The year witnessed the launch of Looking back

The year 2012 witnessed the launch of . Looking back on the past year, to our delight, the original goal is being achieved through the four issues, that is, to publish scientifically and technically sound papers as well as high standard papers dealing with the social aspects of architecture. Therefore, we are confident that the future of this journal is promising. We are looking forward to the efforts and fruits next year, in the hope of making this journal a vibrant platform for rapid communication among international scholars, architects, and engineers.
Introduction Within the European project Climate for Culture, researchers are seeking to find the influence of the changing climate on the built cultural heritage. The Building Physics and Systems group at the University of Technology of Eindhoven participate in this project (Schijndel et al., 2010). Currently they are able to simulate the indoor climate of several monumental buildings for the next hundred years (for results see Kramer, 2011) using the model HAMLab (Schijndel, 2007) with artificial climate data for the years 2000 until 2100. Due to the long simulation AP24534 (hundred years with time step 1h), combined with detailed physical models, the simulation run time is long. Furthermore, the detailed modelling of the buildings itself requires much effort: the monumental buildings are old and protected. Therefore, blueprints are hard to find and destructive methods to obtain building material properties are not allowed. This paper will be very interesting for anyone who wants to know more about simplified building models. Questions are answered like: what kind of modelling approaches are applied? What are their (dis)advantages? What are important modelling aspects? Section 2 gives a brief history. Section 3 deals with simplified building models, with Sections 3.1, 3.2 and 3.3 respectively on neural network models, linear parametric models and RC-models. Finally, Section 4 reviews the topic of inverse modelling.
Building simulation models: a brief history Building simulation models have been developed over many years, starting with very simple models (e.g., Bruckmayer, 1940) which dealt with the analysis of conduction through one building element. These models were completely analytical. Later, in the 1970s and 1980s, research was focused on four approaches which modelled one or more building zones: Sometimes, different approaches are combined. For example, Xu and Wang (2008) use CTF for detailed modelling of the conduction through walls and use a thermal network model (Lumped capacitance model) for the modelling of the rest of the building zone. However, detailed wall properties are necessary to use the CTF approach. Santos and Mendes (2004) use the finite difference method for wall conduction and the lumped capacitance method for the rest of the building zone. The most recent development in research is to achieve a synergy by using several simulators simultaneously (Trčka, 2008), which is referred to as co-simulation. In this way, the strength of different simulators can be combined.
Simplified building models Due to the increase of computational power, the attention for simplified models has decreased. However, through the years community age became clear that simplified models have benefits over complex models (Wang and Chen, 2001; Mathews et al., 1994): user friendliness, straight forward, and fast calculation. Neural network models (e.g., Mustafaraj et al., 2011) can be classified as black box models. The parameters have no direct physical meaning, but the output is generated by the hidden layers (black box) from the input. Some models are referred to as grey box models. An example in the field of simplified building models is the use of linear parametric models (Mustafaraj et al., 2010). The linear model itself is a black box model, but the parameters can be determined using physical data (Jimenez et al., 2008). Some researchers stress out the importance of simplified models with physical meaning (Kopecký, 2011), so called white box models. The lumped capacitance model can be classified as a white box model. Another advantage of this approach is the representation of building elements using R (resistance) and C (capacitance), according to the electrical analogy, which makes a graphical representation of the model possible. Most of the simplified building models are based on this approach.