Doctoral Thesis in Civil Engineering
Sandra Cristina Alves Pereira da Silva Cunha
University of Trás-os-Montes e Alto Douro, Vila Real, Portugal
Anthropogenic effects on the natural environment called the attention of the research community, leading to intensive study of environmental issues, namely to those related to climate changes. One of the major milestones towards resolving these issues was the Kyoto Protocol, which aims to limit emissions of greenhouse gases.
The improvement of the thermal performance of buildings will contribute, in the medium and long-term, to the compliance with international environmental obligations. This is an effective way of reducing fuel consumption and consequently the level of emissions. In Portugal the energetic certification system, called SCE, and the Portuguese Regulation of Thermal Behaviour of Buildings, called RCCTE, require designers and constructors to meet higher levels of quality.
In this research project, a methodology to evaluate “in situ” the thermal behaviour of external walls of residential buildings, using a heat flux measurement system, is proposed.
It is believed that this non-destructive methodology can be more effective and reliable than existing methods and adequate to be used by the experts responsible for the enforcement of the energetic certification system. This work follows on from scientific studies aimed at better understanding heat transmission through the residential buildings external envelope.
In order to corroborate the proposed methodology, experimental work has been carried out. The tests consisted on “in situ” measurements to evaluate the thermal behaviour of external walls of residential buildings in the city of Vila Real. The final results show that the values of thermal transmittance coefficient (U) obtained in the measurements and the ones calculated in the design phase converge. Two important factors for the success of the measurements were identified: (i) the interior temperature must be stable; (ii) the temperature differential between the interior and the exterior of the building should be significant. The work shows that the proposed methodology can be used in evaluation and energy certification of buildings, since the results were reliable and duration of tests advocated may be lower than the 14 days mentioned in the bibliography, which enhances their practical applicability. However, in order to make the proposed methodology operational, it is still necessary to perform a wide range of systematic tests, namely to establish the boundary conditions of its use.