*2.2. Climatic Zoning Development*

Weather files are an important element for energy simulation because of their influence on the building energy performance results. The article entitled Impact Assessment of Building Energy Models Using Observed vs. Third-Party Weather Data Sets clarified that: "The sensitivity analysis of the main weather parameters showed the different influence that each parameter had on the energy demand variation of each test site". In this regard, the relative humidity and wind direction had little influence on the models; the two parameters with the strongest influence on the models were wind speed and temperature [14]. The variations in elemental climatic characteristics result in different thermal envelope behaviors. Then, the importance of having a classification of different climatic zones, with their corresponding weather reference values, becomes a reason for considering climatic zoning. There are some examples of how weather conditions and climate affect the thermal envelope and HVAC system performance. Hang et al. explained the importance of considering weather statistics for improving the energy performance of HVAC systems. They tested an HVAC system control with the new set-point temperatures calculated from the derived equation, improving thermal comfort by 38.5%. This study confirmed that a cooling set-point temperature that considers both the thermal characteristics of a building and the weather conditions effectively enhances the indoor thermal comfort during summer. They also noted the need for a continuous update of the existing hourly weather data files that are used in dynamic simulations or for the prediction of the peak thermal loads of buildings, as they affect the capacity of HVAC equipment to respond to current climate change [15,16].

Why does climatic zoning need to be developed for Mexico? The only available zoning was developed by the Institute of Geography of the Mexican Autonomous University (UNAM) in 2005. In the introduction, we explained how they delimited the zones. To delimit the domains with potentially similar climates, a regionalization was proposed based on the country's orography, hydrology, and elevation. Figure 2, for example, explains the relationship between cities elevation and their climatic characteristics (higher elevations are associated with cold weather, and lower elevations with warm weather). The geographical characteristics of rainfall, humidity, and temperature change even between short distances. As a consequence, a wide diversity of climates is created [17]. This zoning classifies the national territory into eleven zones. Each of these zones was determined by the study of several factors: dominant winds, rainfall patterns, annual temperature records, thermal annual oscillations, relative humidity, and average temperature rates. There are similarities between different climatic zones. For example, the states located on the coast line of the Pacific Ocean (Guerrero, Jalisco, Michoacán, and Oaxaca) present iso-thermal climates, meaning they have a thermal oscillation of 5 ◦C or less throughout the year.

The impact of climate change and warming on the climatic characteristics of Mexico must be highlighted. Liberman and O'Brien explained how climate change produces variations in moisture, rainfall, and mean temperatures. By analyzing the regional impacts of global warming in the country, the results always tend to be warmer and drier. Whichever model is used, it seems that potential evaporation will increase, and, in most cases, moisture availability will decrease, even where the models project an increase in precipitation. Owing to the effects of global warming, the temperature, moisture and humidity data have variances over time [18]. From this statement, weather data and climatic files are necessary for obtaining more accurate energy simulations.
