The rural housing located in the highlands of the Andes, such as the Mesoandean and Altoandean zones in the department of Puno, Peru, corresponding to bioclimatic zones 4 and 5 according to Peruvian Norm EM.110 (1), is characterized by recurrent energy poverty inside the homes, which leads to health problems for its occupants (2). Heating the home can be difficult and costly, particularly for those on low incomes (3). The outdoor temperatures in the aforementioned zones drop below 0 °C due to a recurring climatic phenomenon called “frost” (4). This phenomenon has an impact on housing because it lacks thermal protection in its envelope, and over time has lost its vernacular legacy that involved insulated roofs with Ichu, a local abundant straw. The housing has adobe walls and makes massive use of metal coverings commonly known as “calamina”, which significantly raises indoor temperatures during the day, but that gain is quickly lost in the early hours of the night (5). This change worsens the thermal performance of rural houses. Field measurements during the coldest months showed indoor temperatures around 0 °C at night (6). Considering that for this type of single-story housing, the greatest thermo-energy losses occur in the following order: through the roof, walls, and air infiltration through carpentry (7). The roofs assume the true protagonist in the formation of interior space at the thermal level (8, 9). It is necessary to give importance to materials that allow for the conservation of the heat gained during the day and to conserve it at night (10). In addition, they should avoid large thermal fluctuations when the occupants spend most of their time inside.

Currently, there are a large number of conventional materials used as thermal and acoustic insulation in buildings, with high energy consumption in their processing and problems of reuse that affect the environment. This is due to the requirements of standardization and acceleration of the building process, which often ignores local reality in international architecture. In the context of civil construction, natural fibers could be explored to allow architecture a more sustainable future (11). Nowadays, the use of natural materials and incorporation of plant fibers in the production of numerous systems is intensifying. By using compounds in construction that can be used as sustainable and low-cost substitutes (12).

Lake Titicaca, located in Peru, South America, offers a valuable resource in the form of totora. This plant is a potential insulation material that compares favorably with industrialized and commercialized thermal insulators. It is a highly sustainable and low-cost alternative, capable of greatly improving energy efficiency in areas close to its growth or cultivation (13-15). Several traditional communities, such as those near Lake San Pablo in Ecuador or the Uros in Lake Titicaca, have used this plant for a long time, and some still use it today (16). The Titicaca National Reserve (TNR) has approximately 16,058.62 hectares of totora beds (17). Currently, there is a waste and burning of totora during the dry season, mainly in the months of september and october, caused by communities located along the lake’s shore. They burn the mature and dry stems to obtain tender regrowth, which constitutes a problem and a threat to the local ecosystem (18).

Studies carried out in extremely cold regions of the Peruvian highlands, based on the conception of passive strategies and the almost exclusive use of local and natural materials such as totora, gypsum and adobe in the building envelope, allowed for an increase in the indoor temperature of multi-use spaces in rural households (5, 19). Therefore, these materials are presented as potential solutions in the area.

The objective of the study is to evaluate the physical properties of moisture, absorption, density, durability against fungus, thermal and acoustic insulation, fire resistance, and impact resistance of the combined material of totora and gypsum applied in the ceiling of typical rural houses in the department of Puno.

A characterization of the main raw materials used in the present study was conducted. We have the totora and gypsum. The “totora” is an erect herbaceous plant that grows in flooded areas, streams, wetlands, and sandy areas, belonging to the Juncaceae family (13). In the available literature, according to the Word Checklist of Selected Plant Families (WCSP), it has been identified with different taxa, such as Scirpus californicus var. Tatora (Kunth) Barros, S. californicus subesp. Tatora (Kunth) T. Koyama, and Schoenoplectus tatora (Kunth) Palla, which are synonyms for Schoenoplectus californicus (14). However, the most abundant taxon in Lake Titicaca is Schoenoplectus Tatora (13, 20). The availability of this material in rural communities is extensive, as well as its traditional use.

The insulation capacity of totora and its suitability for use as an insulating material in the highlands of Puno, Peru, were analyzed. The tests were conducted in a laboratory at the University of Minnesota following the standard ASTMC1155-95:2013, which determines the thermal resistance of building envelope components based on in-situ data. The reported conductivity from these tests was 0.083 W/m·K (13), indicating its good thermal performance for insulation purposes. The fast growth rate, high renovation capacity, low density, spongy internal structure, and the favorable weight-resistance ratio make this material an intriguing option for studying its application in thermal insulation in the construction sector (21).

