<p>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.</p><p>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.</p><p>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.</p><p>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.</p>

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.

Residential and public buildings account for about 40% of the annual energy use in Europe. Many buildings are in urgent need of renovation, and reductions in energy demand in the built environment are of high importance in both Europe and Sweden. Building energy simulation (BES) tools are often used to predict building performance. However, it can be a challenge to create a reliable BES model that predicts the real building performance accurately. BES modelling is always associated with uncertainties, and modelling occupancy behaviour is a challenging task. This research presents a case study of a BES model of a school building from the 1960s in Gävle, Sweden, comprising an example of a validation strategy and a study of energy use and potential energy-efficiency measures (EEMs). The results show that collection of input data based on evidence, stepwise validation (for unoccupied and occupied cases), and the use of a backcasting method (which predicts varying occupancy behaviour and airing) is an appropriate strategy to create a reliable BES model of the studied school building. Several field measurements and data logging in the building management system were executed, in order to collect input data and for validation of the predicted results. Through the stepwise validation, the building’s technical and thermal performance was validated during an unoccupied period. The backcasting method demonstrates a strategy on how to predict the effect of the varying occupancy behaviour and airing activities in the school building, based on comparisons of BES model predictions and field measurement data. After applying the backcasting method to the model, it was validated during an occupied period. The annual predicted specific energy use was 73 kWh/m2 for heating of the studied building. The distribution of heat losses indicates that the best potential EEMs are changing to efficient windows, additional insulation of the external walls, improved envelope airtightness and new controls of the mechanical ventilation system. / Byggnadssektorn står för ungefär 40 % av den årliga energianvändningen i Europa. Många byggnader är i stort behov av renovering och en minskning av energibehovet inom den byggda miljön är av stor vikt i både Europa och Sverige. För att undersöka byggnaders energianvändning används ofta simuleringsverktyg, men det kan vara utmanande att skapa pålitliga simuleringsmodeller som tillräckligt noggrant predikterar den verkliga byggnadens energianvändning. Simulering av byggnaders energianvändning är alltid förknippat med osäkerheter och att simulera människors beteendemönster är en stor utmaning. Den här forskningen innefattar en fallstudie med en simuleringsmodell av en skolbyggnad, byggd under 1960 talet och belägen i Gävle, inkluderat ett exempel på en valideringsstrategi och en studie av energianvändning och potentiella energieffektiviseringsåtgärder i byggnaden. Resultaten visar att insamling av indata baserade på evidens, stegvis validering (obemannad och bemannad) och användande av en backcasting-metod (vilket predikterar varierande brukarbeteende och vädring) är en lämplig strategi för att skapa en pålitlig energisimuleringsmodell för den studerade skolbyggnaden. Flertalet fältmätningar genomfördes och data loggades i systemet för fastighetsautomation, för att samla indata och för validering av de predikterade resultaten. Genom den stegvisa valideringen kunde byggnadens tekniska och termiska prestanda valideras för en obemannad period. Backcasting-metoden visar en strategi för hur man kan prediktera varierande brukarbeteende och vädringsaktiviteter i skolbyggnaden, baserat på jämförelser av modellens prediktioner och data från fältmätningar. När backcasting-metoden tillämpats i energisimuleringsmodellen, kunde modellen valideras för en bemannad period. Den årliga predikterade specifika energianvändningen för uppvärmningen är 73 kWh/m2. Fördelningen av värmeförluster i byggnaden indikerar att de bästa potentiella energieffektiviseringsåtgärderna är byte till fönster med bättre U-värde, tilläggsisolering av ytterväggarna, bättre lufttäthet i byggnadsskalet och ny styrning av det mekaniska ventilationssystemet.