The Sustainability Of Prefabricated Wooden Components

Introduction

Using wood in building structures is nothing new, wood it has been used as a building material throughout the ages wherever forests grow. And today, the international timber trade provides countries which do not have extensive forest resources with wood from sustainable and certified forestry to help them build. Building with wood is becoming increasingly popular as countries around the world seek more sustainable construction; already 70 percent of the housing constructed in the developed world use wood frame. Although steel, plastic or metals are more common construction materials, now the constructers are looking at different solutions, like wood. Like Harvin Green says “ ordinary people assume that they know or can readily discover how to work with wood, whereas working with metal and plastic is mysterious, dangerous or requires tools that are too expensive and too large for most people to acquire or use . Metal is hard, difficult to cut when cold, and can be sharp enough to seriously wound a person. Most metals require great heat before they can be manipulated, and metalworking (other than jewelry making) is associated with soot, the heat of the forge, and muscular smith sweating at the anvil. Plastic is more easy malleable, but they can give off toxic fumes when heated, as well as benign odors that merely smells dangerous.” (Green 2007, page 4). Reading this paragraph it is clear why wood is a better material for any building structure. Wood has many benefits as a building material:

It is naturally beautiful and widely available.

Its low thermal resistance and capacity to insulate provide excellent energy-efficiency.

Strong and light, with exceptional load-bearing capacity, it is easy to handle and transport. It reduces the need for massive foundations.

Fast, flexible and simple to renovate, it is easy to work with on-site using simple tools, yet ideally suited to factory pre-fabrication.

It is available as solid wood lumber products, graded to meet performance requirements, or can be engineered into panels, columns and beams manufactured to meet precise performance characteristics.

Above all, it is a naturally renewable, organic material that makes a significant contribution to the reduction of the earth’s emissions of carbon dioxide.

Despite all the good things about wood, there are also some that make it less effective and even unusable in some situations. The most important negative things of wood could be:

It doesn’t absorb nor store the solar heat.

Being an organic material, it has some natural enemies like thermites and fungi.

It cannot be used efficiently in high moisture environments.

It can burn very fast.

1.2 Problem statement/hypothesis

These are the questions that I want to answer in my work “The sustainability of prefabricated wooden components”:

Why are steel and mineral based building components still the predominant base for construction industry when wood is a more sustainable building material?

Is it more sustainable than steel construction or mineral based building component?

How about the energy that you invest for using the prefabricated wooden components?

These questions exist because of the implementation of sustainable development strategies in the processes of industrialization of wood.

1.3 Method

The subjects that I will talk about in my work “Sustainability of prefabricated wood components” are the advantages and the disadvantages of using the wood as a material for constructions. I will as well talk about the concept of sustainability, defining the concept and giving examples of situation where wood was a sustainable resource.

Between assumptions and results, organizing, conducting and completing a study or research require the use of methods which contribute to ensuring the objectivity of the entire activity. For studying my theme I choose to study the bibliographic materials. In any study or research is absolutely necessary to use specialized study of works whose content is related in some degree to the topic under study.

1.4 Target group

The target group of my work “The sustainability of prefabricated wooden components” are the builders, especially, and not those who are using the components. I will guide my direction to the euro builders in general because they have to know the problems that any raw material have or if there is any danger in using it. I will also talk in my work about strategies that any builder has to know in order to make a sustainable wood component. So, reading my work “The sustainability of prefabricated wooden components” any builder will know if the wood is the perfect material for his construction.

1.5 Scope of my thesis

I don’t want to insist on the problems created in the ecosystem because of using wood as a construction material. I will only resume at the builders’ problems and how can it be solved. In the second chapter of my work I will present the theoretical elements, the physical, mechanical and thermal characteristics of wood, which are the factors that deteriorate this material and how those factors can be removed. Also in the theoretical part I will define the concept of the sustainability and how this concept is applied in industrial activities. In the theoretical part I will answer at the question: does this material deserve all the investments of a builder? And if the answer is yes, what are the factors that make wood a sustainable material? In the practice orientation chapter I will give examples that admit that the answers I found in my second chapter are true. I will also find a connection between practice and theory establishing what part of theory doesn’t fit in the practice part, or to be more precise, what theories aren’t applied in practice.

So, the scope of my thesis is to answer the questions that stated above and to conclude whether wood is indeed a sustainable material or not.

Chapter II Theory

2.1 General characteristic of wood

Wood can be considered the first building material ever. From prehistory to the present day this material was used consistently in the most varied ways. Harvey Green says that “for millennia wood has been a familiar and ordinary substance, common in people’s lives, used for heat, shelter, food preparation, light, weapons, tools, toys, storage, land and sea vehicles, decoration and design. It is in fact so familiar that we often dismiss it as a “common” substance-even as we spend money replicating it artificially-and yet its use and appearance send a strong signal of class, status, authenticity or something less tangible or definable” (Green 2007). This is due to the spread of wood in the form of various species in the whole world and its workability, its low weight and good mechanical properties.

Most important characteristics of wood can be classified into three categories:

A. Physical characteristics

B. Thermal characteristics;

C. Mechanical properties and deformation.

Physical characteristics

A.1. Humidity

Moisture content is a very important characteristic affecting all physical, mechanical and technological properties of wood and wood-derived products. Moisture variation also leads to changes in the dimensions of limitations. In constructions, to avoid negative phenomena caused by high shrinkage deformations, the wood and wood products have to be used with humidity as low as possible.

A.2. Density

Wood, by its structure, is a material more or less porous, but the actual density of wood substance is 1.55 g/cm3 and is the same for all the essentials. The density is one of the important characteristics of wood because all the physical, mechanical and technological properties of wood are conditioned on its value.

A.3. Shrinkage and swelling

The shrinkage and swelling means changing the dimensions of wood under the influence of variation in moisture. Variations in shrinkage in relation to humidity may cause, during drying, besides changes in size and torsion phenomena, deformation and cracking of wood products that may affect product quality and durability. Shrinkage and swelling phenomena can also create difficulties for joining wood elements leading to the partial loss of the mechanical strength of the assembly. In such situations it is recommended that joints are constructed so as to allow periodic adjustments to ensure the best connection.

B. Thermal Characteristics

The use of wood and wood based construction depends on favorable thermal properties. And in the same time thermal conductivity depends on the density and moisture content of wood. So, it is very difficult to say whether a characteristic is more important than another. We have to consider all the characteristics in order to make sure that wood is a durable resource. Like the others materials, wooden parts or components change their dimensions proportional to temperature variation.

