Introduction to Case Studies

Beside new design and materials the present architectural practice is focused on the energy performance of new buildings and the ones to be renovated as well. Most of the existing buildings are residential buildings, which usually need a kind of modernization and improvement of the energy efficiency. The main aspects of the improvement of energy performance of the buildings is minimizing their annual heat energy demand and optimizing their indoor comfort.

The first step of the energy rating is calculation of the annual heat energy demand of the building. This calculation is performed using the simplified calculation method described in EN ISO 13790 (replaces the EN 832, which was recently cancelled) or national standards respectively. The calculation is based on a steady state energy balance, but taking account of the internal and external temperature variations and, through an utilisation factor, of the dynamic effect of the internal and solar gains. Using this simplified method the calculation of the annual heat demand and check of the modernizations alternatives is fast and simple.

front view 1 In order to perform a more exact calculation of the energy performance of the buildings the computer simulation methods will be used. The computer simulation methods are based on the solution of the thermal building models in the short time steps (hourly frequency). The use of the computer simulations is contingent with the requirement on the exact determination of the annual heat energy demand of the building. It is made by the analysis of the complete building systems and application of the new buildings materials, construction and technical establishments. One of the most advantages of the computer simulations is the possibility of detailed analysis of the influence of every building part to the overall behaviour of the building. It is possible to follow the state of the building and its rooms during the year in hourly time steps and, eventually, to correct the mistakes of the project (unproportional thermal insulation thickness, increase of the absorption surface).

front view 2 Not only a heat use and a mean heat transfer coefficient is reduced by the thermal insulation of the facade and the roof and through replacement of the windows, but also the indoor environment is altered. This happens with the unproportional thermal insulation thickness and leads in summer to overheating of the rooms, which lowers the indoor comfort of the living space. Under circumstances the summer overheating can be corrected using suitable sun shades or ventilation/cooling systems.

Within the presented examples the computer simulations of the following aspects were used: the annual heat demand for heating and cooling, regulation and optimization of the building technique, evaluation of the visual and thermal comfort of the living rooms (interiors), rational application of the new building materials, construction components and systems in real objects, with assessment of their influence upon the thermal behaviour of the building. The computer simulations were applied in terms of the project CAB to create simple modernization examples for architects and demonstrate the advantages of using simplified computer simulation methods in the practice of the small architectural offices.

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