# Demand Control Strategies of a PCM Enhanced Ventilation System for Residential Buildings
## 2 System Description  
A single floor low energy family house located in New York is studied and modeled in Energyplus. The housing project aims at reducing the embodied carbon footprint for building materials and reaching high indoor environmental quality and thermal comfort with low energy consumption, by applying PCM-enhanced ventilated window and demand control ventilation strategy. The house is built using sustainable straw panel walls and thermal bridging free foundations. The thermal properties of the constructions are given in Table 1. The details of the constructions can be found in [26]. The house uses a PCM energy storage for ventilation pre-cooling/heating for building energy conservation. Each bedroom is equipped with a PCM enhanced ventilation window (PCMVW). The living room is installed with one PCMVW and two PCM energy storage facades. The PCM facade adds extra thermal storage to the room, due to the high energy demand of the room. Figure 2 shows the position of the PCMVW and the PCM panels. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Construction** & **Material** & **Thickness (mm)** & **U value (W/m2K)** \\ \hline Wall & Pressed straw panel and wood fiberboard & 450 & 0.12 \\ Foundation & Wood fiber & 400 & 0.12 \\ Roof & Wood fiber & 600 & 0.045 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The thermal properties of the constructions. Figure 2: The room ID and PCM ventilation window (PCMVW) and PCM facade locations. The working principles of the PCMVW and PCM facade are described below:  
In summer, the PCM energy storage works as a cooling unit, to provide cooler air to the indoor environment during the day. The working principle of the PCMVW during summer is shown in Figure 3, which includes three ventilation modes:  
1. The PCM energy storage discharge mode (Figure 3a), which is in operation at night, where energy is discharged by the cold outdoor air, to remove the heat stored in the PCM during the previous operation mode. 2. The ventilation pre-cooling mode (Figure 3b), which is operated during the day, when the indoor air temperature is high, and ventilation pre-cooling is needed. The relatively hot ambient air is ventilated through the cool PCM energy storage before being supplied to the indoor room; meanwhile, by natural ventilation outdoor airflow through the VW, heat accumulated in the window cavity is removed. 3. The heat mode (Figure 3c), which is operated when the indoor room is overcooled. In this mode, outdoor air for ventilation is supplied through the VW, where it is heated up in the window cavity. The PCM energy storage facade works similar to that of the PCMVW. The working principle of the PCM facade is shown in Figure 4. It includes three ventilation modes:  
1. The PCM energy storage discharge mode (Figure 4a). At night, the relatively low-temperature ambient air is supplied through the PCM facade to discharge the heat in the PCM energy storage. Meanwhile, bypass night ventilation is also in operation, to cover the cooling demand of the room during the night. 2. Ventilation pre-cooling mode (Figure 4b). It operates when the indoor air temperature is too high, and ventilation pre-cooling is needed. The relatively high-temperature outdoor air is supplied through the cooler PCM energy storage plates, where it is cooled before being supplied to the room. 3. The bypass mode (Figure 4c). It operates when the indoor room is overcooled. The ventilation goes directly from the outdoors to the room. Figure 3: The working principle of the PCM ventilated window during summer [14]. (**a**) PCM discharge mode, when (hour \(<\) 7) or (hour \(>\) 20:00). (**b**) Ventilation pre-cooling mode, when \(\text{T}_{\text{indoor}}>\) 24 \({}^{\circ}\)C. (**c**) Heat mode, when \(\text{T}_{\text{indoor}}<\) 24 \({}^{\circ}\)C.  
Furthermore, the PCMVW provides pre-heated air to the indoor environment during winter. The PCM works as solar energy storage. The working principle of the PCMVW during winter includes three modes:  
1. The heat storage mode (Figure 5a).