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The article applies the global costs calculation method to the energy assessment of selected solutions for the technical equipping of buildings, dependant on their purpose and function. Representative archetypes, the life span of which were assumed to be 30-years, were used to estimate the performance of the minimum requirements according to the building regulations valid in 2013, current general standards, as well as low energy building and passive house standards. The subjects of the analysis were three residential buildings, for which the variability of the cladding and ventilation needs was assumed. In all analysed cases the application of four systems of energy supply to the building was also assumed. The optimal level of primary energy index value, dependant on the source of heat, was established by means of the global cost method. This level was then compared with the requirements presently valid in Poland. The analysis also allowed for the determination of the growth in investment costs, that must be considered in order to achieve the energy needed for heating and ventilation at the level of 40 kWh/m2/a or 15 kWh/m2/a. The analysis presents a comparison of the subsidized loans for energy-efficient houses offered by the Polish Government.

The energy-saving requirements for most buildings focus on improving the insulation and airtightness of a building’s envelope. In this paper, the authors have investigated the effect of additional internal insulation on energy consumption for heating and cooling in a residential building. Energy performance analyses were conducted for buildings with four internal thermal insulation systems in three locations using the WUFI Plus software. The Global Cost Method and Simply Pay Back Time have been used to assess and compare the economic viability of the retrofit systems. The results show that, in relation to energy, retrofitting with internal wall insulation can be an alternative to traditional external insulation. The assessment of internal insulation for low-energy buildings, however, cannot be conducted based on economic criteria. The usual approach of Simply Pay Back Time has exceptionally long payback time, which is unacceptable. In turn, the Global Cost Method, can only be used to compare the applied materials. With high investment costs, thermo-modernization improvements do not contribute to significant savings. The conditions of thermal comfort and the analysis of temperature and steam pressure play a decisive role in assessing this type of solution.