## 2 Materials and Methods
### Description of the Studied Buildings
The setpoint temperature of supply air heating is 16 \({}^{\circ}\)C the whole year except June to August in which it is reduced to 14 \({}^{\circ}\)C. It is assumed that supply air temperature warms up by 1 \({}^{\circ}\)C due to fans and ducting. The air handling unit (AHU) is equipped with a district heated reheat coil, which is used for heating supply air. The SFP of the ventilation system is 1.8 kW/m\({}^{3}\)/s. The total air exchange rate of the building is 0.52 ACH in both old and new buildings. The room types and the airflow rates in different rooms are shown in Figure 3 in which positive values are the supply airflow rates and the negative ones the exhaust airflow rates. The air leakage rate of building envelope q\({}_{50}\) at 50 Pa pressure difference is 2 m\({}^{3}\)/hm\({}^{2}\). Table 2 shows the number of occupants in each apartment type. The average occupancy density is one occupant per 28 m\({}^{2}\). The activity level of 1.2 MET and adjustable clothing level (0.85 \(\pm\) 0.25 CLO) are used. It is assumed that there are no heat gains from occupants in the staircase and base floor. The presence of the occupants corresponds with the lifestyle of working families. Thus, the heat gains are spatial, and temporal based on their presence. Manually controlled blinds between the outer panes are used when someone is present in the room according to the occupancy profile and the intensity of solar radiation exceeds 100 W/m\({}^{2}\) on the windowpane. There are no blinds in the windows of the staircase. The heating system of both the old and new building is district heating (DH). The efficiency of the heat exchanger in the DH substation is 97%. Space heating is carried out by 70/40 \({}^{\circ}\)C water radiators and the heat distribution efficiency is 80%. The temperature setpoint of space heating is 21 \({}^{\circ}\)C in the apartments, except 22 \({}^{\circ}\)C in the bathrooms. On the staircase and basement floor, the setpoint of space heating is 17 \({}^{\circ}\)C. A mechanic cooling system is used in just some of the simulation cases that will be discussed in the following sections. The annual net heating demand of domestic hot water (DHW) is 35 kWh/m\({}^{2}\)[28] per heated net floor area of the building. It is assumed that DHW consumption is constant with time. Heat losses of the DHW circuit are 0.56 W/m\({}^{2}\) and 50% of the heat losses were assumed to end up with internal heat gains in the zones. The total annual electricity consumption of household equipment is 21.0 kWh/m\({}^{2}\)[28] per heated net floor area. The electric power of the appliances (W/m\({}^{2}\)) is assumed to be evenly distributed by the floor area of all the simulated zones in the apartments, and the appliances are used every day between 7:00-23:00. There are no appliances on the staircase or base floor. The total annual electricity consumption of indoor lighting is 7.9 kWh/m\({}^{2}\)[28], per total heated net floor area of the building. The electric lighting power (W/m\({}^{2}\)) is assumed to be evenly distributed by the floor area of all the simulated zones in the apartments and by the floor area of the staircase. There are no heat gains from lighting on the base floor. The usage time of the lights are:  
* May to August: between 21:00-23:00
* September to April: between 6:30-9:00 and 15:00-23:00 \begin{table}
\begin{tabular}{c c c} \hline \hline
**Apartment** & **Number of Rooms** & **Number of Occupants** \\ \hline A & 3 & 3 \\ B & 1 & 1 \\ C & 2 & 2 \\ D & 3 & 3 \\ E & 4 & 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The total number of occupants in each apartment type. The internal door of the bathrooms or WCs is always closed, but the other internal doors inside the apartments are always open. The air airtightness of the closed doors is taken into account in the simulation and the equivalent leakage areas at 4 Pa pressure difference are 0.02, 0.1, and 0.08 m\({}^{2}\) for the bathroom door, doors between the apartments, and the outdoor of the staircase, respectively.