Improving energy efficiency in buildings is a major priority and challenge worldwide, as the available measures vary in nature, and the involved decision analyst, who is usually an architect, engineer, or building expert, faces a complex decision problem. The complexity arises from the numerous decision variables involved, which reflect the alternative measures available, and the multiple, usually competitive objectives, in terms of cost, energy consumption, environmental concerns, etc., of the respective decision maker, who is usually the user, occupant, and/or owner of the building.

Such decision-making problems are addressed through some form of modelling, which may be undertaken in various, more, or less complex, ways. It is, however, considered extremely useful, to adopt modelling approaches that aggregate the objectives in a way that leads to specific problem solutions rather than a set of non-dominated solutions (i.e. a Pareto set), which are then presented to the decision maker, to choose the one that is the most satisfactory based on his/her own preferences and value system. To this end, the modelling approach should be able to incorporate the preferences of the decision maker with respect to the decision objectives under consideration, which is a challenge in itself, while raising at the same time the challenge of eliciting these preferences.

The above challenges were addressed by integrating a mixed-integer nonlinear mathematical programming model with the UTASTAR value elicitation method under an interactive decision-making framework. The proposed framework facilitates the decision-making process, so that decisions are made that conform to the value system of the decision maker, without this system having to be prescribed in advance.

To examine the feasibility and efficiency of the integrated decision-making approach, a building is examined under realistic operating conditions. The study confirms the feasibility and efficiency of the approach, demonstrates its functionality, exploits its qualities, and highlights its strengths, weaknesses and limitations.