Energy efficiency improvements of a school building from the 1960s in Hållsta, Eskilstuna

In June 2006 the Swedish government decided that the use of energy in buildings should be reduced by 20 percent until 2020, compared to the level of energy used in 1995. To contribute to this goal, the real estate company “Eskilstuna Kommunfastigheter AB”, set up own goals for their buildings. In 2009, the goal for schools was to have a maximum energy use of 118 kWh/m2year for heating and hot water. The school “Hållsta skola”, just south of Eskilstuna, exceeds the limit since it used 270 kWh in 2008. The school is heated by oil burners, which is not desirable since oil is a fossil fuel. The aim of this study was to identify cost effective measures for decreased energy use for heating and hot water in the school, and to find alternatives to the oil burners. The school was built between 1963 and 1975 and consists of two buildings. The insulation in the roof, walls, windows and floor is poor and the ventilation is mainly performed without heat recovery. Measures including insulation of the roof, new windows, heat recovery in the ventilation system and more effective water taps were studied with Life Cycle Cost analysis (LCC) and Pay-off analysis. The energy use with and without the new performance was calculated with the building simulation program VIP+. If all of the economically favorable measures are carried out the total energy use would decrease to 167 kWh/m2year. One of the alternatives to oil burners that were suggested is heat pumps. The two types of heat pumps studied, ground source or air source, were both found to be profitable, although the ground source heat pump would be slightly more profitable. In the calculations it was considered that an electric boiler would back up the heat pumps during cold days. With heat pumps, the energy bought for heating and hot water would be about 55 kWh/m2year, which is well below the goal of maximum 118 kWh/m2year