Another versatile material known for its properties, which can change repeatedly through a reversible hydration reaction and is totally and infinitely recyclable, is the dihydrate calcium sulfate (CaSO₄·2H₂O) commonly known as gypsum (22). The material has transitioned from artisanal to industrial, being one of the most common mineral binders with energy savings in its manufacturing process and low CO₂ emissions. It has a neutral pH and is usually white with desirable decorative properties. It is an excellent material for molding, fire resistance, and noise reduction. However, gypsum products have low water resistance (23). Several authors have studied the use of gypsum in combination with organic materials, such as incorporating wood waste into the gypsum matrix, for the development of false ceiling boards with improved thermal and acoustic properties (24). Gypsum boards are used in walls or ceilings with light gauge steel structure as the main fire-resistant material, in addition to thermal protection (25). Low thermal conductivity values for gypsum of 0.17 W/m·K have been recorded, indicating that it behaves as a good thermal insulator (26). For standard gypsum boards for ceilings according to the UNE-EN 12667 Standard, thermal conductivity values of 0.30 W/m·K have been shown. A Noise Reduction Coefficient (NRC) according to the EN ISO 10534-2 Standard of 0.12 (27) and density of 810 kg/m³ (28) have been registered. Its use in the study area would be appropriate due to its good thermal acoustic response properties and local availability in combination with totora.

The study was carried out in three stages. Firstly, the study location for the extraction of raw materials and the procedure for obtaining the panels according to the most commonly used weaving techniques by the local community were defined. For this purpose, the community of Chimu was chosen, located in the coastal area of Lake Titicaca at a latitude of 15° 51’ 18.3” South, a longitude of 69° 57’ 56.3” West, and an altitude of 3909 meters above sea level. The town is home to single-family rural dwellings and residents engaged in the extraction and weaving of totora blankets, as shown in Figure 1.

Three types of weaving techniques were chosen, called “Kesana”, “Hilada”, and “Hicalina”, for the evaluation of five types of panels named T1, T2, T3, T4, and T5, to which a layer of gypsum was added. Table 1 and Figure 2 show the details of the panels.

The following dimensions and thicknesses were considered to verify the behavior of each one in the testing process and to analyze which ones could self-support better. It was also determined which one responds better to the tests performed compared to the standard suspended modular ceiling panel that is placed on a support structure, the modules are supported without fixings and can be uninstalled freely (29). This arrangement is the most commonly used and the one that is desired to be replaced.

The assembled panels were taken to the laboratory to obtain their physical and durability properties. The moisture content of the totora panel was determined by calculating the ratio between its water content after natural drying and its weight in a dry state in an oven. Regarding water absorption, the guidelines suggested by ASTM C127-15 (30) for aggregates were considered, as there is no standardized procedure addressing water absorption by totora. Additionally, the apparent density was determined by weighing the dried totora-gypsum panel and dividing it by its apparent volume, which takes into account the pores or voids in the material. The durability against the fungus Rhizopus Stolonifer was tested following the ASTM D 2017-05 (31) and UNE-EN 350 (32) standards over a period of ten weeks. A piece was extracted from each panel every two weeks and observed under a microscope to verify the resulting damage. Three types of samples were used, referred to as M1, M2, and M3. Sample M1 consisted of totora without resin, M2 consisted of totora with a thin resin on one side, and M3 consisted of totora with resin on both sides. The resin used was varnish.

Next, the fire resistance properties were analyzed with reference to DIN 4102-1 (33) and ASTM E119-20 (34) for both exposed and non-exposed sides of the five types of combined panels, as well as impact resistance according to the Technical Report (35). Finally, the thermoacoustic properties were evaluated. For thermal insulation, thermal conductivity was assessed using the Thermal Conductivity Apparatus (36), which measured the amount of heat transferred by conduction through the material being studied, determining the time in which a mass of ice melted. To evaluate acoustic insulation, the NRC coefficient for materials was considered using a Soundproof Chamber (37).

This research presents the analysis of panels composed of totora and gypsum for use in ceiling applications in local rural housing, using different thicknesses to evaluate desirable properties. The tests conducted demonstrate that it is possible to produce a component that meets the established requirements according to current regulations. The suitability of using natural composite materials was found to be more convenient compared to conventional materials such as polystyrene or plastic foam. This implies a good alternative for the local community due to the easy availability of totora in the area, low cost, proximity to cultivation in Lake Titicaca, and high acceptance among the population.

Totora is a locally available material with beneficial properties that can contribute to the sustainability of rural housing. The totora panel alone has good insulation properties, but when combined with gypsum, it demonstrated even better performance. By forming a composite material that meets the requirements of lightness, durability, and strength, satisfactory results were achieved. With proper treatment and manufacturing, both materials can greatly improve the thermal and acoustic conditions of the common multipurpose spaces found in rural homes, and consequently the health of their occupants.

Considering that the greatest energy losses in rural dwellings in the mentioned areas occur through roof infiltrations, it is important to pay attention to this part of the building envelope and propose alternatives that can mitigate these losses. It should be taken into consideration that the implementations carried out must be accompanied by the care of the house’s carpentry and the management of the openings so that the panels can work properly. Panels are presented as a viable alternative to improve thermal and acoustic conditions with environmental and social benefits.