*2.4. Traditional Construction Systems*

For the third aim of the methodology, we researched the main traditional construction systems in Mexico. This included official information sources, like the Home Survey of the National Geography and Statistics Institute (INEGI) [27], and two scholarly publications about construction systems used in Latin American countries [8,28]. Each year, INEGI publishes the results obtained from an annual population census. Among the different result categories listed, one is focused on housing. The systems listed on the report were studied, and we compiled a list of those most used in the country. The listed systems were divided by the building elements to which they are applied (roof, walls, or ground), and the principal material present in their component elements.

As shown in Figure 6, the principal materials used in Mexican traditional construction systems were determined. For the construction of ceilings, the principal material used is concrete slab or joist and beams slab, with a 70% incidence. The second most popular material for ceilings is metallic sheet with a 16% incidence, followed by wood at 4% [27]. For the construction of floors, the principal material used is concrete slab, at 55% incidence, followed by covering (wood and mosaic) at 53% and pure soil at 3% [27]. For the construction of walls, the principal material used is fabrics (brick, block, stone, and partition) at an 85% incidence, followed by adobe (vernacular technique with mud and straw) at 9% and wood at 5% [27]. The survey results showed that the main construction system used in Mexican buildings is reinforced concrete with an incidence between 55% and 85% for all components). Mexican constructors used local vernacular techniques inherited by their ancestors, like adobe and bahareque (construction technique that uses adobe, straw, bamboo, and metal or fiber cement sheets for walls).

**Figure 6.** The principal materials used in Mexican housing grouped by building components (walls, ceiling, and floor). A total of 73,405 houses were considered by the National Survey of Housing and Population, National Institute of Statistics and Geography (INEGI) 2018.

> By analyzing the results, two undesirable practices were denoted. First is the use of fiber–cement in construction. This material contains asbestos. Constant asbestos exposure poses serious human health risks for diseases, like lung cancer, asbestosis, and mesothe

lioma. It is not dangerous when packed or sealed in elements, like tiles, panels, or cabinet tops, but they are hazardous when those elements are in bad condition and the interior material is not sealed (resulting in the release of asbestos fiber in the air). Asbestos is forbidden in the majority of world construction standards due to its dangerous effects [29]. Knowing its hazardous characteristics, the common use of fiber–cement materials in Mexican housing is unsafe. Notably, many houses do not have floors, using the local soil (3%). In Mexico, almost 14 million houses do not meet the minimum acceptable conditions for a comfortable house due to the dirt floor and lack of access to quality water supply and sanitation services. In Mexico, 2 of 10 citizens lack access to one public service in their homes [30]. This is an opportunity for improving social housing conditions; improving energy performance and internal comfort with affordable materials could contribute to this improvement.

From each of the construction systems, we broke down the component elements, listing the different material layers' compositions. Finally, the four main characteristics of every material listed in the catalogue (layer width, conductivity coefficient, density, and measure unit) were researched and reported. With all the data compiled, the final construction system catalogue was completed.
