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Planning and Scheduling tools used by construction professionals nowadays not always consider the effect of variability in the construction process; they do not consider explicitly the effect of changes in activity durations along the production chain. Discrete event simulation approach is a relevant exception that deserves particular attention from the construction industry. The present research proposes a discrete event simulation model applied to a simplified construction process schedule. This model considered main construction activities divided in: foundations, structure and roofing. The model can be extended and easily applied to other construction activities. Input parameters for the model were obtained directly from on-site field experience and a beta unimodal distribution assigned. On a first stage, PERT scheduling methodology was used for the model, which was later compared with discrete event simulation. Results did not provide evidence of significant statistical differences between different probability distribution used with respect to the mean project duration obtained using PERT scheduling as compared to the discrete event simulation model. This provides conclusions about total project duration and validation of the probability distribution types considered in the present research.

The current depletion of fossil fuels and environmental degradation are requiring greater energy efficiency in buildings, particularly in the residential sector. However, environmental improvement actions for dwellings are usually based on general considerations, without identifying the most appropriate measurements to be taken in each case, or reviewing their application with stakeholders. This article puts forward a strategy to propose effective and feasible modifications in the design or refurbishment of single-family homes to reduce energy use while maintaining indoor comfort. The improvements proposed are based on dynamic energy simulations of individual models adapted to local realities that can be carried out by regular professionals. The process includes the review of studies and information on the geographic area, and compilation of the constructive features and occupancy data of each house to create a proper energy behaviour model. Possible improvements to the building are then simulated separately in each model and the results recorded. Subsequently, a budgetary analysis of these alternatives according to construction costs and financial projections is carried out in order to identify retrofit packages and consult the opinions of residents and builders. The application of this strategy is demonstrated in the study of several houses in Concepción, Chile, where different sets of measures have been identified to achieve high reductions in energy demand while having low cost and being highly appreciated by the participants. This provides a methodology for developing and validating effective solutions for the environmental improvement of existing dwellings and new housing projects.

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