Energiansäästömahdollisuudet rakennuskannan korjaustoiminnassa

The study estimates the feasible energy savings potential in the 2010 building stock by 2050. The focus is on energy-saving measures related to renovation of residential and service buildings. The calculations were done by building types and age groups using the EKOREM calculation model. The calculations indicate the building types and structural elements where potential for savings exists. The study did not consider energy-saving measures related to changes in heating systems, electrical equipment, property maintenance or use habits. The study disproved the common belief that considerably more energy savings could be achieved faster by focussing on the existing building stock instead of new construction. That is mainly due the fact that it generally pays to implement structural energy-saving measures only when the targeted elements also require other significant repairs besides energy-efficiency improvements. Thus, energy renovations cannot be speeded up very much. The clearest exception are the extra insulations added to roof assemblies that are easy to implement. Attempts to save more energy in the building stock than can be achieved at a small additional cost in connection with needed renovations may multiply costs, and the saving in energy costs will not necessarily cover the additional investments. The efficiency of energy-saving measures can be affected by recommending or ordering use of more energy efficient windows, thicker extra insulations or more efficient ventilation heat recovery systems than the standard solution selected in connection with renovations. The goal of preserving the characteristics of buildings of cultural-historical or architectural value and the typical solutions and materials used in all buildings of a certain period limit the repair and renovation of structural elements. In the case of these buildings, improvement of energy efficiency can be considered in connection with the planning of renovations and the buildings’ use and maintenance. Residential buildings, about 70 % of which are owned by private individuals, play a major role in renovation. The owners cannot be enticed or ordered to implement renovations that they do not find sensible or cannot afford. Especially in areas facing an uncertain future, the financial capacity for expensive renovation measures is low. In theory, it is possible to save considerably more energy than is considered feasible. The theoretical savings potential was estimated by making the entire residential and service building stock correspond to 2010 energy regulations for new construction in the calculation model. That resulted in about 40 % savings in the existing stock. That level is, however, realisable only in the case of individual buildings. Since some buildings and structural elements have already been renovated, and some will not be renovated for various reasons, a maximum of half of this theoretical savings potential in the entire building stock (about 20 %) will be realised by 2050. The limiting factors are technical, economical, functional and decision-making related. The key piece of input data for calculations was the number of renovation operations in connection with which energy-saving measures can be carried out. An average of about 2 % of structural elements are repaired annually. More windows are replaced than other elements. Annual energy savings depend on the rate of renovations and the energy efficiency of selected solutions. The feasible annual extra savings in heating energy from renovations varies from 0,2–0,7 % in the case of the existing residential and service building stock. In 2020 the cumulative annual savings would thus be 2–7 % and in 2050 8–28 % compared to 2010. The in-between values can be interpolated linearly. Based on the calculations of this study, the realisable savings potential in the current building stock would be about 20 % in 2050. That is assumed possible, but without intensified energy-saving measures, the savings could be only half of that. The biggest uncertainty in the estimation of savings potential is related to increased ventilation heat recovery especially in blocks of flats. Based on calculations, the energy consumption of the residential and service building stock in existence in 2010 will drop from 91 TWh/a to less than 50 TWh/a in 2050. Consumption will be reduced by structural energy-saving measures, changes is heating methods and loss of stock. It is possible to attain nearly 20% savings, about 10 TWh/a, in the 2010 building stock through renovation measures by 2050. The greenhouse gas emissions from the energy used in buildings will be cut by energy savings as well as an increase in nuclear power-generated electricity and wider use of renewable fuels in the generation of district heat and electricity. Moreover, emissions will be reduced, especially in detached houses, by switching to heating systems that produce fewer emissions. These changes in energy supply will probably cut the green-house emissions of the building stock more than energy-saving measures in buildings. Yet, both are necessary to attain the reduction goals.