*5.3.2. Internal air quality*

Monitoring identified several spaces with very good IAQ. Given the prevalence of window opening this result was hardly surprising, but will of course have a thermal penalty. In cir‐ cumstances where window opening is common, the use of an MVHR system is not only in‐ effective but is also an additional primary energy burden on the dwelling as the fan continues to run at the same rate regardless of IAQ conditions. Where window opening was not prevalent, maximum values of CO2concentration were frequently found to rise and be sustained above recognised maximum desirable levels of 1000ppm. Figure 11 illustrates a particular situation from a bedroom in Dwelling 2 over the monitoring period but this is typical in monitored apartments throughout the project.

**Figure 12.** Physical parameters in Dwelling 2 twin bedroom – high CO2 concentrations

The bedrooms are of particular interest as windows are generally closed at night due to is‐ sues of external noise and as the occupants are asleep no further occupant intervention oc‐ curs. Accordingly these spaces are entirely reliant to the MVHR system to deliver ventilation and good IAQ.
