2.1.2. Analyze the elements of the building envelope

2.1.2. Analyze the elements of the building envelope Building envelope has the function of enclosure in the building, considered as a shell. Such element functions as a threshold between the interior and outdoor environment, between private and public. The building envelope includes several spatial elements such as external walls, floors, roof, ceiling, windows and doors (figure 2-1). All of these components are indicators for the amount of energy required for the building for thermal comfort. However, the loss of energy is depended by several factors, which include climate of the context, construction technique, longevity of the building, building typology, users’ behavior and location of the building.

Figure 2-1 Building Envelope components (Source: IEA 2013) There has been a significant improvement in the code requirements of the building envelope, an improvement in performance which is still in progress throughout years. As a result, there is increasing request for developing new materials which provide thermal insulation and low transmittance values, which is differently known as U-value (table 2-1). This value is the quantity of heat transmitted in a structure, whether it is made of a homogeneous substance or a composite, divided by the temperature differential across the structure. Watts per square meter per Kelvin (W/m2K) is the unit of measurement. Such U-value must be as low as possible to have a good insulation of the structure and is defined also by the standards of the insulation and the method, which should be as fit as possible to avoid gaps and cold bridges, in order to avoid high levels of thermal transmittance (Sadineni, Madala, & Boehm, 2005). The term "thermal transmittance" refers to the heat loss caused by conductivity, diffusion, and radioactivity

Table 2-1 Standard U-values (in W/m2 K) (Source: John G, 2005)

 Walls The main element in the building envelope is the external wall, by which it is provided thermal and acoustic comfort in a building, but along with such performance it is necessary to have aesthetic consideration which may have its indication in the context where the building is positioned. The thermal resistance of the wall (R-value) indicates the level of energy consumption. The proportion of wall to total exterior sector is high in tall structures. The market-available center-of-cavity and transparent wall R-values take thermal comfort into account. High structures most of the time were constructed by providing energy conservation through thermal mass, without considering insulation, which is very important and is found in many technical solutions and variety of materials that can help the aesthetics of the building at the same time. 44