C. Mechanical properties and deformation

Mechanical properties of wood depend on a number of factors, among which the most important are: the type of load, the load to the fiber, duration of maintenance, cost of maintenance, structure and defects of wood species, moisture. Although it is an ideal raw material for industry, wood is a natural resource, the resource to be protected as much as possible to avoid unwanted social and environmental effects.

Functional properties of wood, its different uses and the population growth keep the demand of this material at high levels even in the future. Wood is designed to be mechanically or chemically processed, or used in construction or as fuel. From medieval times until now wood allowed the development of energy-intensive industries that require high temperatures, such as steel and glassware. Given the multiple uses, actions are required to make wood a sustainable resource. The companies that are using wood as construction material have two main reasons to make it a sustainable product: the first reason is that any company wants to offer good services for their clients. So they have to build a sustainable product out of wood because they are or want to be a brand. The second reason refers to the ecosystem. We all know that wood is a natural resource and if the builders are turning it into an unsustainable product it means that this resource is going to be more and more used for creating unsustainable products, so the next question is: If we are using wood and we don’t worship this resource, what kind of materials will our children use? I asked this question for noticing the importance of this resource. I will mention all uses of wood and then I will develop the research of using wood as a construction material.

Because of the qualities and properties, wood has many uses, the most important being:

• Construction (houses, beams, columns, wall panel construction, manufacture of parts of traditional and modern wood joints, railway sleepers, wood studs, plywood, chipboard, hardboards, flooring/ceilings and their supporting structures).

• Combustible material;

• Timber industry, where wood is the raw material;

Timber industry, one of the branches of the woodworking industry, use of annual quota over 65% of coniferous and over 35% of the hardwood.

• Obtaining charcoal carbonization process consisting of wood;

• Light industry (paper, pencils, toys);

• Using waste wood recovery in various fields and activities (agriculture, poultry, domestic purposes);

• Heating (mostly in rural areas).

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Dietrich Fengel and Gerd Wegener say that the chemical composition of wood and the factors that that builder has to consider when he uses wood as construction material are the macromolecular substances (cellulose, polyoses, lignin) and the low molecular weight substances (those contribute only a few percent to the wood mass, but they have a great influence on the properties and processing qualities of wood).

By its basic components (cellulose, lignin and extractive substances) wood has other uses:

• Getting technical cellulose for industry, by scaling the wood;

• Lignin is a potential source of phenolic products of organic synthesis industry. It may also have uses in the rubber industry. The lignin resulted from wood scarification process may be used for developing insulating materials. Lignin can also be a good fuel due to its high carbon content. This gives a high caloric value which in the composition of the by-products, bark or sawdust, becomes a readily biodegradable pollutant.

2.2 The concept of sustainable development in industrial activities

The roots of the concept of sustainable development are in promoting sustainable use of natural resources. International organizations aim at conservation of marine resources, of wildlife, protection of cultural and natural heritage. Their actions focus on protecting the global environment and indicate a wide international acceptance of sustainable use of natural resources.

The concept of sustainable development has set the objective of generally accepted human ecological footprint by promoting environmental integrity, equity between nations, individuals and generations and maintain economic efficiency.

The concept of sustainable development has the following definition: "Sustainable development is the type of development that aims to meet the needs of the present generation without compromising the ability of future generations to meet their own needs." This definition takes us more to the natural part. First thing that comes to readers mind when reading this definition is that the wood is an important resource and must be used wisely in order to preserve it. But I chose this definition because the builders have to know why they have to build a sustainable product for their clients; to show that in an example, if a carpenter manufactures a piece of furniture out of wood for a father, he must make sure that that piece of furniture is going to be used by his son too.

Sustainable development aims to find a stable theoretical framework for decision making in any situation in which a man / environment relation arises, be it environmental, economic or social one.

Although sustainable development was initially meant to be a solution to the ecological crisis caused by intense industrial exploitation of resources and environmental degradation, looking primarily at preserving environmental quality, now the concept extended to the quality of life in its complexity, both in economic and social terms.

Gradually, the concept has changed its content and meaning through various derivative concepts such as “sustainable growth”, “sustainable use”, “sustainable consumption” or “lasting partnership” or “environmentally friendly practices”.

The industries which use natural resources must initiate long-term strategies that meet the tolerances of nature and based on the precautionary principle learned at individual and institutional level. Therefore, the following strategies and their implementation should be considered:

Establish indicators to tell the situation of a component or another, a field or another, to one industry or another;

Develop processes, methods of definition, expression and measurement of such indicators;

Promoting normative instructions, methodologies for assessing the level of these indicators in relation to acceptable, recommended limits or the best experience in the field;

Attempts to develop models for the selection of indicators in order to specify the significant ones, the main ones, important at small scale or at macro level, the best technologies and the best environmental practices that best meet social expectations;

Attempts to develop models of use of the indicators listed above, a set of synthetic indicators, providing a unified vision, integrated and reflecting the balance of society development;

Prioritizing on certain scales of the situation of different countries, regions, industries, and the prevailing trends,

However, these strategies must take into account the determinant factors that make it necessary to impose these strategies:

• The economic factor as the motor of society;

• Environmental factors as the item to bear the consequences of uncontrolled development, chaotic, with effects potentially irreparable, the environment and, in many cases or areas already manifested;

• The human factor, the human being, however, "the measure of all things";

• Technologic factors, the element that ensures the development, but tolerable limits for resources, the environment, human health and biodiversity.

The relevance of the relationship between economic prosperity and environmental security is confirmed by the coupling of energy consumption to economic growth. Traditionally, growth of economic activity implies increased consumption of energy and materials, which in turn increases environmental degradation. So, this is the reason I spoke about the sustainable as a concept that refers more at the natural subject; for observing the connection between the human factor and the natural factor. Like I said in the previous chapters, the manufacturers have to make a sustainable product from wood for having economic development on one side but on another side, they have to be careful because wood is a exhaustible resource.

For economic development, builders have to offer products that have to:

1). Satisfy a need, a utility or a well-defined purpose

2). Meet customer expectations

3). Conform to standards and specifications

4). Comply with legal and other requirements of society

5). Be available at a competitive price

6). Be provided at a cost which brings profit

So, those are the conditions that wood products have to accomplish for being perfect for a customer. When one says “to meet the customer expectations” and “conform to standards and specifications” he includes here the idea that wood has to be a sustainable material and has to be made to resist. The sustainability is a problem for the builder and for the customer too. The difference between them is that the builder has to find solutions to resolve this problem while the customer only sees the final product making sure if sustainability exists or not.

Sustainable development is a new path of development which covers the needs of the present without compromising the ability of future generations to meet them at least the same extent. This requires a model of economic growth and human activity that takes into account the principle of allocation and use of resources to ensure progressive consolidation of rational development. It must therefore take into account the assessment of natural resources, the cost – benefit analysis of the prices right. So far, the logic of classical economic strategy, environment and natural resources were considered as mere tools that serve growth. Over the passage of time, it was necessary to design and implement such an economic environment, through its inputs and outputs to be in a dynamic compatibility, direct the natural environment and the needs and interests of present and future generations coexist and succeed.

Sustainable and viable economic development is a type or form of economic development that ensures the consumer's satisfaction without compromising or prejudicing those of future generations, which blends harmoniously balanced achievement of economic growth, environmental protection, social justice and democracy.

In general, sustainable coordinates relate to the following dimensions:

a) natural size, which implies a new attitude towards the environment (sustainable development exist only as long as man-made environment is compatible with the natural environment);

b) human social dimension (all outputs from man-made environment must respond directly to the needs and interests of present and future generations coexist and succeed);

c) a national scale – state, regional and global (in the compatibility criteria optimization, both at national and at regional, continental and global).

In the current period, the transition to sustainable development marks mankind was entering the environment in which development risks have increasingly diminished or even removed. The new concept of sustainable development of mankind recognizes the limited resources and, therefore, current models of resource use should be reconsidered. It involves a fair assessment of available funds in each country and adapting institutional and legislative framework to support these programs. If one accepts the assumption that the parameters of performance and environmental quality are likely to become the determining international jurisdiction of the next century, the imposition of environmental criteria in shaping economic development model can be a factor in reducing disparities between different countries and regions.

The absence of such a criterion in the developing countries, an additional obstacle beyond hope, is a serious threat to the future of this country, which is likely to be in the position of being unable to adapt to the new requirements of competitiveness and sustainability processes development. Environmental strategy also aims ultimately to induce structural changes in the economy, so that record size development pressures on natural resources and the environment.

It is necessary therefore that the transition to be oriented to a sustainable development economy, capable in its performance to withstand all pressures and restrictions present and especially future, including those concerning the environment and conservation of natural resources are among the most severe. Hence the need to strengthen the positive links between development and the environment and breaking the negative links between economic growth and environmental damage. This does not stop growth or disrupting the operation of the economic system. It means shifting the emphasis from quantity to quality with all the positive effects that result.

At the same time, sustainable development correlate and subsumes the economic and human development. It can thus be appreciated that development must have in its center the human being in all its dimensions rational, moral and spiritual, of both sexes, at all ages, from birth to old age. It must be the core, everything has to leave her and return to her. The concept involves the use of all the faculties and inclinations so that each human has a duty to take the initiative and participate, everyone's responsibility to his family, to the society in which he lives.

There can’t be individual progress unless the society is moving towards better as a whole, through a permanent creativity if individuals composing it does not take any role in it. Like human development, sustainable development emphasizes, first, that development is made for people and involves people in obtaining economic outcomes and achieving equitable income. The second feature of human development reveals that the economic development of social – is carried out by people. The human potential must be created and capitalized on the investment in man, namely in education, culture and education, training and health. Equitable distribution of income and investment in human and material creates the socio – cultural average life expectancy, so that longevity and ability of individuals to live a long and healthy life is the third fundamental feature of human development. Development by people and for people highlights the fourth dimension of human development, which is reflected in the features and opportunities that people have to participate in social life, to be its protagonists.

Also, sustainable human development is simultaneously national and international. Comprehensive vision of human development is another feature of the concept of sustainable human development.

Turning our attention to the creation of a new society, a society of people for people, we can deduce that human development coupled with sustainable development, it is as a general concept. The ultimate goal of any activity should be human happiness, happiness is a noble goal, as versatile as the human species.

In the past, development was designed only from an economic perspective, neglecting that behind growth effort were people who had to live.

New development projects should primarily facilitate the improvement of life for all people, for the masses and not for a elite composed of a privileged few. Otherwise, this is a foreign elite who no longer enjoys the confidence of our citizens and therefore not catalyze the evolution of society to which they once belonged.

We thus estimate that the minimum requirements for achieving sustainable development include:

• resizing growth, given a fairer distribution of resources and improve product quality;

• eliminating poverty conditions meet essential needs for jobs, food, energy, water, housing and health;

• ensuring an acceptable level of population growth;

• forms of government decentralization, increased participation in decision-making and coordination of decisions on the environment and the economy.

     Therefore, sustainable development models should seek to protect the biosphere, the most efficient use of material and human capital, promoting equity:

• protecting the biosphere refers to preventing deterioration of the ozone layer, to maintain the reproductive capacity of natural resources (forests, soil, water) and maintain their quality within acceptable limits;

• efficient use of physical and human capital is measured by transformation yields achieved, for it is necessary to choose technologies on environment (it is assessed by the quality of waste discharged into the environment);

• equity refers to fair distribution of the costs of environmental protection among different categories of economic, population segments, among different countries, it refers to the generations because the quality of the environment, resource management, waste accumulation, concern equally not only present generations and those to come.

In our era, temperatures are rising, the 20 century was the warmest century in the past thousand years and the ten warmest years on record have all occurred since 1990. Rainfall paterris are changing, sea levels are rising, glaciers are retreating and arctic sea-ice is thinning. Without an action to reduce the greenhouse emissions, global temperatures are expected to rise between 1.5 and 6 degrees centigrade by 2100 and the sea level could rise by between 1 and 2 metres.

So, there is a problem and it has to be also a solution. The scientists and the ingineers thought that they have to build a machine that has to absorb the carbon from the atmosphere. This machine it would have to be environment friendly, efficient, reliable, easy and cheap to produce. With other words it has to be a sustainable product. All the scientists and ingineers came up with a solution for this problem: threes and forests.

Threes absorb the carbon from the atmosphere during their growth. The mature forests doesn’t absorb carbon anymore, but they are a carbon reservoir. But if the threes are destroyed they release carbon back in the atmosphere.

8000 years ago half of the world’s surface was covered with forests. Now less than 30% is covered with forests. Between 1990 and 2005 13 milions hectars were lost every day. Tropical countries are most vulnerable. South America, for example, suffered the largest lost of forests from 2000 to 2005 about 4.3 milions hectars every year.

