Energy renovation technologies and saving potentials of Finnish buildings

VTT's Energy renovation technologies-project studied the profitability of energy renovation measures for buildings. Different energy renovation technologies for structural improvements (retrofit insulation, air tightening), heat supply systems, ventilation systems, lighting, electrical appliances, solar shading and cooling, were evaluated. The effects of different energy renovation measures to reduce heating or cooling energy were simulated. The calculations were made for two single-family houses, three apartment houses and one office building. The energy consumption of the example buildings was simulated before and after the renovation. The heating systems of the two studied single-family houses were direct electrical heating and water central heating with an oil-fired boiler. Common energy renovation technologies for the houses were retrofit insulation to fulfil the present heat insulation regulations, air tightening, and changing the mechanical exhaust ventilation system to a mechanical supply and exhaust ventilation system with heat recovery. The effect of an outdoor air heat pump, a ground heat pump and solar heating system were evaluated, too. The combined renovation steps reduced the annual electricity consumption of the electrically heated house by 73-79 %. As a result of the renovation work, the annual heating energy consumption of the oil-heated house was reduced by 65 %. The apartment houses were renovated with exterior retrofit insulation and new surface structure for the outside walls. The windows, balcony doors and front doors were renewed. The district heating centre and the heat supply system were modernized. Mechanical supply and exhaust ventilation systems with heat recovery (annual efficiency 30 %) were installed in all apartments. Three apartment houses with varying ages were studied: the original specific heat consumption was from 255 kWh/asm2,a (asm2 = apartment area) to 188 kWh/asm2,a. After the renovation the specific heat consumptions were from 138 kWh/asm2,a to 82 kWh/asm2,a. The cooling energy reduction potential for the office house was examined by dynamic simulation. The power level of the lightning was reduced and the effects of four different solar shading technologies were examined: two solar control glass windows, blinds and awning. Combined with the reduction of the lightning power level, the annual cooling energy use was reduced from 44% to 69 % with solar control glass windows, 56 % with blinds and 71 % with awning.