*4.3.3. Large diurnal range*

A diurnal CO2 range is normal and can be expected to be evident in the results due to the occupancy pattern of a bedroom, as described previously. It is however the size of the range produced, such as that seen prevalent in SP1 (Figure 3) is a concern. The bedrooms have ac‐ ceptable CO2 levels when empty but when they are occupied they fail to adapt. This obser‐ vation leads to an assumption that there is very little or no ventilation taking place during SP1. This conclusion is supported by unstable Ta and RH levels also presented in the CP. Reasons for poor ventilation could be attributed to the MVHR system not functioning as re‐ quired to produce the sufficient amount of air changes per hour needed for each room. There was no CP prior to SP2 to gain clarification from, however, a reduction in the diurnal range in SP2 shows that better ventilation must be taking place.

**Figure 7.** CP, House A & B, Bedroom 2

With this in mind, an obvious difference can be shown between the two study periods by comparing the best performing bedroom from SP2 with its counterpart in the first study. (Figure 5 and 6). SP2 shows much lower levels of CO2 than that recorded in the same bed‐ room in SP1. In fact SP1 results indicate unacceptable levels of CO2 within all the bedrooms of House A and B (Table 7). In SP2 only two of the eight bedrooms recorded levels above 1000ppm on a regular basis (>3 hours a day). Further to this, SP2's maximum levels are not

Although a crude representation, looking at the mean time per day that bedrooms spend above 1000ppm clearly strengths the visible difference shown in the graphs, between the

The most important inconsistencies are highlighted below and will be considered when dis‐

The temperature thermostats were possibly set too high in SP1. It is possible that the Ta re‐ corded for SP1 House A would have been considerably higher if the occupants had not opened the windows in the bedrooms so frequently. The need to naturally ventilate to dif‐ ferent degrees between House A and House B, but with similar temperature outcomes, sup‐ ports the observation of a difference in IAQ between the two houses. Likewise, it can be assumed that the thermostats in SP2 were set too low, resulting in one of the occupants al‐ tering the settings in House B to compensate. This evidence further identifies a difference between House A and House B. Whether the difference in Ta is due to construction type, a variation in MVHR system or a study limitation, the unacceptable Ta experience highlights the need for a greater degree of occupant control in order to achieve the ideal sleeping tem‐

RH levels remain constantly poor throughout both study periods and suggest that the MVHR

A diurnal CO2 range is normal and can be expected to be evident in the results due to the occupancy pattern of a bedroom, as described previously. It is however the size of the range

is producing air that is too dry, 30-40%. The reason for this unacceptable RH is unclear.

as high, and the minimum levels were also lower.

House A and B had different occupancy distributions

Thermostat increase occurred in House B during SP2

MVHR system was serviced in the interlude following SP1

Natural ventilation occurred during SP1

CO2 levels in both study period.

**4.3. Discussion**

cussing the results.

154 Sustainable Energy - Recent Studies

*4.3.1. Air temperature*

perature.

*4.3.2. Relative humidity*

*4.3.3. Large diurnal range*
