PROVIDENCIA, VOLUNTAD, DESTINO

The thermal characterization of natural (1), chemical treated (2) and heat-treated (3) Radiata-pine is assessed. For that, the test box procedure previously described in Chapter 2 is followed. In this case, a correlation between their characterization results presented in Chapter 3, section 3.2.2.3, is realized.

The deteriorated samples were tested though test “a”, previously described in section 3.2.2.2, which corresponds to a gradient of temperature between 9 and 11 °C among sample faces, with 40°C temperature inside the test box and 21°C outside. In this case, both original and ageing samples were tested at the same time in order to compare them with similar boundary conditions, as both temperature and humidity influence the wood thermal behavior, as it was previously studied in section 4.2. In this case, the relative thermal conductivity is obtained.

In Table 5.19, there are shown the results obtained by the three samples. A difference between the original samples conductivity (λ) and those after deterioration (λ´) is realized.

λ λ´ Δλ

[W/(m∙K)] [%]

1 0.1202 0.0821 -31.65

2 0.1205 0.0898 -25.44

Table 5.19. Thermal conductivity variation between original (λ) and elder samples (λ´)

If the results presented in Table 5.19 are analysed, a decrement of the thermal conductivity after the deterioration is obtained. This fact makes the material more insulated than previously. That is, it is demonstrated that deteriorated Radiata-pine has lower thermal conductivity than original one.

5.5 Conclusions

As it was previously mention, during the first period of time, from January to March 2015, there were sunny cloudless days, rain and even snow during some days. The sharp and fast variation of those elements makes deterioration of the samples growing up faster. The most remarkable appearance changes take place from March to April, when the material is not adaptable to environment yet. In fact, there is a huge difference in colour between these months. While during March the colour is similar to original one, in April both natural (1) and heat-treated (3) sample become grey. However, chemical-treated one (2) changes from green to pale brown colour, turning its appearance to more natural colour.

After April, both natural (1) and heat-treated (3) Radiata-pine samples appear to be the same, which makes difficult to distinguish them. In terms of cracks they are also similar, which are wider than the fissures of the chemical treated sample. If rugosity is analysed, natural and heat-treated Radiata-pine also presents the most variation, while chemical treated Radiata-pine keeps less deteriorated after two year.

However, in terms of thermal behaviour, the least variation of thermal conductivity after a year weathering is presented by the heat-treated wood (3), while the natural wood (1) presents a variation more than two times higher. In case of chemical treated wood (2), its difference respect to Sample 3 is lower than Sample 1.

Although the third sample (3) is the most stable material, in terms of thermal conductivity, the conductivity variation of the first sample (1) is the most beneficial in terms of energy efficiency.

“Education is the powerful weapon which you can use to change the world”

Nelson mandela 1918-2013

6 Sustainability

The environmental factor is of key importance in terms of the outlook for global sustainability. The actual environmental crisis on the planet, where resources are becoming scarcer every day [101], implies environmental degradation due to problems linked to global warming, acid rain, and ozone depletion of the stratosphere, among others. Many of these effects are attributed to continuous industrial development on our planet. Thanks to sustainable development, there is today a greater awareness in society across all sectors and many actions are underway to reduce the impacts generated in the environment. As Jain and Jain noted [102], in the final analysis, development and the environment are in all probability not independent dimensions.

In this sense, the construction sector has a lot to answer for, as it is one of the principal drains on natural resources and energy. As an example, during their ‘lifecycle’ (including building, maintenance and demolition), buildings are ‘responsible’ for 50% of total energy consumption and for 50% of total CO2 atmospheric emissions [103].

Many of the actions in this sector concentrate on the use of materials with higher sustainable rates, in the widest sense; in other words, materials that are recyclable, reusable or naturally renewable, as in the case of timber [104-108], As switching over to certain materials may not be globally achieved immediately, because of the disruption to present-day industry that such changes would cause, this process should be gradually developed. So, firms should continue to adapt to demand in society through product

development, while striving to incorporate these new environmental requirements in their products [109].

Over recent decades, different procedures and methodologies to analyse the sustainability of buildings have been developed [110-114]. Some of these tools assess economic and social components, as well as their environmental impact, which are the 3 basic pillars of sustainability [115, 116]. Moreover, the governments of various countries have participated in this process and have been introducing directives and standards that generalize this process of improvement. In the case of Spain, the regulations currently in force - the Technical Building Code [6] has introduced measures related to the minimization of water and energy consumption as well as other materials in the building process [117].

Moreover, the characteristics of wood as a building material, in terms of both strength and the environment, make it an ideal material for the construction of buildings. Even so, it is important to take into account that, as with all materials, wood has to comply with a series of standards, so that it is used as efficiently as possible from an environmental standpoint.

Hence, the main purpose of the present chapter is to develop a methodology to address the degree of “environmental sustainability of wood cladding”, by assigning a numeric value, on a scale between 0 (minimum) and 1 (maximum), to different enclosure solutions (scenarios) [118]. Those scenarios will be proposed at a project design stage for a particular wooden enclosure, making it possible to select the most environmentally sustainable option to execute the project.

6.1 Assessment model for environmentally friendly cladding