The forest sector can make a difference in helping to reverse the situation. Our contribution on climate changing can come on three main ways:

By conserving and managing the existing forests. We can protect and maintain the carbon already locked up in there

By planting new forests and establishing those we have lost so we can restore the balance of the forest cover

Another thing we can do is to use more wood on our day life. Wood is a source of bio-energy and he can replace the fuel, for example, and avoid the emissions. Wood is also, like I said in the previous chapters, a raw material. Producing wood take less gas that producing any other building material. And the wood stores carbon as long as the building and furniture remains.

Designing future buildings to use more wood instead of concrete, plastic and steal could result in a major drop in gas emissions.

Wood products are unique. They come from a natural sustainable resource, the carbon they contain remains stored for the duration of the product life time. So the global increase in the use of industrial wood products would help reduce the among of CO2 from the atmosphere.

From the above, we believe that the general objective of developing sustainable is to find an optimum interaction between the four systems – economic, human, technological, environmental – in a flexible and dynamic process.

2.2.1.Economic potential

The aim of any economic activity is to satisfy the needs and human needs. In achieving these goals, people start to their interests. From this point of view component of the mechanism of economic activity is the economic interests which are a form of needs economic social. They are an expression of mutual relations between economic agents.

Viewed as a whole and their interdependence, economic interests form a complex and dynamic system. It consists of personal (the individual) and collective (group) general (society), public and private, current and future, periodicals, incidental liabilities (unless accompanied by action) and active (coupled action), regional and national etc.

Human behavior as a relationship between ideals and scarce resources which have many uses, is studied by the economic science. As John Kenneth Galbraith said: "As long as it believes that the economic system works, ultimately, in the interest of the individual – that is subordinated to the needs and desires – it can be assumed that the role of economics is to explain the process by which the individual is served ".( Kenneth , 2001)

Economic potential consists of all material and human elements, useful and valued in conditions determined by the quantity, quality, time and space. The analysis of economic potential requires analysis of its two components: the natural, ecological concerns materials and natural resources human potential. For growth and development of sustainable development is necessary to develop programs or economic development plans. Adjusting the economic mechanism through rational decisions that do not affect the normal operation of the market economy is achieved by planning, respectively by conducting business on a plan.

The plan is a document which included indicators that economic growth tends to reach a certain period of time, as the measures necessary for this purpose, taking into account the material and financial possibilities available to the national economy as a whole and agencies companies. We can mention that planning refers to the overall objectives of development, coupled with the economic agents that not only discouraging them, but could be an advantage.

A proof that wood used as an industrial material is an economic process that has a lot of benefits is the Taasinge company. Taasinge is the oldest and biggest producer of ptefabricated wooden components. This company started his activity in 1971 so she influenced the development of using wood as an industrial material.

According to the new forms of cooperation, Taasinge appeared in many projects with the purpose to simplify the building process.

The prefabricated Taasinge are used usually when:

When the façade has to be replaced

When the façade has to be refurbished

When the roof has to be replaced

For building industrial buildings like a gym, for example, Taasinge adapted to the new energy requires.

2.2.2.Social potential

In a market economy, goods and services are produced for consumption. However, they are divided by economic and social criteria. As a result, goods and services for personal consumption will recover unevenly in society because they have revenues are, in turn, uneven.

In economic literature there have been several ways to explain the inequality in terms of economic and social criteria – political: from theory JB Say's Trinitarian in Marxist or socialist – utopian to fatalistic views. Currently try to explain the differences between rich and poor in a number of economic arguments such as inequality in income, wealth inheritance, tilting towards savings, talent and luck in business, etc.

2.3 The quality of wood as industrial product and its problems

In the previous chapter I talked about the sustainability and its economic development as a consequence for making sustainable products. When I say that a product has to be sustainable I mean that that product has to be a quality one. Quality includes sustainability and other factors that are required by customers and has to be accomplished by builder.

The quality is an important issue for the manufacturer and they will never accept compromise in quality profiles for any deviation from quality standards required by the market requirements because this might have the immediate effect of reducing the number of customers. And producers who think the cooperation with external contractor because of their inefficiency rolled production lines must be convinced that the profiles provided by the contractor are at least equal quality to those produced by them. If the call to an external contractor was made because of the inability to reach a satisfactory quality of profiles made ​​by the manufacturer of doors and windows, quality profiles provided by external contractor becomes a critical factor.

Literature provides a considerable number of definitions of the concept of quality. According to some specialists, product quality is considered a necessity satisfaction, degree of consumer satisfaction, compliance with specifications, assembly means for achieving a viable product, a lower cost for a given use.

In practice, defining quality is made using a number of terms such as:

-Quality of the project (conception quality) represents the measure that the designed product ensures satisfaction and beneficiaries can use, to manufacture that product, technological processes rational and economically optimal.

-Built quality means the degree of conformity with the technical documentation of the product. This is done in production and is determined by the technological process of production equipment, monitoring and control activities, labor, etc.

– Delivered quality, representing the actual level of quality of products delivered by the supplier.

As the industrial production developed and diversification of production growth, product quality concept has evolved and diversified, so now we are talking about:

– "Potential capacity", represents the product quality by design, before assimilation in manufacturing.

– "Partial quality", represents the relation between achieved and the required quality;

– "Quality made", resulting from the quality check at the end of the production line.

– "Assured quality", quality resulting on a single program including all quality control activities (prevention, measurement and corrective action)

– "Total quality" quality which integrates the usefulness, efficiency, aesthetics, etc.

Quality is the set of properties and characteristics of a product or service it gives to the ownership to meet the needs expressed or implied.

Quantitative assessment of quality involves, first, identifying all the characteristics of a product and then the formation of typological groups according to various criteria.

1. In relation with nature and the effect it has on the use, quality characteristics are grouped into the following types:

a). Specifications

Specifications refer to attributes of general product value which gives it the potential utility of consumer satisfaction. This general product value can be in physical, chemical, biological and inner material structure determined by the conception of the product. Technical characteristics are directly or indirectly measurable objectively with sufficient accuracy by technical means.

b). psycho-sensory features

These features aimed aesthetic effects which products have on their users through form, color, taste and degree of comfort. Manufacturers must constantly bear in mind that these features shows great variability in time and space.

c). Availability features

These features reflect the products ability to realize useful functions throughout the life span, skill defined by two fundamental concepts: reliability and maintainability.

Reliability reflects the ability of a product to perform its functions without interruption due to fault in a specified time period and in a given system conditions of use.

