2.2.1. Pre-Processing

The pre-processing of the BES model was carried out to prepare the input data using the following programs: Google SketchUp™ (3-D modeling program) software, and Transys3d (Add-on of TRNSYS program), Lawrence Berkeley National Laboratory (LBNL) Windows 7.7 software, Quick thermal conductivity meter (QTM-500). It is worth noting that the 3-D models for the multi-span greenhouse used in this study were prepared by using Google SketchUp™. Furthermore, Transys3d, an add-on of the TRNSYS program for Google SketchUp™, was used to prepare the IDF file of 3-D model. This was then imported as an input to TRNSYS-18. Figure 5 shows the 3-D model of the studied multi-span greenhouse with the Wide-span and the Venlo denoted as (a) and (b), respectively. The greenhouse coverings and screen materials are specific and cannot be used in conventional buildings; thermal screens are used inside the greenhouse during heating period to reduce heat loss to ambient weather to save heat energy and shading screens are used inside or outside of the greenhouse during the cooling period to minimize the solar heat gain inside the greenhouse which reduces greenhouse inside temperature and consequently reduces the cooling energy demand of the greenhouse, as well as different shading screens and strategies which effect the crop quality and yield [22]. To simulate the actual greenhouse indoor environment, greenhouse covers and thermal screens' physical, optical and thermal properties including thickness, thermal conductivity, solar, visible, and thermal, transmittance, emittance, and reflectance were used. For this specific purpose, the greenhouse covers' properties were taken from a study conducted by Valera et al. [23], with the summarized details presented in Table 2.

**Figure 4.** Flow diagram of the multi-span greenhouse Building Energy Simulation (BES) modeling.

**Figure 5.** 3-D model of the studied multi-span greenhouse (**a**) Wide-span (**b**) Venlo.


**Table 2.** Physical, optical, and thermal properties of the greenhouse coverings.

Furthermore, specific thermal and shading screens available in the South Korean market were used. It is worth noting that the properties of these materials are not in the literature, hence the need for characterization. The thermal conductivities of all the screens were measured by the QTM-500, a thermal conductivity measurement device; the details of the measuring process have earlier been published in Rasheed et al. [24]. Other properties of the screens, such as transmissivity, emissivity, and reflectivity for different types of radiation, were measured by the methodology described by Rafiq et al. [25]. A detailed summary of the physical, optical and thermal properties of the characterized screen are presented in Table 3. In addition, the greenhouse covers and screen material's properties were introduced into the LBNL Window 7.4 program to prepare a DOE-2 (readable by TRNBuild) file for each material. The DOE-2 is a specific file type which is used to introduce materials properties into the TRNSYS-18 for application on greenhouse 3-D models for further real-time simulation process.


**Table 3.** Physical, optical, and thermal properties of the screens.
