An Investigation of Cost-Efficient Solutions in Order to Meet the Energy Requirements in Multi-Family Buildings

Abstract: As the requirement for specific energy usage is tightened it becomes more important to ensure that the most cost-efficient combinations of energy saving measures are presented. This master thesis have been developed based on one main research question and two sub-questions; How can MOBO and IDA ICE be utilized to identify cost-efficient combinations of energy saving measures to meet tightened requirements for specific energy usage?; Which parameters are included in such an utilization?; and How can the number of interesting data points be decreased so that the most appropriate solution is found?. In order to answer the questions MOBO and IDA ICE have been utilized by varying different windows, the amount of insulation in external floors and roofs as well as different air handling units can be varied simultaneously. Thus the most cost-efficient combinations of energy saving measures can be obtained through a systematic approach. Furthermore a cost-efficiency analysis has been made for installation of waste water heat exchanger, solar PVs and a pre-heating system for ventilation air. The cost-efficiency analysis is made from a basis of a tightened requirement of specific energy usage by 30 %.The results have been obtained by utilizing MOBO in combination with IDA ICE. By a large number of simulations through MOBO on four case studies the most cost-efficient combination of energy saving measures is presented. By simulations on different case studies it was shown that the shape of the Pareto fronts are similar. The results show that it is important to set the initial conditions of a building so that it is possible to reach tightened requirements for specific energy usage. In case the initial conditions are poor it can be seen that the requirement cannot be met cost-efficient since the number of energy saving measures are large and the relative investment cost increases rapidly.The conclusion of the main research question is that MOBO could be used in an early stage of the development process so that the initial conditions can be set in such a way that the tightened requirements for specific energy usage can be met cost-efficient. Cost-efficient combinations of energy saving measures can be identified by utilizing MOBO in combination with IDA ICE. Furthermore, energy saving measures that result in a significant energy saving to a relatively small additional investment cost can be found. Lastly, by utilizing MOBO new technical platforms can be developed with a systematic approach.The conclusion of the first sub-question is that the following parameters are included; three different AHUs, three different window resources with different u-values, two different external walls, three different amount of additional insulation in the roof and two different amount of insulation in the external floor. Furthermore, the results obtained by utilizing MOBO and IDA ICE can be combined by installations of WWHex and solar PVs in case it is cost-efficient. An additional analysis should be made for each case.The conclusion of the last sub-question is that the number of interesting data point can be reduced by only use the Pareto front. In addition a tightened requirement of specific energy usage in combination with a budget requirement results in only a few appropriate combinations of energy saving measures.