**3. Timber buildings and sustainability**

*Timber Buildings and Sustainability*

**2. Wood in construction**

resulting in a setback in its use and its downgrading.

The advantages of wood in construction are various [2, 3].

perceived as comfortable only at higher surface temperatures.

control and standardization.

masonry.

Wood is one of the oldest building materials. In the past the great availability of material, the ease of processing and handling, and renewability, combined with specific qualities, have made wood the building material par excellence, for furniture, structural use, provisional, etc. Over time, wood technology and engineering have undergone an extraordinary evolution, but this domination has come to a halt since the nineteenth century, especially in countries where reinforced concrete and steel have monopolized the market. The reasons for this downgrading of wood are due to various cultural, economic, and environmental factors. These include natural degradability, combustibility, shape and size restrictions, and general distrust of a natural material that has inherent defects that affect its mechanical performance. Wood compared to other construction materials is characterized by the fact that the environmental conditions of installation can favor degradative or destructive alterations of biological origin to which the other materials are not prone, since they can instead be deteriorated by strong changes in temperature or by the action of gases and different chemical products that, on the contrary, leave the wood almost unaltered. The environmental hygrometric conditions do not have a significant influence on metallic and stone materials, while for wood they interfere with the values of mechanical strength. Furthermore, wood is characterized by a high susceptibility to fungus and insect attacks. Added to this is its combustibility. All these features have led to a negative view of wood as a natural construction material

In recent decades, fortunately, there has been an extraordinary turnaround of this material in structural use even in countries where its use had been downgraded or abandoned. A great stimulus is derived from the production of laminated timber, an industrial product that incorporates the greatest advantages of wood as a natural material with the reliability, constancy of production, and high performance of an industrially produced material, and therefore subjected to quality and process

Wood is a material characterized by good mechanical strength both in tension and in compression, so it can be used for the manufacturing of elements prone to bending such as beams, compressed like the pillars, stretched like tie rods, without the need to combine it with other materials, unlike for example concrete and

Wood is a material with a high strength to weight ratio, of the same order as steel, and it offers a compressive strength of the same order as reinforced concrete. Lightness is an important feature from the point of view of both strength and cost-effectiveness. In terms of strength, the reduced mass put into play by timber structures, for example, with respect to masonry, makes them less affected by seismic actions. In terms of cost-effectiveness, the use of a light material guarantees ease of manufacturing and handling and transport and minimization of the cost of supporting or foundation structures. Furthermore, the possibility of dry construction process allows rapid execution, modularity, and high degree of prefabrication. Wood contributes to environmental comfort due to its low conductivity, high thermal inertia, and natural hygroscopicity. Natural materials such as wood or cork are already comfortable at room temperature, while those like stone or cement are

Last but not least, the use of wood matches well the current trends of eco-compatible and sustainable construction as it minimizes the environmental impact at all levels as it is recyclable, renewable, biodegradable, and free of toxic contents.

**2**

The climate changes observed in recent decades, the global warming, and the increasingly frequent natural catastrophes are under everyone's eyes. In this context, the concept of climate protection summarizes all the possibilities that allow combating global warming as well as all measures to mitigate its effects.

The carbon cycle is the biogeochemical cycle through which carbon is exchanged between the geosphere, the hydrosphere, the biosphere, and the Earth's atmosphere. The current balance of the carbon cycle shows that CO2 that enters the atmosphere is higher than the one that comes out. Much of the emissions due to human activities cannot be balanced by the natural absorption of the oceans and terrestrial ecosystems such as forests and soils, and the increase in CO2 and other greenhouse gases leads to consequences such as the increase in global average temperature. In this contest, regarding climate protection there are basically two possible approaches: the reduction of climate-changing emissions (CO2 and other greenhouse gases) and the expansion of carbon reservoirs, the term carbon reservoir meaning any stored form of CO2. Wood allows both roads to be traveled [4, 5]. Thanks to photosynthesis, a tree can store large quantities of CO2 in the wood. It is estimated that 1 m3 of wood stores approximately 1 ton of CO2, which remains stored in the material throughout its life, even when the wood undergoes the transformations that make it a semifinished product or a finished product, for example, for the building industry, starting from the raw material. Therefore, the use of wood in construction involves two fundamental advantages: on the one hand, the gradual replacement of the most energy-intensive and polluting building materials with timber reduces the climatechanging emissions associated with the production and management of these materials; on the other hand, the management of forests aimed at the use of wood in industrial sectors such as buildings involves the continuous renewal of the forest itself with an increase in the capacity to extract CO2 from the environment.

In addition to the strictly environmental sustainability aspects, the impulse to use wood in construction involves aspects of economic and social sustainability. The possibility of implementing short supply chains based on the use of local wood, for example, makes it possible to reduce the energy consumption linked to transport from distant areas of growth and at the same time allows to create employment in areas far from urban centers and therefore often economically depressed. The wood market is constantly expanding given the considerable possibilities of use, the high performance, and the technological progress of this material. The impulse to use timber in construction, especially if connected to short-term production chains, can allow:

