Hygrothermal Simulation of Buildings: A Study on the Different Types of Weather Files

One of the major factors impacting the hygrothermal study of buildings using numerical simulation tools is the local weather at the building's location. Usually, this weather is defined in a climate data file that refers to a weather representative year for the site under consideration. Numerical simulation tools such as Energy Plus or WUFI Plus, among others, have their own database of weather files representing different locations, but for studies in more specific locations or for model validation, these databases may not provide the desired weather files and/or these files are missing several important climate data parameters (e.g., relative humidity, wind, radiation, rain, etc.), making it difficult to adequately characterize the climate where the numerical simulation is to be performed. In this sense, in most studies it is necessary to create personalized climate files to have control over the climate data to be used in the simulation. The aim of this study is to evaluate the types of weather data available, the mathematical methods used to generate them, and the types of climate parameters involved. To this end, the statistical accuracy between climate variables obtained from international climate databases and those obtained from a national database was evaluated. The climate file created as part of this study allowed to measure with greater accuracy the climate parameters, the mathematical methods used to create weather files, and the type of climate data to use as input in each hygrothermal analysis program. The climate is hourly defined in a climatic file representing a year that is representative of the location to be studied. Subsequently, applying the climatic file to analyze the hygrothermal performance of a model designed with a wall construction solution representing most buildings in the Portuguese building stock will be assessed. Firstly, a review was conducted on the types of climatic files available, the mathematical methods applied, the types of climatic variables needed to create them and the best method to create the climatic file. The software used for the analyses will be WUFI Plus, which operates based on certain climatic variables obtained from international and national climatic databases. After the review, a decision was made on the type of climatic file and method to use for creation. Finally, the climatic file chosen to be created was a Moisture Reference year. Afterwards, a validation by statistical indices and visual comparation of the values obtained from in situ measurements and satellite measurements was made, concluding that the best values were found to be from temperature, relative humidity and global radiation. The years to be the Moisture Reference Year were selected using a Moisture Index (MI) approach, and afterwards the file was used as input for analyzing the hygrothermal performance.