Guillermo Barrios

There is a worldwide effort aimed at reducing energy consumption in buildings. Part of this effort includes bioclimatic design in the curricula for architects and engineers. The selection of constructive systems for the building envelope according to the climate is of significant importance for bioclimatic design. This has to be done by calculating the heat transfer through the constructive system using the time-dependent model. However, because the time-dependent model is easier to use it is also more commonly employed. To contribute to the teaching of the importance of using the time-dependent model, a didactic device and a practice were proposed. This paper presents the physical problem and the heat transfer models; the didactic device’s design process, its components and operating method; as well as the methodology for the practice. The didactic device and practice were created by the interaction of experts and students who gave their opinions and suggestions during different workshops.

In this work, a methodology for the validation of non air conditioned building thermal simulations is proposed. Having certainty in these simulations can give confidence to building designers on the possibility to avoid the use of mechanical air conditioned systems or to reduce the period of their use, thus increasing the building’s energy efficiency. The main features of the proposed methodology that differentiate it from the previous ones are i) the separation of data inputs which values are known with uncertainty into those that have more influence on indoor air temperature and those with more impact on surface temperatures; ii) to carry out the calibration process in two stages having as comparison variables indoor air temperature in the first stage and adding surface temperatures in the second stage; and iii) to carry out the validation process in different seasonal, occupancy and ventilation conditions. The case study is an office building, simulations are performed in EnergyPlus employing the Airflow Network model for infiltration and ventilation. Quantitative comparisons are made using eight metrics. The results show the advantages of carrying out the second stage of validation proposed in this work. The validation results show that the building model obtained from the calibration process is suitable to simulate the building in different seasonal, occupancy and ventilation conditions, and can be used with certainty to test strategies to improve thermal comfort in the building. For the case study, two strategies are tested showing important reductions in thermal discomfort on occupancy hours during the critical hot season.

Five models to simulate time dependent heat transfer through constructive systems of building walls or roofs with internal air-cavities that are being implemented in whole-building energy simulation programs are evaluated by comparing their predictions with test measurements. The simulations are made using EnergyPlus. Comparisons of simulation and experimental results demonstrate that the equivalent homogeneous layer set (EHLS) model, presented here as Model 4, that considers the two dimensional heat transfer mechanisms of conduction through the solid part, natural convection in the air inside the cavities and radiation between aircavity surfaces, gives the best results. The second best results corresponds to Model 3 that considers all these heat transfer mechanisms but it is only one-dimensional (1D). The results of this model are close to that of Model 4, indicating that in this case of study the heat flows through the framing path and the in-cavity path are similar. The Model 2 that only considers conduction in 2D gives the third best results and the Model 1 that considers conduction but in 1D gives the worst results. Model 5 is generated from Model 3 but suppressing radiation, results indicate that for this case of study radiation has a significant contribution.