Proceedings of the 28th EnviroInfo 2014 Conference, Oldenburg, Germany September 10-12, 2014 1 Multi-Actor Urban Energy Planning Support: Building refurbishment & Building-integrated Solar PV Najd Ouhajjou 1 , Wolfgang Loibl 1 , Stefan Fenz 2 , A Min Tjoa 2 Abstract Considering the large amount of energy consumption in cities, two-thirds of the overall consumption, these latter have an important potential in terms of CO 2 emissions reduction. Therefore, energy strategies are needed at a city level and consequently, adequate planning tools are required to support urban energy planners in assessing their decisions (e.g. which buildings are the best to refurbish). This paper presents an ontology based approach for urban energy planning support applied to building refurbishment and building-integrated solar PV planning. The adopted methodology is an iterative, incremental process, where each iteration leads to the integration of a new planning decision. The process starts by the identification of the actors whose interests are affected by the decision, then developing/ re-using computation models that provide answers for their questions. The different models are integrated using an ontology that models the parts of the city within the scope of the questions to be answered. The system is applied in a district (about 1200 buildings) in the city of Vienna. The adopted approach provides different actors with specific information to their points of view. Furthermore, the output is aggregated to a common level of abstraction, to be understood by all the actors. This approach is applicable to different cities, as the ontology also integrates extension and upgrade mechanisms that provide flexibility to cope with different data-availability contexts. 1. Introduction More than two-thirds of primary energy in the world is consumed in urban settlements [1]. This energy consumption results in approximately 71% of all energy-related direct greenhouse gas (GHG) emissions [2]. Therefore, cities represent a rich ground for taking action to reduce the amount of GHG emissions. Therefore, decision makers, namely city administrations and governments, are developing strategies for energy planning at various spatial scales that clearly state what measures to be taken, where and in what quantities and in which time horizons. However, cities are complex systems regarding the amount of components and interactions they comprise. The components the city covers can be: (i) physical components, such as buildings, streets, facilities, etc. (ii) human components, whose interests are to be considered or even (iii) regulations and laws that regulate the city. All these components, as well as their interactions, are to be taken into consideration by the decision makers in order to develop energy strategies. Moreover, these energy strategies have to be integrated, considering the impact of each decision on other decisions, besides their impact on the city. To cope with the complexity of cities, adequate planning support systems are needed to formalize this complexity and automate the interactions that cannot be handled manually, by urban energy planners. This paper presents an ontology-based approach for urban energy planning support. The ontology comprises information and knowledge to support an urban energy planning process that deals with both solar PV and building refurbishment planning, answering questions such as: what locations 1 AIT Austrian Institute of Technology, Vienna, Austria, {najd.ouhajjou.fl, wolfgang.loibl}@ait.ac.at Energy Department 2 Vienna University of Technology, Vienna, Austria, stefan.fenz@tuwien.ac.at, amin@ifs.tuwien.ac.at Institute of Software Technology and Interactive Systems