Ensayo en finca experimental La Higueruela-CSIC

It is acknowledged that there are limitations in this present study which may affect the results.

Lack of summer heat waves

The outdoor weather experienced during the recent summer seasons in Sydney, Adelaide and Brisbane were, on average, some of the warmest temperatures recorded during the calendar year. All cities often recorded daily maximum temperatures exceeding 40°C. That being said, they did not experience an official heat wave period, as defined by BoM. Therefore, the results presented here are about thermal comfort during moderate-to-hot summertime temperatures rather than during heat waves.

Indoor climate data

The amount of reliable data collected from the Brisbane households during the summer season was very low.

Adaptive comfort model applicability

The ASHRAE adaptive comfort model (de Dear & Brager 1998, 2002) and the associated adaptive comfort standard (ASHRAE 55-2010R) were based on large samples of office occupants (n = 22,000) from 160 buildings scattered across four continents. Whether or not that adaptive comfort concept can be generalised from office settings to a residential context was one of the key questions of this research.

This generalisation was strongly supported by the Sydney data in hand. Results from the study conducted in Adelaide indicated that the model was applicable for assessing thermal comfort in mixed-mode (naturally ventilated and air-conditioned) residential buildings.

3.10 Conclusions

This section presents the preliminary results from a thermal comfort study across residential houses in Sydney, Brisbane and in a housing development in Adelaide. So far, the Sydney study has recruited 30 participant households located throughout the Greater Sydney region. Compared to the population of Greater Sydney, participants in the sample had an average age of 30–39 and were highly educated with most having attended university and obtaining a degree at postgraduate or higher levels. The participants also had above-average income levels. Participants’ homes were a variety of stand-alone dwellings and apartments built from common construction materials, for example, concrete, timber and corrugated steel. The air conditioner units within these houses represented the more common air conditioner technologies found within residential buildings, for example, ducted and spilt systems.

The study in Adelaide included 20 householders involving 22 participants. While the number of samples was relatively small for a generalisation to be made for Greater Adelaide, there was a more even distribution of age groups, academic backgrounds and income levels of the participants in Adelaide than in Sydney. However, in terms of house locations, construction types and air conditioning systems used in houses, the majority of the samples in Adelaide were more homogenous as they nearly all came from the same housing development. The Brisbane sample, by comparison, comprised a range of family types ranging from a single adult to households of adults and children. Consistent with the demographics in the Sydney and Adelaide studies, the Brisbane participants also had above average income levels with 50% of households containing at least one adult working full-time.

78 A Framework for Adaptation of Australian Households to Heat Waves

The Brisbane houses did not require heating; however, split systems were the most common type of air conditioner throughout the sample population. These units were mainly located in the living room and bedroom, with the majority of houses having ceiling fans in their living areas and bedrooms.

In the Sydney study, between December 2012 and March 2013 (2012/13 summer season), the average indoor living room temperature during occupied hours (0700–

2100 hrs) was 25.0°C. Ranging between 20°C and 30°C, these temperatures were well within the boundaries of ASHRAE’s 80% acceptability limits (18°C to 28°C). These temperature ranges were fairly similar across other types of room, with the dining room apparently being slightly cooler, with an average indoor temperature of 23.6°C. These results are consistent with the finding that the majority (44%) of thermal sensation votes recorded within the participants’ houses were described as neutral. In the Adelaide study conducted between January and March 2012, from all the data from 20 houses, the average indoor temperature in the living room and bedroom without the air conditioner running was 24.5°C and 27.2°C respectively. Based on all the data recorded, the temperatures in the living room and bedroom were also mainly within the boundaries of ASHRAE’s 80% acceptability limits except for 7.2% and 12% of the time, respectively. The average indoor living room temperature recorded for the Brisbane sample was slightly warmer at 26.5°C, possibly due to the warmer outdoor conditions experienced during the study.

According to the data obtained from the comfort questionnaires, most participants adjusted what they wore according to the indoor temperatures. The participants in Sydney predominantly wore light clothing ensembles (59%): when binned according to concurrent indoor temperature, it was found that the percentage of participants who expressed their thermal sensation as slightly warm to warm increased. To accommodate for these warmer conditions, that is, indoor temperatures above 25°C, most participants were wearing light clothing ensembles. Furthermore, above this threshold, participants increased their usage of passive ventilation strategies, especially in the Sydney and Adelaide studies. Despite the availability of an air conditioner unit, the most preferred thermal adaptation employed by the participants was the opening of windows and/or doors (over 90%). In the Brisbane sample, however, the findings did not seem to fit this generalisation since the most commonly used ventilation strategy during the study was having the air conditioner on cooling mode (42.5%). These findings suggest that the participants were comfortable across a fairly broad range of temperatures. Between indoor temperatures of 18°C to 28°C, the range of average thermal sensations was within the region of slightly cool (-1) to slightly warm (+1).

Light clothing was also the most preferred ensemble option in the Brisbane and Adelaide samples, representing 72% and 63% of the total number of votes, which was reasonable considering that the study was conducted in summer. In terms of passive ventilation strategies, opening windows and doors as well as turning on fans were the two strategies that were most frequently employed. It was found that windows and/or doors were opened most of the time; however, employing this strategy to provide passive ventilation and cooling steadily decreased as the indoor temperatures increased. Conversely, the air conditioner was more frequently used as the temperatures increased, particularly in Brisbane.

In comparison with the adaptive comfort model, as presented in the ASHRAE Standard 55-2010 (ASHRAE 2010), the majority of neutral temperatures calculated for each participant in the Sydney study fell within the upper and lower limits of 80%

acceptability, confirming that the adaptive comfort model’s scope extends to residential settings. It appears that indoor temperatures between 20°C and 30°C could be deemed as an acceptable range of temperature for this sample of residential buildings.

A Framework for Adaptation of Australian Households to Heat Waves 79 In the Adelaide study, it appeared that indoor temperatures between 21°C and 30°C were acceptable during summer, These temperatures corresponded to times when the participants felt neutral and during which, for 43% of the time, windows and/or doors were opened, fans were turned on for 22% of the time, 18% of the time the air conditioner was turned on, while 17% of participants did nothing. Regression analysis of the data indicated that the participants started feeling slightly warm at indoor temperatures of about 27°C.

If a person is not employing any thermal adaptation at a given indoor temperature, then they can be assumed to be comfortable at that temperature. In the Sydney and Adelaide studies, 28°C was the maximum temperature at which ‘no ventilation’

strategies were in use and yet occupants still voted neutral. This temperature may suggest a new thermostat setting for cooling in the Adelaide climate (as opposed to 25.0°C as determined in the NatHERS); however, further studies will be required to validate this suggestion.

From the findings presented in this report, it is clear that existing adaptive comfort models, as described in ASHRAE Standard 55-2010 (2010), can be applied to residential homes, during hot weather, especially those in the context of Sydney.

80 A Framework for Adaptation of Australian Households to Heat Waves