Evaluation of the quasi-steady-state method for the assessment of energy use in school buildings

Since the implementation of the European Directive 2002/91/EC on the Energy Performance of Buildings the number of very low energy and passive non-residential buildings has increased significantly. In Flanders (Belgium), the evolution towards more energy efficient schools in particular was encouraged by the approval and subsidizing of 24 passive pilot schools. Steady-state calculation tools source are generally used for the energy performance compliance checking in a regulatory context. Reliability and accuracy of these assessment results, which depend both on the representability of the standardized input data and on the method itself, are crucial to ensure the effectiveness of the building energy policy. Therefore, in this framework, the aim of the study is: (i) a large scale analysis and description of the typical characteristics of the Flemish school building stock, (ii) the impact of these characteristics on the energy consumption and consequently the translation of the effects in the quasi steady-state calculation method used for energy performance evaluation and (iii) analysis of the influence of the proposed changes of the calculation method on cost optimal school design. The first phase includes the analysis of the typical characteristics of school buildings and the determination of a state-of-the-art of the applied techniques and systems in schools. Based on these results, abstracted school type models are then defined, which, in combination with parameterization of wide-ranging construction and activity related characteristics, represent the current school building stock. In a second phase, the impact of the specific school building properties on the energy consumption is determined and improvements of the calculation methods are suggested based on parallel national and international optimization projects. A set of representative boundary conditions is defined which can be used, directly, for dynamic simulations or can be converted into monthly averaged input data for the simplified calculation methods. Next, the accuracy of the monthly calculation method itself - and more in particular the implementation of dynamic effects - is modified to the use of school buildings. The utilization factors for the heating and cooling balance are adapted and the impact of intermittency on the energy demand is studied and evaluated through a comparative analysis of the various quasi steady-state calculation methods. Finally, integrated dynamic simulations including both building and HVAC and building are used to assess primary energy use for heating, cooling, ventilation and related auxiliary energy. As a final step, the impact of the aforementioned study results on the determination of the cost-optimal solutions for schools is studied.status: publishe