Probability in nature as maintainability and reliability measures the chance that a product is used again in a specified period of time, maintained and repaired in existing conditions. It is expressed by a number of indicators such as production cost, price, costs, efficiency and degree of recovery of raw materials. In case of laminated wooden profiles the reliability must be very high for this type of product is the product category that cannot be subject to repair. If there is a substantial probability that the profile will not be able to last the entire lifetime of the window it means that the entire system of quality control activity was completely unsatisfactory.

d). general social features

Those features aim the effects that technological process of products manufacturing has. In Romania manufacturers still do not pay great attention to the social aspect, but for a company that wants to stay on the market on long-term its strategy must include quality and this. For example reducing wood consumption in the production process of lamellar profiles leads not only to reduce costs but also to a positive impact on the environment by reducing deforestation indirectly.

2) Judging by importance in ensuring the utility and functionality of products, quality features are grouped as following:

a).basic features (absolutely necessary). For glulam wood basic characteristics are kind of wood, wood texture quality and the type of adhesive used.

b). secondary characteristics that may be missing or may be made at lower levels, thereby reducing unnecessary costs without the usefulness of the products to be significantly affected.

3) Depending on the destination and type of use in the consumer products, characteristics can be grouped as follows:

a). Characteristics of labor means

-Durability, weight, specific consumption, temperature, precision work, aesthetics, not applicable for glulam wood.

b). Characteristics of work objects

-Ease and efficiency of its processing, finished product quality assurance requirements, consistent chemical composition.

c). Features for individual consumption items

-Taste, shape, tear and abrasion resistance and elasticity, applicable to glulam wood.

4). By measuring or determining, the quality characteristics are:

a). directly measurable characteristics (mass profile, its density, shape, etc.).

b). features that can be measured indirectly (reliability of a profile determined based on the evidence of resistance to wear)

c). features that can be compared objectively by standard samples (number of defects per 1 m profile)

d). features comparable subjectively by standard samples (quality paint, quality finish)

5) Depending on the expression the classifying is:

a). quantifiable characteristics: dimension, weight, durability,

b). characteristics tasks: defining the quality of the ratings (lack or presence of fungus in the wood texture).

A production of laminated wood should focus on following quality parameters:

1) Wood texture quality (technical features, the base, measured by comparison with a standard);

2) Quality of the adhesive used (technical features, basic indirect measure attribute);

3) The shape and sizing (technical features, basic, quantified and measured directly);

I mentioned the qualities that a wood product has to have for being a sustainable product, but I didn’t mention how hard it is to obtain these attributes. Wood has a lot of natural “enemies” that damage it and create a lot of problems for builders also. Darrel D. Nicholas says that the main factors that damage wood are termites, fire and fungi.

2.3.1 Termites

Termites represent a great danger for wood. Even Kristin Petrie starts his book with the question “Did you know that there are insects out there that can eat your house? These teeny, tiny bugs can turn wooden houses into dust. To make matters worse, these hungry troublemakers are sneaky about their work”( Petrie 2009).

Darrel D. Nicholas found a solution for those wood damagers. ”It is recommended for prevention and control of termite damage methods of construction and the use of chemically treated and unpalatable wood. It is recommendations stimulated both the revision of building regulations to reduce the damage created by termites and, in some states, the licensing of persons engaged in the practice of repairing structures damaged by termites”.(Nicholas 1973).

2.3.2 Fire

Human being is using fire since thousands of years and it can be a helpful tool but also an dangerous one. Sean Connolly says that “we all depend of fire in many ways. It can produce heat to cook our meals and warm our homes but it also has its dangers. Fire can injure and kill people and it can destroy the very homes that it heats. If it is not put out in time, a fire can quickly spread and destroy a much larger area. Knowing how to control fire is as important as knowing how to harness its heat. (Connolly 2003).

Fire is a real danger for wood because once started it’s very hard to be stopped. Like Darrel D. Nicholas says “fire has always been the nemesis of wood construction, but fire retardants that protect wood from fire or prevent wood from supporting its own combustion have contributed greatly to the fire safety of wood.” (Nicholas 1973).

2.3.3 Fungi

Fungi are different from other living things in many ways. ”Plants make their own food, but fungi cannot. Animals move around to find food, but fungi do not. Fungi also cannot digest food inside their bodies as animals do. Fungi feed by taking in nutrients from the material on which they grow.” (Pascoe 2003). Except the fact that that fungi are destroying wood it also affects its color. Like Darrel D. Nicholas says “fungi caused by far the greatest economic loss by discoloring and destroying wood.” (Nicholas 1973).

2.4.The process of making sustainable wooden components

Success or failure in making sustainable wooden components depends on the following conditions:

Perfect knowledge of customer needs. This includes not only the type and standard of the wood product, for example, equally important are delivery times.

Keeping the same or higher level of quality than the possibilities offered by manufacturers of prefabricated wooden components

This conditions are accomplished if the producer of wood components respects the three next steps:

Orientation to consumer needs;

Quality Assurance;

Diversification.

2.4.1. Orientation to consumer needs

Many times the process of determining consumer needs is reduced to a simple brainstroming session in the marketing department (sales) of the company. Lack of thorough research that includes surveys conducted among consumers is justified by the fact that such research requires time, effort and are very expensive.

The problem of classical surveys is that, often, the potential buyer is not fully honest or not fully aware of all his needs. In general all the requirements of the product offered to consumers can be divided into two categories:

a) basic requirements (critical) which are those without fulfilling consumer demands will not take into account purchasing the product offered.

b) ancillary requirements are requirements that are not strictly necessary after the point of view of the consumer, but which gives the product added value. Given a tough competitive environment, it happens quite often that some seemingly insignificant features of the product offered to make the difference between a successful sale and a failure. Any detail that provides value to the product or any service related product sales can create a high degree of comfort for the consumer to be analyzed and exploited at maximum capacity

2.4.2.Quality Assurance;

Quality control is an important aspect. Given that any deviation from quality standards will be punished hard by its customers it is important that the entire production process to be organized so that the product quality to be monitored continuously.

Elements of quality assurance:

1) Careful selection of raw material

2) securing the perfect raw material processing equipment

3) Quality control after each stage of production profiles

4) Ensure professionalism

      Execution profiles of wood is an activity that requires strict adherence to manufacturing. Since the first phase of the process flow, cutting blades that are required for professional using. Each dimension of the profile involves a certain size of timber and the use of specific methods of cutting in order to achieve a high degree of efficiency. Defects (knots, table resin, etc.) are removed from the timber using specialized automated equipment and parts are merged results "jointed" (coupling "finger join").

