Statistical and quantitative association between the heating

The figures from previous section 4.3.2.1 illustrated the strong association between the heating profiles of the living room and those of the other rooms without analysing if the households that chose to heat e.g. their hall are the same as the households that chose to heat e.g. their bedrooms. However, this information is important e.g. for defining realistic sets of heating profiles on building level, for use e.g. in stochastic analyses. The associations are documented statistically in Table 4.4. That table shows if the odds of heating one room type is associated with the odds of heating another room type. The table does not include values related to the living room, kitchen or bathroom because those rooms were heated by nearly all households, resulting in a lack of statistical power when analysing their odds of being heated. Similarly, the table does not include associations with the garage, the basement or the attic because not enough households reported heating those rooms. Comparing all other rooms one with the other always resulted in very significant associations, but some were much stronger than others. Only one direct combination of two rooms had odds of being heated that were not significantly associated: the play room and the toilet. Based on the strongest associations with regard to their probability of being heated (Table 4.4) and also on the differences between their heating hours (Table 4.5) and set-point temperatures (Table 4.6), rooms can be clustered into groups. Because the discrete choice of heating a room or not is already analysed by means of odds ratios in Table 4.4, the quantitative figures on the heating hours shown in Table 4.5 and those on the set-point temperatures shown in Table 4.6 only relate to the rooms that are heated, thus corresponding to all dots in the figures of section 4.3.2.1, except the ones forming a horizontal line at zero heating hours. The percentages connecting two room types (row and column, upper right side) in Table 4.5 show, for the households that heat both types of room, the percentage of those households that heat them for a different number of hours per day. The values connecting two room types on the lower left side of the table show, for that percentage of the households that heat both types of rooms for a different number of hours, the average difference in heating hours associated with each room. For example, 35% of the households that heat both the living room and the master bedroom (41% of all households according to Table 4.1) do not heat these rooms for the same number of hours per day. On average, those 35% heat their master bedroom 6.7 hours less than the living room. Table 4.6 follows the same approach but with regard to the set-point temperatures.

The first cluster was already indisputably recognisable in the previous section and consists of the living area and the kitchen. Respectively 100% and 99%

reported heating those rooms. Of those 99%, only 2% report different heating hours and only 3% report different set-point temperatures (Table 4.5 and Table 4.6). For those rare cases, the kitchen is on average heated to 1.2°C higher temperatures but for 0.8 hours less each day.

A second, obvious room cluster consists of the children bedrooms and the master bedrooms. The odds of heating the children bedrooms if the master bedroom is heated are very high (OR=37.62, 95% CI[21.82, 76.71], p<.001) and less than 10% of the households that heat both types of bedrooms heat each type differently. They heat the master bedrooms on average 2 hours less and to 2°C lower temperatures.

A third, strongly correlated group consists of the hall, the toilet and the washing or storage room, with the hall being the most likely heated of all three (Table 4.1). Not only do they have very strong associations with regard to their odds of being heated (Table 4.4), if they are heated directly than their reported heating hours and set-point temperatures are rarely different (≤ 6% and ≤ 28%, respectively) and, when different, the difference is small (Table 4.5 and Table 4.6). By comparison, while their heating hours are also rarely different than those of the living room (≤ 10%), approximately 50% report heating those rooms to a lower temperature, on average by a difference of -3°C. This is also the reason why the office rooms are not included in this cluster: while their odds of being heated if the hall is heat are very high and while, in that case, the number of heating hours are rarely different (11%), their set point temperatures differ in 43% of those cases, showing values that are on average 2.5°C higher in the office rooms than in the halls.

The odds of heating the play room are much higher if the office room is also heated (Table 4.4), suggesting that these two room types could form a fourth strong cluster. They differ more with regard to their heating hours and set-point temperatures. If both are heated, 16% heat them for a different number of hours, heating the office rooms for on average 5.6 hours more (Table 4.5). 31% of those households also report a different set-point temperature, but some give higher values for the play room and others for the office room, resulting in no difference when taking the average (Table 4.6).

One room remains: the bathroom. 98% reported heating their bathroom, to on average less heating hours but higher temperatures than all other heated rooms. It is thus the room that is most likely being heated intermittently (see also Table 4.1).

Table 4.4: association (odds ratios OR) between the probabilities of heating different rooms: HPH

Table 4.5: difference between the heating hours of the heated rooms: percentage of cases with different self-reported values and average difference for those cases [h]: HPH

Δ heating hoursliv. r.kitchenplay r. office r.hallwash./s tor.r.toilet bathr. child. bedr. master bedr. living r. - 2%21%15%8%10%7%37%41%35% kitchen1.2- 20%15%7%10%6%37%41%35% play r. -9.9-10.2- 16%17%15%13%33%34%31% office r. -6.4-6.45.6- 11%10%12%33%38%31% hall-2.2-2.58.54.2- 6%3%32%33%30% wash./stor.r.-5.5-5.4-0.1-0.7-0.9- 2%27%34%30% toilet -1.9-1.513.55.80.33.0- 25%31%26% bathr. -7.9-8.1-0.3-5.4-8.8-7.2-9.4- 33%28% children bedr. -7.4-7.2-0.7-5.5-7.6-5.7-7.3-1.8- 6% master bedr. -6.7-6.71.1-4.9-7.2-5.4-7.6-1.5-2.1-

Table 4.6: difference between the heating set-point temperatures of the heated rooms:

percentage of cases with different self-reported values and average difference for those cases [°C]: HPH

Δ set-p. temperatureliv. r.kitchenplay r. office r.hallwash./s tor.r.toilet bathr. child. bedr. master bedr. living r. - 3%33%23%51%50%43%48%75%78% kitchen-0.8- 31%20%49%49%41%50%73%77% play r. -2.3-2.4- 31%44%48%36%54%50%51% office r. -2.0-1.90.0- 43%45%37%56%61%67% hall-3.1-3.2-1.2-2.5- 28%19%65%51%53% wash./stor.r.-2.9-2.9-2.0-2.20.2- 24%62%52%50% toilet -2.9-2.9-0.5-2.21.41.0- 62%55%56% bathr. 1.31.32.82.13.43.43.0- 73%77% children bedr. -2.8-2.9-2.1-2.4-1.1-0.8-2.1-3.7- 9% master bedr. -3.2-3.2-2.9-2.6-1.4-1.2-2.2-4.0-2.1-

4.3.3 Statistical analysis on the determinants of the