## 2 Methods
### Selection of IAQ Performance Indicators
#### 2.3.1 Airflows  
Each ventilation airflow is measured and corrected according to the calibration certificate at each of the ventilation components (air extraction in humid rooms, air supply in living room and bedrooms), and for both speeds, base speed (Q\({}_{\rm BASE}\)) and high speed  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **Slope** & **SSE** & **R\({}^{2}\)** & **RMSE** \\ \hline IAQ parameters (temperature, humidity) (ref. [PERSON]) & & & & \\ \hline T\(\rightarrow\)WOHLER (980) & 0.99 & 0.12 & 0.89 & 0.05 \\ \hline T\(\rightarrow\)NODE & 1.07 & 204 & 0.88 & 0.49 \\ \hline T\(\rightarrow\)NEMO & 0.99 & 386 & 0.79 & 0.62 \\ \hline RH\(\rightarrow\)WOHLER (980) & 1.00 & 1.81 & 1.00 & 0.19 \\ \hline RH\(\rightarrow\)NODE & 1.03 & 1300 & 0.62 & 1.25 \\ \hline RH\(\rightarrow\)NEMO & 1.07 & 2127 & 0.84 & 1.46 \\ \hline CO\({}_{2}\) (ref. [PERSON]) & & & & \\ \hline CO\({}_{2}\)\(\rightarrow\)WOHLER (980) & 0.98 & \(2.9\times 10^{3}\) & 1.00 & 7.8 \\ \hline CO\({}_{2}\)\(\rightarrow\)NODE & 1.03 & \(6.4\times 10^{5}\) & 0.97 & 28 \\ \hline CO\({}_{2}\)\(\rightarrow\)NEMO & 0.92 & \(9.9\times 10^{6}\) & 0.74 & 100 \\ \hline Number particle (Ref. Grimm) & & & & \\ \hline
0.3 \(\upmu\)\(\rightarrow\)GRIMM D & 1.03 & \(4.2\times 10^{8}\) & 0.92 & \(5.6\times 10^{2}\) \\ \hline
0.3 \(\upmu\)\(\rightarrow\)MET ONE 930/931 & 2.89/2.86 & \(1.9\times 10^{9}/6.2\times 10^{8}\) & 0.86/0.94 & \(1.4\times 10^{3}/1.4\times 10^{3}\) \\ \hline
0.5 \(\upmu\)\(\rightarrow\)GRIMM D & 0.94 & \(2.5\times 10^{7}\) & 0.86 & 137 \\ \hline
0.5 \(\upmu\)\(\rightarrow\)MET ONE 930/931 & 1.65/1.76 & \(2.6\times 10^{7}/6.7\times 10^{6}\) & 0.83/0.95 & 160/140 \\ \hline
1 \(\upmu\)\(\rightarrow\)GRIMM D & 1.02 & \(2.41\times 10^{5}\) & 0.83 & 13.4 \\ \hline
1 \(\upmu\)\(\rightarrow\)MET ONE 930/931 & 2.82/2.77 & \(1.8\times 10^{6}/6.3\times 10^{5}\) & 0.11/0.53 & 42/43 \\ \hline
2 \(\upmu\)\(\rightarrow\)GRIMM D & 0.89 & \(8.6\times 10^{4}\) & 0.88 & 8.04 \\ \hline
2 \(\upmu\)\(\rightarrow\)Met One 930/931 & 1.83/2.18 & \(4.2\times 10^{5}/1.9\times 10^{5}\) & 0.75/0.80 & 20/24 \\ \hline
5 \(\upmu\)\(\rightarrow\)GRIMM D & 0.95 & \(3.6\times 10^{3}\) & 0.90 & 1.7 \\ \hline
5 \(\upmu\)\(\rightarrow\)MET ONE 930/931 & 3.31/3.23 & \(1.3\times 10^{4}/7.5\times 10^{3}\) & 0.75/0.78 & 3.6/4.7 \\ \hline
10 \(\upmu\)\(\rightarrow\)GRIMM D & 0.98 & \(3.0\times 10^{3}\) & 0.84 & 1.5 \\ \hline
10 \(\upmu\)\(\rightarrow\)MET ONE 930/931 & 2.17/2.24 & \(4.1\times 10^{4}/7.0\times 10^{3}\) & 0.50/0.86 & 6.4/4.6 \\ \hline PM (Ref. Grimm) & & & & \\ \hline PM\({}_{2.5}\)\(\rightarrow\)GRIMM D & 0.97 & 481 & 0.69 & 0.60 \\ \hline PM\({}_{2.5}\)\(\rightarrow\)NODE C/NODE L & 0.97/0.82 & 941/746 & 0.39/0.38 & 0.84/0.75 \\ \hline PM\({}_{10}\)\(\rightarrow\)[PERSON] D & 0.64 & \(1.3\times 10^{5}\) & 0.28 & 9.84 \\ \hline PM\({}_{10}\)\(\rightarrow\)NODE C/NODE L & 0.10/0.08 & \(5.4\times 10^{3}/4.1\times 10^{3}\) & \(-1.95/-2.20\) & 1.99/1.75 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Correlation between the reference and low-cost devices.  
(\(\mathrm{Q_{HIGH}}\)). Starting from the airflows we calculate the ACRs (h\({}^{-1}\)) using Equation (1) and leaving out the part due to internal air leakage:  
\[\mathrm{ACR_{i}}=\frac{t_{BASE}*\mathrm{Q_{iBASE}}+t_{HIGH}*\mathrm{Q_{i,HIGH}}} {\mathrm{V_{i}}\left(t_{BASE}+t_{HIGH}\right)} \tag{1}\]  
where \(\mathrm{Q_{i}}\) (m\({}^{3}\cdot\)h\({}^{-1}\)) is the measured and corrected ventilation airflow in zone i, \(t_{BASE}\) (h) is the duration of the use of base speed ventilation, \(t_{HIGH}\) (h) is the duration of the use of high-speed ventilation and \(\mathrm{V_{i}}\) (m\({}^{3}\)) is the volume of zone i.