      The studies conducted by various laboratories and institutions have resulted identify solutions to minimize the number and intensity of defects, to improve quality. Thus, preventive treatments have been developed to prevent the degradation over time (in particular after water absorption). There is also a wide range of antifungal substances, both of which cause coloration and fungi causing material damage, decreased its specific weight. To increase the effectiveness of treatment, wood blanks major defects must not be dried and processed into final form. The safest method of protection is made by impregnating shallow depth or antiseptic substances (fungicides), which exerts a toxic action on fungi. To reduce the risk of fire, the wood can be processed by means constructive or chemical.

2.4.3.Diversification

Marketing policy objectives are to increase customer base and maintaining a high level of quality through continuous specialization and professionalization of staff. However, business strategy requires the beneficiary's orientation by creating performance systems that will be integrated in the tender.

A company that has diversification in his products is Palsgaard Group. Palsgaard Group is a group of specialists in prefabricated wood components for construction – trusses, dormers, roof, facade and floor slabs.

Some have called Palsgaard Group the Ministry of Wood. That is a good thing for this company because a ministry is in fact a place that brings together the best minds and the deepest knowledge of an area. And that is exactly what they have done. Over the years Palsgaard Group have become one of the largest suppliers of prefabricated wood components for the Danish construction industry and they have remembered to get smarter and better every year. The Palsgaard Group’s slogan is: Think natural, think possibilities, think tree!

III.Raw materials used in construction. Comparation with wood as raw material.

Building materials are natural or artificial materials used in construction. As raw material for manufacture of building materials are serving mineral origin (limestone, gravel, sand, gypsum, granite, marble, etc.), made ​​from plant material (wood, agricultural waste, etc..), Some products of metallurgy, industry chemical and petroleum processing industry (bitumen, polymers, tars etc.).

3.1.The Bricks

Brick is one of the oldest and most common construction materials, its existence is attested since 7000 BC, in the south of Turkey today, but in the Jerusalem area. At that time, the bricks were made of earth mixed with water, it was dried in the sun, then burned to become more enduring. The material was effective (preserving cool off in the summer, and heat in cold weather), to which we added other qualities, valid today – the natural regulation of humidity in rooms, absence of harmful compounds that could free inside etc.

Vestiges of the first brick houses have been discovered in today's Iraq, in the area between the Tigris and Euphrates, where he developed thousands of years ago, flourishing Mesopotamian civilization. Egyptians used dry ground and burned as construction material proofs exists in areas such as Harappa and Mohenjo-daro. Later, the Romans were the ones who made the difference between sun-dried bricks and burned in the ovens specially designed to increase their endurance. For the preferred material manufacturing during the spring, the Romans did not sell the finished product and not used for longer than two years. The use of mobile ovens allowed to introduce throughout the Roman Empire, these construction materials, each one is stamped with the insignia of the Legion who oversaw production. Their bricks were different from those in other areas, such as shape and in size – were round or elongated, sometimes rectangular, the raw material is clay with whitish and the reddish tint. In turn, the Greeks believed that most buildings that were, in their composition, walls with pieces of clay, placed perpendicular, were the most resistant, so they were used extensively in the construction of various public buildings. Bricks are used for exterior decorations, masters, in this respect, the Italian masons masters of the fifteenth century.

Early industrialization era brick production is the 1830 when Auguste Virebent, an architect from Toulouse (France), filed a patent for brick press, which might as well cut out the raw material in various forms.

Currently, the bricks are after wood most used construction material. Based architecture of terracotta and bricks inspired a huge industry that can annually produce hundreds of millions of pieces of various shapes, colors and textures. With the development of modern technologies, particularly robust engines and furnaces as tunnels giant brick making has become a much more productive and efficient. The basic raw material is represented by clay (most used compound), and calcium silicate and cement. Clay bricks, because they are the most popular currently have three different types of construction – by using very soft clays, the cold pressed and those with special designs. Starting with 2007, are made of building materials including ash from the power plants that burn coal.

High quality bricks have a huge advantage over other construction materials, by being the most resistant (can tolerate various weather conditions, acids, pollution and even fire). Can be manufactured according to the specifications, in any color, pattern, shape and dimes, much easier to build with them, than with cement and concrete, and having the advantage of a much lower price. However, it is good to know that there are some very porous bricks, which rapidly degrade if exposed for a long period of time to water. For best results, in any construction, correct materials should be chosen according to the specifications of the architect and engineer, to take into account, location, weather conditions, etc. local architecture.

At the first sight, we can say that brick is a better material than wood. But we have to analyse the environmental factor. Making prefabricated components from brick is harder, so bricks can be used only for industrial buildings. Also, the bricks don’t have any advantage for the climate.

As a conclusion, the brick is a good material for construction and the reasons are said in previous lines, but according to wood are more advantages using wood as a building material.

3.2.Cement

Concrete is a construction material that has the form of a fine powder obtained by processing raw material, which in contact with water, a plug and set. After hardening, retains its strength and stability even under water. Cement is mainly used for the production of mortar and concrete

The first form of cement was discovered by the Romans. Thereby replacing limestone with marl and marl lime kilns obtaining and increasing combustion temperature, obtained a material, finely ground and mixed with volcanic ash, cement is considered the first in history ("caementum").

Usually, cement isn’t it used alone in construction. The main reason is that concrete can affect health. The main risks to health are

skin irritation caused by fresh cement, which can result in burns to skin dryness and cracking of the skin;

Contact eczema, due to the presence of hexavalent chromium (chromium VI) and cobalt in the cement;

Eye irritation from splashing water with cement in the eye;

Rhinitis caused by inhalation of dry cement.

The cement is used for making concrete which is the most used construction material in the world.

Cement bonded composites are made of hydrated cement paste that binds wood, particles, or fibers to make pre-cast building components. Before using a wood in making cement bonded composites, its compatibility with cement is assessed.

Wood-cement compatibility is the ratio of a parameter related to the property of a wood-cement composite to that of a neat cement paste. The compatibility is often expressed as a percentage value. To determine wood-cement compatibility, methods based on different properties are used, such as, hydration characteristics, strength, interfacial bond and morphology. Various methods are used by researchers such as the measurement of hydration characteristics of a cement-aggregate mix; the comparison of the mechanical properties of cement-aggregate mixes and the visual assessment of microstructural properties of the wood-cement mixes. It has been found that the hydration test by measuring the change in hydration temperature with time is the most convenient method. Recently, Karade has reviewed these methods of compatibility assessment and suggested a method based on the ‘maturity concept’ i.e. taking in consideration both time and temperature of cement hydration reaction. (Karade SR, Irle M, Maher K , 2003)

3.3.Concrete

Concrete is a composite building material made from the combination of aggregate and a binder such as cement. The most common form of concrete is Portland cement concrete, which consists of mineral aggregate (generally gravel and sand), portland cement and water.

