In Slovakia until year 2000 they have built 18,386 dwelling houses with total number of flats 747,000 which accommodates 45% of the Slovak population. Until 1950 the residential buildings were built from bricks with a square roof (mostly wooden construction) and in period 1951-1970 the apartment buildings were prefabricated made from light porous concrete. And in period of 1971-1983 they are beginning use of laminated lightweight construction with sandwich. In Slovakia, 90% of oil and gas are supplied from Russia. Therefore the Slovak government focuses on protecting the environment and reducing the energy consumption in buildings.
Dusan talked about a special renovation project where the focus was on improving efficiency of a building envelope, optimizing of heating system and hot water usage. In Dusan´s project they use special software for energy calculation which has a database of 42 apartment buildings and 8 typical single family houses and are countable in two climatic zones with design temperatures of -12°C and -18°C. The software structure contains photo documentation, drawing documentation, building description, energy & economy calculation and energy audit details. The energy & economy calculation include calculation of energy savings, investments and profitability. In this case the three basic domains of detailed energy measures are improvements and optimization of building envelope, heating system and hot water usage.
Energy savings measures in a building envelope include insulation of external walls, insulation of floor towards unheated basement, insulation of a roof and installation of new windows. Energy savings in heating system focus on automatic control system and temperature setback for heating system, insulation of pipes and valves, reconstruction of boiler room including new boiler and accessories, and balancing of the heating system and installation of thermostatic valves. Energy savings in hot water usage are based on installation of water saving shower heads, thermostatic mixers and showers, insulation of pipes and new valves including installation of new automatic control system on hot water system.
The investment costs for improvements of these three systems include costs of supplying, design work, installation, running and pressure tests, and tax. The energy potential in application of these measurements are approximately 20-30% in building envelope, 10-25% in heating system and 5-10% in hot water optimization.
The case study of renovation of concrete apartment building (i.e. panel building), one of the dominant types of buildings in Slovakia, has the following objectives: to clarify relationship between energy consumption, energy efficiency measures and the indoor environment, and to study occupant´s behaviour and habits. The results show the energy saving potential in three points: before renovation, after renovation with no-balanced heating system and after complex renovation.
Dusan´s case study is a prefabricated panel building built in 1987 with 9 storey and 32 apartments. The heat is delivered from heat exchange station supplying heating and domestic hot water. After application of above described measures the energy audit shows saving of 66%, i.e. the actual measured consumption decreased from 248,472 to 190,733 kWh/(m2.a) after insulation of façade & roof and replacing of windows, and further to 93,095 kWh/(m2.a) after hydraulic balance of the heating system. And the energy class was changed from class D to class B, i.e. from 106 to 35 kWh/(m2.a).
Also the subjective evaluation of indoor climate was performed using questionnaires where after renovation the level of thermal comfort was improved from just acceptable to clearly acceptable, i.e. the perception of temperature improved from 0.18 to 0.52 PMV. Also the situation with drafts, cool windows, cold floors towards basement and cold ceiling under roof were improved by almost 80%. After renovation, the people felt less need to adjust thermostatically the temperatures, i.e. the need decreased by 54%.
The conclusions of Dusan´s presentation were: convenient energy-efficient and economically feasible measures decrease energy consumption and improve indoor environment, behaviour has a significant impact on indoor environment and can affects high energy consumption. The suggestion are that to improve indoor environment one has to know how strong occupant impact to thermal comfort and to find all influencing aspects.