Validation and evaluation of total energy use in office buildings: A case study Azra Korjenic ⁎, Thomas Bednar Vienna University of Technology, Institute for Building Construction and Technology, Research Centre of Building Physics and Sound Protection, Karlsplatz 13/206-2, A-1040 Vienna, Austria abstract article info Article history: Accepted 18 January 2012 Available online 14 February 2012 Keywords: Office buildings Total energy performance Dynamic simulation HVAC systems Building occupancy This paper illustrates the concept of using dynamic simulation as an instrument for total energy performance validation and analysis for office buildings and their HVAC systems. The intent is to use simulations to estab- lish performance criteria to evaluate monitored data to validate building performance, analyze energy, and to predict the energy consumption during the planning phase. In this study, the total energy use is examined in a real office building modeled using a dynamic simulation. The very comprehensive measured data about en- ergy consumption for each part of the HVAC systems and appliances were compared with the simulation results. The results of this analysis suggest that very good agreement can be achieved using the available precise input data, especially building occupancy patterns and activities. © 2012 Elsevier B.V. All rights reserved. 1. Introduction There is often a significant discrepancy between calculated and ac- tual total energy consumption in buildings. The deviance from the ini- tial estimation for office buildings can be especially large because the intended building use is unknown in the design phase. Nevertheless, the energy performance of the building is established using calcula- tions during the initial design phase. The reason for the discrepancy from the initial calculation relates more to the combined effect of building operation and maintenance, and occupants' activities and behavior, than with building design and construction. To better un- derstand the determinants of energy use in buildings, an ECBCS pro- ject, ‘Annex 53 [1]: Total Energy Use in Buildings—Analysis and Evaluation Methods’, is currently exploring the impact of building use, operation, and maintenance using statistical analyses. A number of numerical, experimental, and theoretical investigations have been undertaken recently to improve knowledge about the total energy use in buildings (Annex 53), to define the necessary calculation in- puts for simulation, to establish if energy consumption may be pre- dicted, and to select the most appropriate prediction method. The monthly balance method is not suitable for precise whole building calculations as the energy demand is often underestimated in the cal- culations Korjenic et al. [2]. Both short-term predictions and long- term building performance forecasts (50 to 80 years) are increasing in importance and popularity [3]. To achieve satisfactory results, a wide range of scenarios must be simulated with realistic climate sce- narios [4]. Accurate and extensive input data are required for asses- sing existing buildings using dynamic procedures. Unavailable meteorological data and incomplete materials data often hinder the acceptance of modern calculation methods in practice [5]. The building envelope along with the heat losses and gains through the envelope are generally easy to reproduce in a simulation model, but it is difficult to obtain the total energy consumption by HVAC systems. All factors, including building operation, occupants' activities and behaviors, and indoor environmental quality, should to be taken in account using a combination of simulation and real measurements of energy use data. An integrated or whole building design process involves studies of the energy-related impacts and in- teractions of all building components, including the building location, envelope (walls, windows, doors, and roof), HVAC system, lighting, controls, and equipment, indicating the high level of complexity in- volved when seeking the correlation between different systems [6]. In this study, the whole building energy consumption, HVAC, and electrical appliances were noted in detail and reproduced in dynamic simulations. It has been shown that prior knowledge of building use, including all equipment used, is necessary to correctly predict energy consumption and to calculate accurate results. 2. Building description and building systems The case study office building presented in this paper is located in Melk, Lower Austria, Austria. The building was constructed in 2007, and is comprised of a basement with three aboveground storeys. See Fig. 1. The gross heated area of the building is 4811 m 2 . The gross heated volume is 18,099 m³ including offices, meeting rooms, and secondary rooms. The office building is occupied by 129 employees. The offices are situated at the facades. The restrooms, kitchen, small archives, IT room and the staircase are in the core. Offices and primary work areas are heated to 22 °C. The corridors and interior Automation in Construction 23 (2012) 64–70 ⁎ Corresponding author. Tel.: + 43 1 58801 20662. E-mail address: azra.korjenic@tuwien.ac.at (A. Korjenic). 0926-5805/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.autcon.2012.01.001 Contents lists available at SciVerse ScienceDirect Automation in Construction journal homepage: www.elsevier.com/locate/autcon