After mixing, the cement hydrates and eventually hardens into a stone-like material. When used in the generic sense, this is the material referred to by the term "concrete".

For a concrete construction of any size, as concrete has a rather low tensile strength, it is generally strengthened using steel rods or bars (known asrebars). This strengthened concrete is then referred to as reinforced concrete. In order to minimise any air bubbles, that would weaken the structure, a vibrator is used to eliminate any air that has been entrained when the liquid concrete mix is poured around the ironwork. Concrete has been the predominant building material in the modern age due to its longevity, formability, and ease of transport. Recent advancements, such as insulating concrete forms, combine the concrete forming and other construction steps (installation of insulation). All materials must be taken in required proportions as described in standards.

3.4.Metals

Metals in nature are presented as homogeneous materials with polycrystalline structure – grain conductive of heat and electricity. By melting together of several metals or elements after solidification, after some physical and chemical processes, alloys arise – who have different behavior compared to the main alloying element.

Like wood, metals have some technical characteristics that are very important in the building process. Those are:

Density metals – materials are free of pores and are characterized by absolute density, which varies from one metal to another.

Hardness – is a characteristic of metals that is appreciated by the size of footprint you leave a ball, a top a mandrel etc. on the surface of metal samples in certain test conditions.  This feature is important because it considers local compressive strength of the metal in various working conditions of construction elements.

Mechanical strength – is estimated by the values ​​obtained in the tensile or compressive. From the point of view of the mechanical, must be specified as the most important characteristic of metals and steels, in particular, is the tensile ( Hosford, Caddell, 2011).

From those characteristics we can say that metals are the perfect material that can be use in buildings. But before saying that, I have to analyze the disadvantages of using metals in constructions.

So, metals due to chemical and physical structure (crystalline – grains) are very susceptible to destructive chemicals.

Corrosion of metals can occur in two ways: chemical corrosion and electrochemical corrosion – facilitated by the formation of primary cells in a moist environment.

After the way they produce, corrosion of metals can be:

General (superficial) – occurs on the whole surface of the metal;

Local (punctate) – includes some areas forming dots, spots or hollows;

Intergranular – which occurs at the contact surfaces of the crystal grains;(Kesche, 2003).

But, like wood, are some methods of protections against corrosion:

Increases corrosion resistance by alloying with certain elements, in this way we obtain stainless steels and corrosion, effective but expensive.

A metal coating, which consists of covering the metal with low resistance to corrosion by a layer of a corrosion resistant metal (zinc, lead, copper, aluminum, etc..), Coating can be achieved by immersion in a bath of molten metal, by electrolytic deposition, by spraying molten metal (metallization) and the hot rolling of thin sheets of protection.

Chemical – which is achieved by coating metal parts with a layer of salt or corrosion resistant oxides (oxidation, anodising).

At the first sight we can say that metals are like wood. Are some riscs in using those materials in buidings, but every risc has its sollution.

For making a better comparation between metal and wood, I’ll describe the main metals that are used in constructions.

3.4.1.Aluminium

Aluminum is a white metal, light, flexible, resistant to atmospheric agents (by covering with aluminum oxide adhesive); is achieved through a complex process bauxite – alumina – aluminum in electric furnaces with high energy (25000 kwh / 1 ton aluminum).

It is used as an alloy because pure aluminum has low mechanical strength and can not be used in the technique. The most commonly used alloying elements are magnesium, silicon, zinc, and copper. The best known is though-aluminium alloy (alloy with magnesium) from which the profiles, plates, wires.

Aluminum products are used to achieve lightweight construction, in carpentry, metal work, as protective materials and finishes, electrical conductors, etc..

3.4.2. Steel

Steel is an alloy of iron with carbon (usually up to 1.7%), and other alloying elements. So the steels are obtained through cast (by reducing alloying elements) and by recycling old steels.

From the fabrication process, for steel, can guarantee a number of features, depending on which exists four quality classes, symbolized by the numbers:

1, when are guaranteed mechanical characteristics;

2, when are guaranteed chemical composition;

3, when are guaranteed mechanical characteristics and chemical composition;

4, when a character guaranteed the characteristics of class 3 and impurity content.( Bugayev,

Konovalov, et all, 2001).

Depending on composition they are divided into three classes:

Carbon steel, except if it contains carbon and other alloying elements in significant quantities, symbols of this type of steel is literary (OT or OL), followed by resistance to stretching.

Mild steel -they contain other alloying elements in small symbolization is similar to carbon steel;

Alloy steel when alloying elements are in quantities large enough to be able to mark on the characteristics of the steel; the steel such symbols start with a number that represents the carbon content in hundredths of a percent, following a group of letters indicating the alloying elements present in technical notation, a second number expresses the content in tenths of a percent of the principal alloying element (eg 23SM15 – indicates an alloy steel with 0.23% carbon, 1.5% manganese alloy but also with silicon composition).(  Boljanovic, 2004).

3.4.3.Copper

Copper is a reddish metal, ductile and malleable (can turn into sheets of thickness 2.6 mm), fusible (melting point 1083OC) good conductor of heat and electricity, corrosion-resistant.

Copper comes in a wide assortment of bars with different sections, strips, pipes, wires, etc.

3.4.4.Lead

Lead is a very malleable metal with low hardness, easily fusible (it melts at 3270C). Like aluminum, copper and zinc, lead is covered with a film of lead oxide, black, compact and adherent, forming a protective layer, but solvency is slightly warm water.

Lead has, in constructions, these uses: in the form of thick plates or insulation pieces are made from gamma rays and X, in the form of tablets come in waterproof insulation structure, lead pipes, obtained by extrusion, are used as a link to works plants (for water) lead oxide (Pb3O4), also known as red lead is used as a pigment (red) and anti-corrosion protection material.

3.4.5.Zinc

Zinc is a easily fusible metal (it melts at 4190C), brittle at normal temperature, it becomes malleable at temperatures above 1000C.

The main uses of zinc are anticorrosive protection of steel products (plates, pipes, etc..) , brass alloying element in solders, pigments for paints (zinc oxide and zinc sulfide white color), fungicide (for protection wood) in the form of zinc chloride.

After I presented some of the raw materials the next question is why should a consumer use a wood material and not another? I’ll present few reasons that can be considered a summary at my work:

Execution time required for a wood construction is very low, about 60 days after the order is placed, depending on the size and complexity of construction. This is because most companies that deal with such construction work with prefabricated modules that require only installation.

Cost of building a wooden building is up to 40% less than for a brick house.

