ACTITUD

A number of temperature loggers were used throughout the living room of the Palmerston North house. The auto-correlations for these measurements look similar, as do the cross-correlations. The maximum cross-correlation between two temperatures will occur for a particular time lag between the two temperatures. Table 5.13 gives the time lag of the maximum cross-correlation for each pair of temperature loggers from the Palmerston North house. In Table 5.13 the logger at the top of the column leads the logger at the left of the row by the number of minutes shown (with a resolution of five minutes). In examining Table 5.13 loggers whose rows contain many large values are loggers whose temperatures lag behind the other loggers whereas loggers whose column contains many large values are loggers whose temperatures lead the other loggers.

Table 5.13 Time lag in minutes (resolution is 5 minutes) for each pair of temperature sensors within the room.

A non-zero entry indicates that the sensor at the top of the column leads the sensor at the left of the row by the number of minutes shown.

T2 T3 T5 T6 T7 T8 T9 T10 T11 T13 T14 T16 T17 T18 26954 TT 26976 TT 46101 TT T2 5 10 10 20 T3 5 5 5 20 T5 5 5 5 20 T6 5 5 5 15 T7 45 45 45 45 15 45 45 45 25 55 60 55 40 65 30 40 T8 30 30 30 30 30 30 30 5 35 40 40 25 50 15 25 T9 5 5 5 5 5 10 10 10 25 T10 5 5 5 20 T11 5 5 5 20 T13 25 25 25 25 20 25 25 30 35 30 15 45 10 15 T14 15 T16 10 T17 15 T18 5 5 5 5 5 10 10 10 25 TT26954 TT26976 10 10 10 10 10 10 10 20 20 20 5 30 5 TT46101 10 5 5 5 5 10 5 10 15 20 5 25

It can be seen that the sensors T7, T8 and T13 lag behind the other sensors whereas TT26954 seems to lead the other sensors. T7, T8 and T13 are all positioned along the southern internal wall of the living room with T7 and T8 being located within the wall unit. The Tinytag sensor TT26954 that leads all of the other sensors is located at the centre of the room upon the radiation shield of T14. This logger is perhaps more directly influenced by solar radiation than the other sensors and is less enclosed than the other sensors.

5.9 Closure

Eighteen temperature loggers were installed within the living room of a Palmerston North house with temperatures being recorded every five minutes. Included amongst these loggers was a vertical temperature array of four temperature loggers placed at heights of 0.4 m, 0.9 m, 1.4 m and

1.9 m. The sole space heating within the room was a flued gas heater whose output was monitored by placing a temperature sensor upon to tell when it is being operated. The hourly external temperature and global horizontal solar radiation were recorded by the automatic weather station at Palmerston North approximately 3 km away from the measured house.

From an exploratory analysis of the measured data, the height at which the temperature logger was placed appears to be an important determinant in the temperature reported by the logger.

To compare the vertical temperature distributions between houses, a house in Whitby had a vertical temperature array identical to the one used in Palmerston North installed and measurements were collected over two periods; one during summer and one during winter. During winter a woodburner was occasionally used to provide heating to the room.

The observed vertical temperature distributions were time dependent with the temperature level and curvature of the distribution being important dynamic parameters of the distributions. With the large amount of data collected, graphical analysis is useful. As three variables are of interest (temperature, time and height) graphing this data is not straightforward. A colour contour graph with the temperature as the suppressed z-value (the colour) was used and was seen to be effective in displaying the large amounts of data in a meaningful way.

Mathematical functions were fitted to the vertical temperature distributions. A low order function that fitted all three sets of data reasonably well was a modified quadratic function where the height of the maximum temperature (h) was fixed to a particular value for each of the sets of data used. The value for h for the different data sets varied and a better understanding of this variable would be useful. Fitting this modified quadratic function to the data allowed analysis of the temperature level and curvature of the vertical temperature distributions to be examined.

The curvature appears to be related to the heat input into the room. For the Palmerston North house the heat flows were large, vertical temperature gradients well defined and a clear relationship was seen between the use of the gas heater and curvature of the vertical temperature distribution. For the Whitby house the heat flows were smaller, the vertical temperature differences were smaller and the relationship between the calculated vertical temperature distribution curvature and the woodburner use was poor.

Temperatures from the same height from around the Palmerston North living room were also examined. Local temperature anomalies were observed and were possibly related to local heat flows due to nearby appliances or paths of low thermal resistance. As these anomalies are difficult

to correct for, the initial placement of loggers should be carefully considered to minimise the variations observed in the temperature measurements.

Cross correlations between the indoor temperature and the outdoor temperatures were examined for the Palmerston North (120 minutes) and the summer (105 minutes) and winter (300 minutes) Whitby data. The time lags of the cross correlations of the all of the temperature loggers used in the Palmerston North house were examined. Three loggers were seen to lag the other loggers while one logger was seen to lead the other loggers. The reasons for these time lags are not clear.