# Computational Modeling of the Thermal Behavior of a Greenhouse
## 2 Materials and Methods
### Computational Model  
The computer application EnergyPlus version 8.1 with graphical user interface DesignBuilder version 3.4.041 was used to simulate the dynamic thermal behavior of the  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Tests**} & **Ventilation** & **Airflow Rate** & **Auxiliary** & **Heating** \\  & **Type** & **(ac/h)** & **Heating** & **Set-Point (\({}^{\circ}\)C)** \\ \hline A1 & Natural & - & OFF & - \\ A2 & Forced & 12.9 & OFF & - \\ A3 & Forced & 14.7 & OFF & - \\ A4 & Natural & - & OFF & - \\ B5 & Natural & - & ON & 12 \\ B6 & Natural & - & ON & 20 \\ B7 & Forced & 12.9 & ON & 18 \\ C1 & Forced & 1.0 & OFF & - \\ C2 & Forced & 3.0 & OFF & - \\ C3 & Forced & 3.0 & OFF & - \\ \hline \hline \end{tabular}
\end{table}
Table 1: Experimental test parameters necessary for model validation [17; 18].  
Figure 3: Picture of one of the circular openings of the greenhouse with a ventilation duct attached.  
greenhouse model. This well-known computational tool was developed and applied mostly for more traditional structures, such as residential, office, and commercial buildings [19; 20; 21; 22; 23]. However, it has been used successfully in simulating considerably different structures from the aforementioned ones, such as data centers, outdoor telecommunications cabinets, or greenhouses [19; 24; 25].  
Figures 4 and 5 show the model of the greenhouse under study and its surrounding structures in order to include the shadow effects on the greenhouse during certain periods of the day.  
With the model's geometry defined, the following step was to set the building material's characteristics in the model. As such, the extensive library of material templates included with DesignBuilder was used for most of the greenhouse's materials. For the supporting wood structure, the template \"Woods-fr, pine\" was selected and modified to have a thickness of 0.03 m. This template was applied to the \"External walls\", \"Pitched roof (occupied)\", and \"Internal partitions\" sections of the model.  
The floor of the greenhouse is made from the natural terrain found in the greenhouse's location, and so the template \"Earth, common (0.5 m)\" was chosen. Air infiltration was considered in this model. Although no experimental data were available--as it is a small greenhouse built with special care for research purposes and located in a place relatively sheltered from the wind--an infiltration value of 0.2 ac/h (air chamber volume changes per hour) was considered. The properties of the surrounding buildings are also relevant, and so the \"Project component block material\" template was set for these structures. Table 2 summarizes the characteristics of the polyethylene cover, which were inputted manually, with the thermal conductivity being sourced from the ISO 10456 standard and the other necessary properties from [PERSON] et al. [18].  
Figure 4: Visualization of the greenhouse model (in gray) and surrounding structures (in purple).  
Figure 5: Close-up of the model of the greenhouse.  
A climatic data file containing the weather data of Covilha was used [26] for simulation purposes. This data file includes 2002 as the reference year. Furthermore, a \"10 time steps per hour\" setting was adopted, and the outdoor ambient air temperature was used as the criterion to determine which simulation day more closely matched the day of each experimental test. Additional details of the greenhouse modeling can be found in [27].