A new approach to identify achievable nearly-zero energy building targets for existing building retrofits

Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings aims to improve energy performance of buildings since the building sector represents 40% of the energy consumption. Nearly-zero energy building (NZEB) concept was also introduced with this directive called EPBD recast. NZEB is described in EPBD recast as a building with a very high energy performance. It is also expected that the required energy is mainly met by the renewable energy sources. As seen from this definition, a certain energy performance level has not been identified for NZEBs, thus the NZEB level should be identified at national level. The target of the Directive related to NZEBs points at year 2021 as the deadline for ensuring all new buildings are constructed as NZEBs. This requirement directly links the NZEB concept with the cost-optimality concept by expecting that starting from 2021 NZEB level will be the minimum energy performance requirement for buildings. Besides the new buildings, EPBD recast includes NZEB requirements for existing building retrofits as well. Cost-effective transformation of the existing buildings into NZEBs is obliged and correspondingly increasing number of NZEBs is targeted. However, any deadline has not yet been specified for these requirements related to retrofitted NZEBs. This dissertation presents an approach to identify achievable NZEB targets for existing building retrofits. The approach regards the NZEB level as future cost-optimal level and adopts the comparative methodology framework introduced by the European Commission for cost-optimality calculations as the first phase for investigating potential NZEB levels. This phase of the approach extends the cost-optimality calculations by integrating the analyses related to the effect of occupant behaviour on the cost-optimal levels. The second phase offers the sensitivity analyses as the main tool to investigate potential NZEB levels and determine the financial gap between existing cost-optimal levels and the NZEB level. At the end of this phase proposals are prepared for bridging these gaps. Finally, the third phase focus on the national decision making procedure on NZEB definitions. Although the policy-makers are in charge of this phase, this approach proposes a general frame to present the relation between decision-making process and the previous analyses. A sample implementation of the proposed approach is also presented in this dissertation. It was applied on a reference residential building in Turkey. Results obtained from this sample implementation emphasize the necessity of following a comprehensive approach in order to achieve promising cost-optimal levels for building retrofits. Moreover, this implementation displays the significant effect of conscious occupant behaviour on the results and points at the importance of awareness-raising activities for building occupants in terms of achieving improved NZEB levels. The approach proposed in this dissertation provides a whole approach for identifying national targets for retrofitted NZEBs. It brings a new perspective by moving from scientific point of view to enforcement and presents an improved approach by integrating the occupant behaviour effect into the calculations. Moreover, by regarding the sensitivity analyses as the main tool for investigating NZEB levels, the approach is expected to guide further research activities. Through sample implementation, coherence between the obtained results and the European NZEB targets is also demonstrated. This approach also encourages further studies related to cost-optimality and NZEB concepts. The further studies can also be adapt the proposed approach to new buildings in order to be used in periodic assessment and revisions of NZEB definitions. Moreover, the approach can also be exended by integrating thermal comfort related calculations.