3.1 Analysis of the base-case design

As stated in section 1, the first criterion to fulfil the regulation RCCTE is that the envelope obeys to certain minimum requirements. Table 4 shows the results of the evaluation of the base-case retrofit design against the requirements of RCCTE. The results show that several envelope elements do not fulfil the minimum requirements of the regulation.

Four out of the six analysed apartments do not comply the requirement for the U-value, because no insulation was foreseen in the design. Another four apartments do not comply with the requirement for the maximum solar factor of the windows. This is mostly because they foresee a thick layer of low-weight gypsum at the internal face of the walls and ceilings, which cuts the effects of the thermal inertia from the walls and slabs, resulting in low thermal inertia. The maximum solar factor allowed for buildings with low thermal inertia is only 0.15, so the windows with internal curtains do not fulfil the requirement. The solution may either be to increase the thermal inertia to medium, or to adopt external shading which leads to solar factors below 0.15 (the first solution seems more advisable here).

Planar thermal bridges are also subjected to quality requirements but none was identified in the apartments analysed, because the structure essentially relied upon the massive granite walls, so no concrete beams were identified.