Modelling relationship among energy demand, climate and office building features: A cluster analysis at European level

More than one-third of the energy demand of industrialised countries is due to achieving acceptable conditions of thermal comfort and lighting in buildings. Energy demand in buildings depends on a combination of several parameters, such as climate, envelope typologies, occupant behaviour, and intended use. Indeed, assessing a building's energy performance requires substantial input data describing constructions, environmental conditions, envelope thermo-physical properties, geometry, control strategies, and several other parameters. This has been a very active area of research in recent years, and several numerical approaches have been developed for building simulation; furthermore, most of these approaches have been tested and implemented in specialised software tools. However, the use of these tools poses many challenges in regards to the retrieval of reliable and detailed information, setting a steep learning curve for engineers and energy managers. It is often more convenient to have a simplified model that allows the evaluation of energy demand with a good level of accuracy and without excessive computational costs or user expertise. In this work, the authors extrapolate a set of simple correlations to permit a fast preliminary assessment of heating energy demand for office buildings. Data employed to build the correlations come from detailed dynamic simulations performed in TRNSYS environment. The models were built according to the standards and laws of building energy requirements in seven different European countries. For a more general assessment, the authors identified three cities for each country; for each location, three models with different shape factors were considered (S/V = 0.24, 0.5 and 0.9). The results obtained from the simulations allowed for the determination of direct correlations among the thermal energy demand for space heating HDD and S/V values. In this way, the authors provided simple equations for a reliable and easy-to-use preliminary assessment of the energy demand of non-residential buildings to planners and designers, taking into account regulation dictated by law in each considered country.