The position of the sun has been simulated along the whole year in order to evaluate its influence and project actions to avoid heating during the summer and to favour solar exposure during the winter.

This will be of special interest for rooms of general used, which will thus be facing South. Figure 3 shows the trajectory of the sun for all months, referred to the concrete location of the building. The aim is to avoid shadowing by surrounding buildings.

2.1. Insulation

The process of thermal energy transmission in a building of these features takes place mainly by radiation process (75%), but also involves residual conduction and convection (25%). Therefore, any type of building insulation project should be designed mainly to impede the radiative thermal energy flux, but it should also account for residual conductive processes. This way, reflective insulation appears as the most adequate and efficient technique, provided very high output due to high reflective power and to the specific structure for the retention of air bubbles.

The results achieved by reflective insulation (versus traditional methods) are quite significant. Figure 4 shows the thermal resistance for several types of insulation (values of thickness between 1-10 cm, with 5 mm step interval).

Reflective insulation presents a flat curve from a concrete value of the air chamber thickness, and efficiency is not improved for higher values. However, thermal resistance is significantly higher than that of a conventional insulating material. In sum, this feature favours the optimisation of useful interior space.

Let us describe as an example the insulation pattern projected for both South and West facades of PETER building, following the actual order of the insulating coatings:

• Marble shield (model Frontek de Venatto), 2 cm thick.

• Low-emissive air chamber (4 cm).

• 4 mm Superpolynum reflective insulator, with intrinsic resistance 0.11 m2 K W"1.

• Structural panel (12 mm).

• Natural fibre insulator (25 mm).

• Low-emissive air chamber (2 cm).

• 4 mm Superpolynum reflective insulator, with intrinsic resistance 0.11 m2 K W"1.

• Low-emissive air chamber (4 cm).

• Laminated plaster sheet (15 mm).

The total transmission coefficient of this type of wall is U=0.31 W / m2 K.

The next step is the comparison of the thermal conductivity parameters with those of the TBC, DB — HE 1, which indicates the maximum limitation of the energy demand of a building, considering maximum required transmittance according to the type of walled enclosure and to the climatic zone of the location of the building. Taking this aspect into account, a detailed analysis of the energy demand shows energy savings over 69% in winter and over 86% in summer with respect to the values stated by the TBC (see Table 1).

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Such a reduction of the energy demand will lead to lower power in the heating and the acclimatisation systems. Besides, if renewable energy devices were installed, then fossil fuels or conventional energy sources would not be required. The use of those devices would not only result in environmental benefits, but also in notable economic savings.