Wood is easy to machine so you can opt for an extremely wide range of interior and exterior finishes. Moreover, wooden constructions can be covered with prefabricated materials to give them a modern design and beams can be covered with plaster – cardboard if you want your home to have a rustic look.

Wood is a good insulator so it will save money for heating in winter.

Buildings are very resistant in time, wood is renewable. In addition, wooden constructions have a better resistance to high intensity earthquakes, over 8o Richter since this material is more elastic.

The air inside a wooden build is never too dry or too wet for the wood helps maintain the optimum moisture in the atmosphere. A build that does not have problems with moisture will have a constant temperature.

IV. Analysis of the connection between theory and practice

We can say from the start that exist a connection between theory and practice. The idea with I started my work is that the world’s surface suffer a major lost of forests. To demonstrate that this idea is true we can notice the statistics from tropical countries. In south America the largest lost of forests was from 2000 to 2005 about 4.3 milions hectars, in Africa it was a lost of 4 milions hectars every year.

I also in my work, I sustain the idea that wood is an sustainable product. We can see the consumer’s opinions in forums, company sites.

Human economic activity is directed, as we know, to satisfy its various needs. The nature and intensity of these needs are in the stage of economic, social and cultural life of a company or a person (natural or legal), as well as customs and traditions existing in a country or territory. Basic human needs (food, clothing, heating, etc.) are essentiale as long as its standard of living did not exceed a certain limit.

Throughout its existence, a major concern for humanity was the provision of material and financial resources. More than that, the man led a struggle with certain forces of nature and society, which by their action necessary goods threatening its existence, life and affect bodily integrity.

So, using wood as an industrial material is a result at the human necessities.

V.Disscusions

The general construction of buildings and constructions of wood in particular there are plenty of factors that make the design work of which we can mention: the configuration of the structure, the choice resistance system, the dimensions of components and ease of laying. In the case of structures, wood joints design and implementation of elements is a behavior of particular importance for the operation and sustainability of construction.

Joints wooden elements appear necessary, first, because the forms and size that is normally supplied by means of which the timber can not be achieved always necessary openings or sections of the elements required by applications. On the other hand, the implementation of timber construction arises routinely need to merge together two or more care that converge at the same point forming knots.

There are currently multiple joint systems adopted on wood features made by builders and designers over time having the following roles:

– Development of composite sections, the assortment of wood is insufficient for the simple section to take requests (connections of solidarity);

– Extension wood elements to achieve the required length (joints extension);

– Achieving transmission effort between wooden elements when they make an angle between them (joints in knots or intersections).

Joints are mainly made to ensure the transfer requests products external actions between elements.

For a given structure, selecting a certain type of connection does not result only in terms of application and strength but also other conditions such as the architectural aspects, manufacturing processes and preferred execution, cost structure, etc..

It is thus impossible to specify a set of rules that allow the establishment the best system for a particular type of joint.

 However the choice of joining must be taken into account several conditions of which the most important are:

-Minimum possible loosening of parts joined together and therefore keeping the bearing capacity of thereof;

– Maintaining axialității efforts bars and avoid eccentricities that lead to change state of applications and the need to increase glued beam section;

-Ensure uniform distribution efforts bars components of composite elements and avoid overloading some elements;

-Harmonization efforts between successive connections and avoiding their destruction by using the combination of a single type of link and having the same characteristics;

-Split transmission elements efforts, while ensuring a higher number of working section and therefore avoid the negative effects of possible defects in the wood;

-Avoid the adverse effects of shrinkage and swelling as well as phenomena biodegradation (through stagnation, insufficient ventilation, etc.).

-Correlation type of joint used the product and the timber (roundwood, wood squared form of beams, planks or boards, etc..) and the environment of use (indoor, outdoor, and so on);

Joint-choice types that are susceptible to mechanical performance, easy to install and maintained, allowing control over technical and operational execution.

VI.CONCLUSIONS

  Protecting the environment is essential nowadays. We must think both us and the needs of future generations. In the last 20 years, Europe has realized that real lives over its possibilities and our way of life put to the test planet. Consume more and more natural resources and endanger environmental systems (water, soil and air). This can not continue indefinitely, especially as the world population continues to grow. It is important that forests can provide renewable materials and energy that can be used as a substitute for products and energy sources with high carbon consumption. More carbon in standing timber and wood products, and reducing the use of fossil fuels means less GHG in the atmosphere.

We must understand that human activities that lead to alteration or change component circuitry biogeochemical communities can hijack the meaning of ecological effects for the following decades or even centuries.

Natural resources are the engine of sustainable development. Environmentally sustainable development intertwined with the development of humanity, considering all aspects of human life in the context of major environmental issues of humanity. Current population needs should not compromise opportunities to meet previous life for future generations, the economic growth is conceived in harmony with the surrounding nature.

In the chapters presented I mentioned that using wood as industrial material is benefic for the environment. Also, using wood as a industrial material is benefic for the economic growth. From wood a manufacturer can produce a sustainable product if are accomplished the conditions I mentioned in my work.

So now I can respond at the questions:

Why are steel and mineral based building components still the predominant base for construction industry when wood is a more sustainable building material?

Is it more sustainable than steel construction or mineral based building component?

How about the energy that you invest for using the prefabricated wooden components?

=== bibl ===

Bibliografie

Harvey Green, Wood: Craft, Culture, History, Published by Penguin Group (USA), 2007

Dietrich Fengel, Gerd Weger, Wood: Chemistry, ultrastructure, reactions

Darrel D.Nicholas , Degradation and protection of wood, Syracuse University Press, New York, 1973

Richard Lewis Rees, Wood Houses, Published by teNeues Publishing Group, 2005

Kristin Petrie, Bugs Termites, published by ABDO Publishing Company, Minnesota, 2009.

Sean Connolly, Fire, published by Smart Apple Media, Minnesota, 2003

Elaine Pascoe, Fungi, Published by The Rosen Publishing Group, 2003

William F. Hosford, Robert M. Caddell, Metal Forming: Mechanics and Metallurgy, Cambridge University Press, 2011.

Vukota Boljanovic, Sheet metal forming processes and die design, Industrial Press Inc, 2004.

K.Bucayev, Y.Konolov, Iron and Steel Production, 2001.

Helmut Kaesche, Corrosion of Metals: Physicochemical Principles and Current Problems, 2003.

Site

http://cn.europeanwood.org/fileadmin/ewi/media/building-with-wood-c1.pdf

http://www.aboutcivil.org/Wood%20as%20construction%20material.html

www.palsgaardgruppen.dk/elementer/

www.taasinge.dk