2.6.2. Improved Model: Definition and Test

Gumbarevic explained that the main goal of model improvement, is to minimize the heat transfer through the building envelope. For that reason, it is important to pay attention to the design and construction details in all delivery phases—from schematic and design phases up to the construction phase [36]. Because of the poor results obtained with the basic model simulations, the next step was the implementation of bioclimatic strategies for each climatic zone. For choosing the correct bio-climatic strategies, we used weather analysis software Climate Consultant V6 [24]. Using the ASHRAE 55 model for defining thermal comfort parameters, Climate Consultant software generated Givoni's diagrams for describing the most adjustable bio-climatic strategies for each climate (Figure 9); with the base construction systems, several changes were implemented to construct an improved model that should comply with the Mexican energy standard.(A graphic display of implemented strategies is showed on Figure 10)

For the V3 improved model, a continuous thermal insulation layer was proposed, using expanded polystyrene (EPS) with a thermal conductivity of 0.029 W/m2K, and a width of 6 cm. By using insulation, the thermal masses of the brick and concrete elements were enhanced. Several shading elements were added to the windows. For the improved V1 model, the implemented changes were: a continuous thermal insulation layer using expanded polystyrene (EPS) with a thermal conductivity of 0.029 W/m2K and a width of 3 cm; by using the insulation, the thermal mass of the brick and concrete elements retained heat gains for nocturne diffusion; horizontal shading elements on the south façade for sun heat control; shading elements for windows; and openings for sun heat control.

**Figure 9.** *Cont*.

**Figure 9.** Givoni's diagrams produced by Climate Consultant V6 software [24]. Each diagram describes the suggested bio-climatic strategies for reaching thermal comfort inside the improved models for each climatic zone.

For the improved W1 model, the construction system of the ceiling was changed from the previous joist and block concrete slab to a lightweight EPS-blocks concrete slab for thermal insulation. In addition, a continuous thermal insulation layer was proposed using EPS expanded polystyrene with a thermal conductivity of 0.029 W/m2K and a width of 3 cm. Using the insulation, the thermal masses of the brick and concrete elements were enhanced. The walls were modified, adding an extra layer of brick with a 3 cm air gap between them. For better ventilation flow inside the building, 30 cm was added to the interior height. The façade windows were modified, adding 30 cm tall operable ventilation openings for cross-ventilation. Shading elements were added to windows and openings. For the improved X1 model, the construction system and strategies were quite similar to the W1 model, including the EPS-blocks concrete slab, a thermal insulation layer, thermal mass, windows configuration, shading, and blinds. The difference between both models is the air gap between the two-brick layer. For X1, the air gap is 5 cm wide. The reason for the similarities between W1 and X1 is that they share climatic characteristics in terms of temperature and other variables. They have many isotherm areas (areas that have an annual temperature variation from 0 to 5 ◦C). The difference between them is the high relative humidity in the tropical X1 area.

For the improved Y1 model, the construction system of the ceiling was changed from joist and block concrete slab to a reticular lightweight EPS-blocks concrete slab for thermal insulation. A continuous thermal insulation layer was also proposed using EPS expanded polystyrene with a thermal conductivity of 0.029 W/m2K and a width of 6 cm. Using the insulation, the thermal masses of the brick and concrete elements were enhanced. The walls were modified, adding an extra layer of brick, with a 5 cm air gap between them. For better ventilation flow inside the building, 30 cm was added to the interior height. The façade windows were modified, adding 30 cm tall operable ventilation openings for cross-ventilation. Because of the high radiation in this location, the building receives unnecessary heat gains from the northern façade. To solve this problem, the improved model included shading elements for northern windows. Shading elements were added in windows and openings. Finally, for the improved Z2 model, the construction system of the ceiling was similar to the Y1 model. However, due to the extremely warm climate, a second ceiling was added, with a ventilated air gap of 15 cm. The second concrete ceiling

receives the direct radiation, and the cross-ventilation in the air gap dissipates the overheat. The ventilation method of this model relies on bulk airflow measures, driven by wind, to promote natural ventilation. Ventilation was enhanced also by promoting the stack effect by positioning ventilation openings near the roof (which is 20 cm higher than the other improved models.

**Figure 10.** Architectural details of the construction systems used in some of the improved models for testing. For more detailed information and the key for the numbered circles, see Appendix A.

This improved model included all the mentioned strategies, like 6 cm thermal EPS insulation, double brick layer with a 5 cm air gap, shading elements in windows, etc. The south façade windows were covered with a stationary during summer, and its leaves fall in winter (allowing direct solar heat gains). The interior height of the model was increased 60 cm, creating a 3.30 m height to allow the warm air to concentrate in the upper part of the interior space.

Using the SGSAVE complementary tools, certain special characteristics were introduced to all improved models:double-glass windows with a 4-cm air gap, and windows blinds for the south façade, with an operation calendar of 30% aperture in the summer. These improved models were constructed for testing the energy performance of the mostused construction system in Mexico (reinforced concrete elements with red brick walls and a foundation bed) in the different climatic zones in the country. To obtain a wider view of the desired results, we created improved models with different construction systems. For comparing the results with the traditional system, the two most-used traditional systems after reinforced concrete and fabric were chosen: the wood construction system and the adobe–metal sheets construction system. All the bio-climatic strategies that were used for the improved models were taken from a practical guide of 101 basic rules for low energy consumption [37].

The wood construction system (Figure 11) was composed of 1.8-cm wide Triplay OSB (Oriented Strand Bond) panels and timber structure in the walls and ceiling. The floor was a foundation bed of concrete, with 60 × 60 cm ceramic tile. The walls had a double Triplay OSB panel layer with a wood-cork thermal insulation 5-cm wide with a thermal conductivity of 0.04 W/m2K and a vinyl waterproof sheet for stopping condensations [38]. The adobe–metal sheet construction system (Figure 11) was composed of a reinforced concrete structure with walls with adobe blocks (mud and straw regional block). Because of the low bearing capacity of these walls, the model needs a lightweight structure for the ceiling. So, a wood-timber ceiling was proposed, with a floor composed of a foundation bed of concrete slab. The adobe–metal sheet construction is an experimental construction technique, inspired by bahareque vernacular system [39]. The bahareque system is composed of a bamboo frame structure, with a medium-height wall of adobe and a second wall of bamboo panels. The ceiling should be a lightweight structure, like straw or a light wood or bamboo latticework. For this option, the bamboo structure was replaced by a reinforced

concrete structure (for seismic resistance), and the walls were covered by a metallic sheet (corrugated galvanized steel), which has high heat reflectance.

The technical information of the traditional materials used in the proposed model construction elements was obtained from Appendix D of NOM-020-ENER-2011 [3]. For the remaining materials, the data were obtained from the digital catalogue of the Mexican construction store Home Depot [40].

**Figure 11.** Architectural details of the two construction systems used to compare the results with the traditional reinforced concrete and fabric walls system. For more detailed information and the key for the numbered circles, see Appendix A.
