In modern construction trends, the construction of lightweight prefabricated buildings is increasingly gaining ground. The public opinion mostly sees its main advantages as compared to traditional heavyweight brick construction in shorter construction times and energy efficiency in terms of very low heat transfer coefficients between individual construction assemblies. A fundamental shortcoming, often disregarded, is the lack of heat capacity of the building itself. The existing research indicates that, as a consequence, such buildings are experiencing overheating problems during the summer to an ever greater extent. This results in lower thermal comfort and greater energy wastage of the building in the event of active cooling.
The main purpose of this thesis is to compare heavyweight and lightweight construction in terms of the parameters of thermal comfort and energy efficiency in the summertime. The comparison also included lightweight construction with phase change materials (PCM) integrated with the aim of improving the thermal stability of the buildings. For the purposes of the thesis, we considered five different building envelope structures: heavyweight construction, lightweight load-bearing structure, lightweight frame structure, and two examples of lightweight frame structures with PCM. The structures were compared with each other both in terms of thermal comfort (internal air temperature and operative temperature) and energy efficiency of active cooling of the building in the summer period.
The selected thermal comfort parameters (internal air temperature and operative temperature) and the energy required for cooling were calculated using the DesignBuilder software tool. A characteristic week in August was selected, the parameters were monitored with a time step of one hour, on the hour. The evaluation of the results relied upon the legislation in force in the Republic of Slovenian for the fields considered.
The results showed that the highest internal air temperatures in the case of the heavyweight load bearing structure were on average 0.9 °C lower than in the case of the lightweight frame structure envelope. Internal air temperature in the case of the lightweight load-bearing structure envelope is comparable to that of lightweight frame structure envelope. The thermal response of the lightweight building envelope with a sufficient amount of PCM proved similar in terms of internal air temperatures to that of heavyweight construction. Similar findings were revealed by the results obtained for operative temperatures, with slightly greater discrepancies between the different building envelope structures (average 1,1°C). In accordance with the operative and internal air temperature results obtained, overheating of the structures studied and cooling demand for active air conditioning of the buildings was established. In the provision of adequate living conditions during high external air temperatures, the heat capacity of the building proves to be of great importance. The examples of PCM use show that the desired effect can only be achieved by selecting appropriate parameters, such as the amount and the melting point of the materials. The said effect is manifested by reduced operative and internal air temperatures as well as their daily fluctuations and, consequently, a lower cooling demand for cooling the buildings.
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