Changes to achieve class A+
The results of table 9 show that, with a proper selection of energy supply equipments and vectors, it is possible to fulfil the regulation and to achieve class A in all locations and even class A+ in some locations. It is however important to clarify if class A+ can be achieved in all the studied locations. In order to assess this, a new round of improvements was implemented for the locations where class A+ had not yet been achieved. The improvements consisted on the adoption of a better solar collector and on several improvements to the building envelope. Table 10 shows a detailed list of the improvements made at each of the locations where the A+ had not yet been achieved.
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Table 10: Changes implemented to try to achieve class A+.
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Dwelling |
- Better solar collector (h0=76%, a1=2.8) + Wall insulation increased to 8 cm (U=0.32) + Insulation of interior envelope walls increased to 8 cm (U=0.32) + Windows with low-e glazing and plastic frame (U=2.0) + Floor slab insulation increased to 8 cm (U=0.32) + Mech. Vent. 0.6 ach-1 + heat recovery 70% |
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Viana do Castelo |
Apartment |
- |
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Dwelling |
- Better solar collector (h0=76%, aj=2.8) + Wall insulation increased to 6 cm (U=0.45) |
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Lisbon, Faro, Evora: No changes required |
Table 11 and Table 12 show the results after this new round of improvements. The results confirm that class A+ is reachable in all locations both for the apartment and for the dwelling. The level of constructive and technological sophistication differs according to the building and location. For the dwelling in Guarda and in Penhas Douradas, reaching class A+ implied adopting mechanical ventilation with heat recovery, a solution not common in Portugal so far.
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Table 11: Results for the apartment after the changes to try to achieve class A+
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Table 12: Results for the dwelling after the changes to try to achieve class A+
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1st International Congress on Heating, Cooling, and Buildings, 7th to 10th October, Lisbon - Portugal /
NC. = Not Compliant |
This study analysed the compliance of different sets of constructive and technological solutions of two residential buildings with the thermal regulations in different places in Portugal, as well as the corresponding energy class.
The first major conclusion form the results is that it is possible to comply with the regulation and to achieve the best energy classes (A and A+). Since the studied locations included extreme cold and extreme hot locations of Portugal, it is possible to infer that this holds true for the whole country.
The second major conclusion is that the requirements for the envelope are determined essentially by the need to comply with the heating requirements. It was found that the thermal quality level of the envelope needed to comply with the regulations is substantially different between the mildest and the coldest regions of the country. While 3 to 4 cm of insulation seem to be enough in the locations close to the coast, the interior mountains regions it may require about 6 to 8 cm. Nevertheless, compliance seems to be possible without interfering significantly the architectural appearance of the buildings (glazed area, solar orientation).
Regarding the energy class, it was found that is determined essentially by the equipment choices for heating, cooling and domestic hot water, with a decisive influence of this later one, due to the weighting factors 0.1 / 0.1 / 1.0 used in equation 1. In this aspect it was confirmed that a solution of domestic hot water heated exclusively with an electrical resistance seems to be incompatible with the regulation. Nevertheless, optimization of the envelope seems to be also needed to make difference for class A+ in the coldest regions, and in some cases even mechanical ventilation with heat recovery may be required to reach that energy class.
Regarding the importance of solar collectors, apart of the issues of its obligation and of the reasons that allow to drop that obligation, it is clearly demonstrated by the fact that they were part of all the sets of solutions that achieved class A+ and of most of those that achieved class A. Naturally, since Ntc is evaluated in primary energy, solutions of solar collectors complemented with gas boilers lead to better results than those complemented with electric resistances. In the coldest regions where class A+ is more difficult to achieve, a high quality solar collector (or a collector area higher that strictly required by the regulation) is one of the most effective elements in finding solutions towards class A+.
[1] Regulamento das Caracteristicas de Comportamento Termico dos Edificios - RCCTE, Decree-Law 80/2006 in Portuguese).
[2] Sistema Nacional de Certificagao Energetica e da Qualidade do Ar interior dos Edificios, Decree-law 78/2006,
[3] CAMELO, S. Camelo, P dos Santos et al.: Regulamento das Caracteristicas de Comportamento Termico dos Edificios (RCCTE). Manual de apoio a aplicagao do RCCTE (in Portuguese).
