Impact of Local Urban Climate on Building Energy Performance: Case Studies in Mendoza, Argentina

Abstract

Building thermal performance and its energy consumption are affected by the energy exchange processes taking place between the outer skin or envelope of the building and the surrounding environment. It is a dynamic system in which there are continuous changes in a daily and seasonal range. Quantity and quality of the exposed envelope as well as albedo, vegetation and urban geometry are significant factors in determining the impact of urban microclimates on energy building consumption. Existing buildings and their microclimates can be monitored in situ. This practice is very useful but time and resource consuming. Only some punctual cases can be evaluated thoroughly, and it is impossible to measure buildings that are still in project. Building Energy Simulation (BES) programmes are capable of modelling building energy performance in detail in a dynamic model. The weather variables in an urban microclimate may be subtly different from the conditions prevailing over the area as a whole. Nevertheless, the input of meteorological conditions is usually taken from long-term averages provided by local weather stations. These data series ignore the modifying effect on the surroundings. This chapter presents a case study in a high density area in the city of Mendoza, Argentina in which year round in situ measurements of temperature, humidity, radiation and air movement were taken in two different scales: within the streets in a neighbourhood and outside and inside a building. The micro-urban scale and the building scale were covered. A specific weather file was created for each scale, to be integrated in simulation software ENVI-met and Energy Plus respectively. Models were calibrated with the monitored data, to be run again with the information provided by local weather stations. Also, as a third term of comparison, the simulation workflow moves from the micro-urban to a building scale assessment by linking the ENVI-met software micro-climatic results to the building energy simulation program Energy Plus. Results obtained a)with the local weather stations average climate input, b)with the onsite microclimatic measurements and c)with ENVI-met software are compared in order to asses each case reliability in assessing the impact of local urban climate on building energy performance. Simulated ? monitored results present differences of +/- 3.5%. This study reveals the capabilities and advantages of working with this tool for the generation of microclimatic data, which integrated with Energy Plus, presents a less expensive and fast alternative to in situ monitoring.