Building Energy Efficiency Measures in District Heating Systems

Abstract: Improving energy performance of existing buildings is an important part in decreasing energy use and in turn reducing greenhouse gas emissions and primary energy use. To be able to evaluate how energy refurbishment influences greenhouse gas emissions and primary energy use a wider system perspective is needed which puts the building in its context. This thesis deals with energy efficiency refurbishment performed on multi-family buildings within district heated areas and how greenhouse gas emissions and primary energy use is influenced. Both energy demand and temperature levels are considered.A simulated building is used to evaluate energy refurbishment packages. The results are used as input data for models of district heating systems to cost optimize district heating production. One district heating system model is also used to evaluate the impact of lowered district heating supply temperatures. The results from the cost optimizations are used to evaluate the impact on greenhouse gas emissions and primary energy use.The results show that all refurbishment packages decreases greenhouse gas emissions and primary energy use, but to a different extent. Depending on the fuel types used and to which extent electricity is co-produced in the district heating system, the results of implementing the refurbishment packages vary. The largest reduction of greenhouse gas emissions and primary energy use occurs in a district heating system with a high share of biofuel and no electricity production. Another result is that the temperature levels of a building’s heating system can be reduced when refurbished which promotes low-temperature district heating. The results also indicates that greenhouse gas emissions and primary energy use can be decreased from a short- and medium term perspective if the supply temperature of a district heating system is lowered. From a long term perspective primary energy use is still decreased while greenhouse gas emissions are increased.