The occupants of the leisure center were surveyed in the reception area before and during the simulated demand response event. The questions asked were carefully chosen to ensure they were not leading the participants in any way. To remove any bias, the respondents were told that the purpose of the survey was to check their level of thermal comfort to ensure more enjoyable visits in future and did not specifically refer to any demand response event. The participants were asked to first comment on their comfort in terms of temperature, humidity, and air quality in the areas of the leisure center in which they had spent time (Fig. 6).
The most relevant question, regarding whether they noticed a change in conditions during their time in the building, was placed at the end of the survey. The reason for this was to ensure the respondents did not realize that this was the key question and to prevent them from answering differently because of its importance.
The respondents indicated their thermal satisfaction in the reception area (where the survey took place) and in any other area of the building where they had spent the previous 20 min. This is therefore counted as two votes per person, one for each area the user of the leisure center facilities had occupied. Satisfaction in the leisure center is only relevant to the experiment if it differs during the demand response event, compared to during normal operating conditions.
Figure 7 shows the proportion of survey respondents that noticed a change in conditions during their visit. The vast majority of the building users stated that they did not notice the change in conditions during the simulated demand response event (in gray). A “correct” change is a change that was noticed by the respondents during the event and is also supported by the measurements of the temperature, relative humidity, and CO2 levels in the leisure center at those times. A change that was noticed outside of this time, before (in the control group), or after is considered “incorrect,” as it was not caused by the simulated demand response event conditions.
The survey indicates that 76.5% of respondents did not perceive a change in thermal comfort, while 11.8% of interviewed occupants noticed the same change in conditions that is supported by the metered results. A further 11.8% of the respondents stated that they noticed a change in conditions that occurred outside of the test period; therefore, these changes do not relate to the demand response simulation.
The breakdown of the results is shown in Fig. 8. One correct response was that it became colder in the pool area, near the middle of the event; this is substantiated by the measured data. The air in the pool hall became 0.7 °C to 1.1 °C colder during the event. The exact time that this change occurred cannot be determined with hourly recordings. The faster a change occurs, the more likely an occupant is to notice the said change. The second correct response was that it became more humid in the reception area. This is also considered a correctly identified change, as this building occupant answered the survey at the end of the DR event, when measurements show that relative humidity in the reception area had indeed increased. Even though this answer came at the end of the DR event, the occupant had been present on site for the whole test; therefore, his answer is considered as being part of the DR event period.
Nine people answered the questions before the test, and eight people answered during the test. Since the people were interviewed while leaving the gym, the number of respondents was limited due to the short period of 2 h of the DR event. Due to the low numbers of participants, it is difficult to accurately or certainly say that there was no change in comfort levels. However, the results compiled show little to no dissatisfaction in the leisure center and indicate that this type of turn down demand response event could be implemented in leisure centers, with little to no impact on thermal comfort, given the right conditions. Further experiments would be needed to verify this result, ideally repeating the test on a very cold day in winter and a very warm day in summer, to check if these results have any weather dependency.
General satisfaction results
Figure 9 shows the overall satisfaction results in terms of air temperature, relative humidity, and air quality. Overall temperature satisfaction throughout the test was acceptable. There appears to be a significant change in how people perceive the thermal levels in the leisure center throughout the experiment. Before the test, the overall temperature satisfaction follows a bell curve, with 44% of respondents indicating that the temperature was “Just Right.” During the test, the majority of respondents (81%) was completely satisfied with the indoor temperature.
Humidity satisfaction varied; however, the overall majority of respondents (69%) indicated that the humidity was just right or only slightly too humid (“4” and “Just Right”). The responses did not differ in trends before and during the demand response event. Approximately the same number of people responded to each category in both time periods. However, the most extreme negative response occurred during the event. It is to be expected that the humidity in a pool area is greater than ideal indoor levels. Therefore, a lack of complete satisfaction with the humidity levels is acceptable.
Air quality satisfaction increased during the demand response event, compared to before. Before the test, the air quality in the leisure center was the same as normal operation, showing that the control group indicated a varied response to the air quality. The portion of the respondents that indicated the air quality was acceptable (“4” and “Just Right”) before the demand response event was just 44%, compared to the period during the simulation where that percentage went up to 88%.
Factors that influence the results
Some of the potential factors that could influence the perception of the thermal comfort of survey participants, while at the leisure center, were recorded during the survey. The type of exercise each respondent had performed immediately before the survey and the type of clothing they wore was documented. In general, those who had been engaged in walking, gentle exercise, or intense exercise show the highest portion of satisfactory response with the indoor air temperature and humidity levels. Swimmers generally had a poor perception of the air quality, as there were equal numbers of positive and negative responses. The number of layers of clothing worn by an occupant could affect their perception of the temperature and other indoor conditions. The analysis of the clothing items the occupants were wearing shows that they were dressed appropriately, considering the weather and type of exercise they were performing. Those performing intense exercise all wore a top with short sleeves and no jacket, while the majority of those performing less intense activities wore tops with long sleeves and sometimes had a light jacket on as well.
The weather in October of 2018 was highly erratic with the highest temperature of 19 °C, the lowest temperature of − 4 °C, and the humidity ranging from 43 to 100% in the month. However, the outdoor conditions did not vary greatly during the 2-h period of the test. The air temperature was 16 °C at 17:00 and 14 °C at 19:00, the outdoor RH changed from 77 to 88% from 17:00 to 19:00, and the sky was predominantly cloudy on the day of the test. The two degrees Celsius decrease in outdoor air temperature does not seem to have been felt by the occupants, even though the equipment was turned off for 2 h. This indicates that the building fabric was able to maintain comfortable indoor conditions during the demand response event.
From the previously mentioned studies on thermal comfort, it can be seen that gender may impact the participant’s response to the survey. More than half of the participants were male (61%). This could mean the results are not taking female sensitivity of temperature into account sufficiently for concrete results. In order to have unbiased results, in any future re-run of the trial, more effort should be made to ensure a balanced gender distribution from leisure center users.
The impact of age and body weight on the results was not considered in this study.