In 2005, 6 out of 33 households operated a portable electric heater in the asthmatic child’s bedroom. Regrettably, data was lost on the bedroom temperature due to faulty temperature sensors in 3 out of the 6 households who operated a portable electric heater in the child’s bedroom, and in 2 out of the 27 households who operated for less than one hour a portable electric heater in the child’s bedroom. In 2006, 8 out of 36 households operated a portable electric heater and 1 out of 36 household operated a HP in the asthmatic child’s bedroom. Due to a faulty temperature sensor, 1 out of the 27 households, who operated a portable electric heater in the child’s bedroom for less than one hour, was missing.
Table 4.3 shows the percentage of time when the temperature was respectively below 12°C, below 16°C and between 18°C and 24°C, in the child’s bedroom, during occupied periods (8 pm - 7 am). It can be seen that, in 2005, the 3 heated bedrooms experienced a higher frequency of temperature in the 18°C to 24°C range (63% vs. 36%) and a lower frequency of temperature below 12°C (6% vs. 3%) than the 25 unheated bedrooms. However, despite these exposure differences, the average temperatures between the heated and unheated bedroom groups were not statistically different (17.2°C, 95%CI [15.2°C - 19.3°C] in the 3 heated bedrooms vs. 16.2°C, 95%CI [15.5°C - 16.9°C] in the 25 non-heated bedrooms, p-value = 0.48). Table 4.3 shows that, in 2006, the 9 heated bedrooms experienced a higher frequency of temperature in the 18°C to 24°C range
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than the 26 non heated bedrooms. Consistent with this result, the average temperature between both home groups were statistically different (17.3°C, 95%CI [15.3°C - 19.2°C] in the 9 heated bedrooms vs. 14.9°C, 95%CI [13.9°C - 15.8°C] in the 26 non heated bedroom, p-value = 0.05).
Table 4.3: Percentage of time when the bedroom temperature was below 12°C, below 16°C and in the recommended WHO range (18°C - 24°C) during the occupied period of 8 pm to 7 am.
Percentage of time, in winter/spring 2005, with a
bedroom temperature
Percentage of time, in winter 2006, with a bedroom temperature
N <12 °C <16 °C 18 °C -24 °C N <12 °C <16 °C 18°C - 24°C Portable electric heater
operated for more than
one hour per night 3 3 26 63 8 10 40 46
Heat pump operated for more than one hour
per night NA NA NA NA 1 0 0 100
No heater or heater use for less than 1 hour
per night 25 6 47 36 26 17 64 23
As the outdoor temperature was lower during the 2006 monitoring period than during the 2005 monitoring period, the percentage of time that the temperature in the child’s bedroom was below 12°C was higher in 2006 than in 2005 (10% vs. 3% for portable electric and 17% vs. 6% for non-heated bedrooms). This result is consistent with the low heat output estimate found in the bedrooms, during the 2006 monitoring, where only 4 out of 36 households had a heat output above 5 kWh per day for bedroom heating. Except the household operating the HP in the child bedroom, the heater usage was not sufficient, in the child’s bedrooms, to maintain the temperature within the healthy range.
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Figure 4.19: Percentage of time that children were exposed to the 18°C to 24°C recommended temperature range per night (8 pm - 7 am) in relation to the energy output from heaters located in
the child’s bedrooms in 2006.
Figure 4.19 shows the percentage of time that the children were exposed to temperatures between 18°C and 24°C in relation to the heat output during the occupied period (8 pm - 7 am). The bedrooms that achieved a temperature in the 18°C to 24°C range for 50% of the time or more are labelled from A to J. Bedroom A was the bedroom where a HP had been installed and used. This HP model was rated as having a power input of 1.08 kW and a coefficient of performance for heating of 3.70. Assuming that the HP was operated at two-thirds of the rated capacity, the heat output was estimated at 2.5 kW which gives an estimated heat output of 27.5 kWh per night. The child was exposed to a temperature above 18°C for the whole night. This is in contrast to the other bedroom with a HP installed but not used, where the child was exposed to temperature below 16°C for the whole night, with the temperature dropping below 12°C for two-thirds of the night.
Bedrooms B, C and D are bedrooms of households who operated a portable electric heater for 8.7 hours, 9.7 hours and 11.0 hours respectively during the night and thus, the children were exposed to temperatures above 18°C for 79%, 82% and 62% of the night respectively.
Bedroom E was a very small room (about 9 m2) and the temperature might be overestimated as the temperature sensor was very close to the heating source. This
B I G F J E D H A C 0 4 8 12 16 20 24 28 0% 20% 40% 60% 80% 100% Heat outp ut per nig ht (k W h) fr om heater s lo cated in th e child 's bedroom
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bedroom was located close to the living room where a HP had been operated extensively during the monitoring period. This child was exposed to temperatures above 18°C for 87% of the night.
Bedrooms F to J had no heater operated within the bedroom, but were receiving heat from heaters located nearby in the living rooms. These heaters are all high capacity heaters; either a replacement heater (a HP for F and H, a WPB for I and J or a WB for G). Installing a high capacity heater in the living room seems to have had a positive impact on the child’s bedroom temperature. In contrast, where a low capacity heater (UGH) was located in the living room, additional bedroom heater use was required in Bedroom B, to reach 18°C during 79% of the night.
Bedroom F was a particular case. One adult in the home was disabled, and for the well being of this person, the whole house was maintained above 21°C for 95% of the time. This was achieved by continuously operating the HP located in the living room.
Except for bedroom F, additional heating seems to be required in the child’s bedroom to achieve the 18°C recommended temperature for the whole night. Figure 4.19 shows that where there is a low level of heat transfer from the living room, such as when the living room has a low capacity heater, the minimum additional energy output needed to maintain 18°C in the bedroom for two-thirds of the night was estimated to be 18 kWh (Bedroom B), so 24 kWh will be needed to maintain 18°C for the whole night. Using the heater sizing tool from the ALF method (Stoecklein and Basset 2000) to size the required power input (kW) to maintain 18°C in a 16 m2 bedroom (with a 2004 NZBC insulation level, 25% of window area and one outside wall), we found that a minimum input of 2.1 kW was needed, which would give a 23.1 kWh heat output over the 8 pm - 7 am period. The result from the ALF heater sizing tool was consistent with the field measured values.
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