Attributes such as “natural” and comfortable were also common among respondents. It is interesting to see that the performance of wood structures was NOT listed as a positive except for its earthquake resistance (see negative attributes).
On the negative attributes side, concerns over fire ranked number one in all three cities. The other negative attributes noted were virtually all performance related, including lack of insect resistance, moisture resistance, or even seismic concerns (conflicting with the positive mention above). Dealing with the concern over these negatives will be key in any promotion activity in China.
The results of this study suggest that there is a strong potential demand B.C./Canadian wood products/systems. In addition to continuing exposure through the existing promotion of high-end single-family homes, it is recommended that the greatest potential lie in the recognition of the cultural, social, political and economic realities that exist for housing in China. These largely point toward increased wood-use in their common low-rise multi-family structures. This must include dealing with the existing negative performance connotations of wood by the Chinese.
Promotional efforts by our government and industry need to incorporate the knowledge gained by the market intelligence generated in this and ongoing market research studies.
Exposée à la chaleur élevée, la structure chimique du bois se modifie. Des recherches sont en cours depuis plusieurs années quant à l’impact de ces changements sur les propriétés physiques et mécaniques du bois. Différentes technologies de modification thermique ont été développées et plusieurs brevets ont été octroyés à ce sujet. Le bois thermiquement modifié commence à prendre sa place sur les marchés européens, et ce qui suit vise à répondre aux questions les plus fréquentes concernant la technologie et le produit résultant de la modification thermique du bois.