**Preface to "Probabilistic and Fuzzy Approaches for Estimating the Life Cycle Costs of Buildings"**

The construction sector is a major consumer of natural resources and incurs high costs. Life cycle cost (LCC) makes it possible for the whole life performance of buildings and other structures to be optimized. The introduction of the idea of thinking in terms of a building life cycle resulted in the need to use appropriate tools and techniques to assess and analyze costs throughout the life cycle of a building. Traditionally, estimates of LCC have been calculated based on the historical analysis of data and have used deterministic models. The concepts of probability theory can also be applied to life cycle costing, treating the costs and timings as a stochastic process. If any subjectivity is introduced to the estimates, then the uncertainty cannot be handled using probability theory alone. The theory of fuzzy sets is a valuable tool for handling such uncertainties.

In this Special Issue, a collection of 11 contributions provide an updated overview of the approaches for estimating the life cycle cost of buildings. In the first paper the importance of information and communication technology use in life cycle cost management are considered. The research assumes that the most critical implementation factor is the investment cost. The second paper uses multiple criteria analysis to define the factors influencing the sustainable construction industries in the EU member states, the UK and Norway. Construction development of Commercial and Recreational Complex Building Projects (CRCBPs) is one of the community needs, but the implementation of these projects is usually very costly. The results and findings of the third article can be considered by CRCBPs in both the private and public sectors for properly effective risk identification, evaluation, and mitigation. The next four papers (4–7) consider the broadly understood maintenance phase of the building, with particular emphasis on the costs incurred at this stage. The eighth article deals with the partial outputs of large-scale infrastructure project risk assessment, specifically in the field of road and motorway construction. A partial section of the research was focused on the analysis of the probability distribution of the input variables, especially "the investment costs". The research topic of the ninth article addresses a part of the evaluation of railway infrastructure project efficiency within its life cycle by using the cost–benefit analysis method. The contractor selection problem, with emphasis on the life cycle costing method as the criterion of choosing the most appropriate company, is discussed in the tenth paper. In the last article, the parameters of tuned mass dampers are optimized to improve the performance level of steel structures during earthquakes.

> **Edyta Plebankiewicz** *Editor*
