Financial viability of energy-efficiency measures in a new detached house design in Finland

This study analyses alternative energy-saving design concepts for a typical new detached house design in Finland. The impact of these design concepts on the construction costs and on the total delivered energy needs of the building were calculated, and the financial viability of the different concepts analysed. Different thermal insulation and airtightness properties of the building envelope and different ventilation's heat recovery efficiency assumptions were tested in the analysis work. Other variations modelled included the heating mode: direct electrical floor heating, or floor heating via an air or ground source heat pump. Among these alternatives, the estimated annual consumption of purchased energy for running the household varied extensively, in the range 57-182kWh/net floor m². With the real interest rate set at 3%, the payback period was shortest for the air source heat pumps (9years). When a heat pump was installed in a house with higher energy consumption, the payback period was 7years, and if it was installed in the 'ultra low-energy' house designs, the payback period was over 13years. Investment to thick thermal insulation of envelope was unattractive in Finland. The results of this study can be generalized to similar climates and techno-economic environments.