12th International Symposium on District Heating and Cooling

The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, EstoniaThe results show that the period 1965–1974 did nothave a dramatically higher heat use in the constructionyear analysis.3. Degree daysThe climate in Sweden varies with a much colderclimate in the northern part compared to the southernpart. Since the statistical data consist of buildings fromdifferent parts of Sweden, the influence of the localclimate on the heat use in buildings can be analysed.This has been done by analysing the correlationbetween the number of degree days for the location ofa building and the corresponding specific heat use.The number of degree days, according to the Swedishdefinition, varies from approximately 3000 in the southup to 7000 in the north of Sweden. Each building in theanalysis was connected to one of 14 climate areas.Heat usekWh/m 2400350300in the theoretical analysis of the optimal wall insulationas a function of degree-days.The results show that the average difference betweenNorthern and Southern Sweden was small, implying asmall climatic impact on heat use. The main conclusionfrom this analysis is that the individual variation in eachclimate area is much higher than the local impact ofclimate. This astonishing conclusion can have severaldifferent explanations:Higher awareness and consequences of lowbuilding heat resistances in Northern SwedenLower regional GDP in Northern Sweden givinghigher incentive to reduce heat costsMore frequent snow cover in Northern Swedengiving extra heat resistance during the winter.4. Energy efficiency measures.The statistical data shows the energy efficiencymeasures during the period 1995–2005. The energyefficiencymeasures were:a. Supplementary insulation250200150100y = 15,63x 0,28b. More energy efficient windowsc. Balancing heating- and ventilation systemsd. Electrical efficiency measures5002000 2500 3000 3500 4000 4500 5000Degree-daysFig. 6 Specific heat use for 5111 multi-family buildings asa function of the number degree days in each climatearea.Heat usekWh/m 240035030025020015010050y = 10,37x 0,3002000 2500 3000 3500 4000 4500 5000Number of degree-daysFig. 7 Specific heat use for 6041 service buildings as afunction of degree days in each climate area.Fig. 6 and Fig. 7 show the specific heat use as afunction of degree days for multi-family buildings andservice sector premises. The figures also show theaverage curve and its equation for specific heat use asa function of degree-days. You should also note thatthe exponent in the fitted equations has only themagnitude of 0.3 instead of the 0.5 exponent obtainede. Heat recovery in ventilation systemsIn multi-family buildings, one or several energyefficiency measures were implemented for anestimated floor area of 57.6 million square metresduring the period 1995–2005. No energy efficiencymeasures had been performed for an estimated floorarea of 92.2 million square metres during the sameperiod.In service sector premises, with an estimated floor areaof 37.2 million square metres, one or several measureshad been taken during the period 1995-2005. Duringthe same period, no measures had been taken for anestimated floor area of 70.3 million square metres.The most common measures in multi-family buildingsand service sector premises were balancing of heatingandventilation systems.In many buildings, a combination of two or severalenergy efficiency measures had been taken in thesame building. In some buildings, up to five measureshave been taken in the same building.The average heat use in multi-family buildings andservice sector premises in relation to measures takenis shown by bars in Fig. 8 and Fig. 9. The horizontallines show the average heat use in buildings, in whichno energy efficiency measure was performed.275