## 2 Construction Aspects for Energy Performance Improvement
### Greenhouse Construction
#### 2.2.1 Greenhouse Shapes and Their Impacts  
The shape of the greenhouse is the external geometric and structural configuration that directly influences energy efficiency, light harvesting and internal ventilation [67]. This shape is designed not only to withstand local weather conditions such as snow and strong winds but also to optimize sunlight capture [7; 65]. In summer, the goal is to minimize sun exposure to prevent overheating, while in winter, the goal is to maximize exposure to take advantage of natural warmth [68; 69]. In Figure 3, we observe the diversity of forms for agricultural greenhouses, each with unique characteristics. The Flat Roof Greenhouse is notable for its simple design, ideal for areas with less snow, but requires care with drainage and ventilation, see Figure 4d. The Quonset Greenhouses (Figure 4e), with their arched roof, are effective at dispersing winds and snow runoff, as well as maximizing sunlight capture, offering advantages such as wind resistance and modularity [7; 69]. Geodesic greenhouses or dome roofs (Figure 4c) stand out for their even distribution of sunlight and robustness against winds and snow, suitable for tall and energy-efficient plants, although they can be more expensive to build [70]. The Greenhouse in Serra or Chapel (Gable) (Figure 4b), combines functionality and aesthetics, optimizing sun exposure and providing space for taller plants, but with variable construction costs [71]. Modified arch greenhouses (Figure 4a), characterized by their elongated shape, are economical and versatile, perfect for seasonal crops and protection against weather extremes [69; 72]. Finally, the Sierra Roof Greenhouses offer excellent ventilation and maximize exposure to sunlight, making them ideal for large-scale agricultural productions, despite a higher initial investment [7; 28; 38; 69; 72]. Each type of greenhouse caters to different needs and preferences in terms of climate, cultivation, and budget. Greenhouses, if built in span shapes, are also classified as even-span, Uneven-span or multi-span [7; 69; 72; 73]. The even-span greenhouses have two equal sloping sides, forming a symmetrical roof (similar to the chapel-type greenhouse Figure 4b), and have a continuous and wide space, ideal for uniform productions and automation. Uneven-span greenhouses are similar to regular-span greenhouses, but with sloping sides of different heights and are more commonly used on sloping terrain or to adapt to specific sun exposure requirements. Multi-span greenhouses, on the other hand, are a set of greenhouses that have independent sections, allowing different micro-climates for various crops, as we can see in Figure 4f, Refs. [74; 75]. It is worth noting that the classification of greenhouses may vary depending on the source consulted and the geographic region. Table 3 presents a comprehensive overview of the advantages, disadvantages, and recommended climate of greenhouse forms, from the simple constructed flat greenhouses to the more complex saw-shaped roof greenhouses. The decision on the form of the greenhouse to be used depends on the cultivation objectives and local conditions, as well as the specific needs of each agricultural production. In addition, Table 4 provides a summary of the different forms of greenhouses and their respective indications. These tables provide information for farmers and designers who want to choose the most suitable greenhouse shape for their specific needs, considering the advantages, disadvantages, and indications of each greenhouse shape. There are many researchers who are dedicated to studying different forms of greenhouses and how they can be optimized to improve the use of solar energy and food production. It is a growing area of research, especially with the increased interest in sustainable solutions for food production and the use of renewable energy. Figure 4: Main Greenhouse Shapes.