sustainability

Article The Significance of the Adaptive Thermal Comfort Limits on the Air-Conditioning Loads in a Temperate Climate

Aiman Albatayneh 1,* , Dariusz Alterman 2, Adrian Page 2 and Behdad Moghtaderi 2 1 School of Natural Resources Engineering and Management, German Jordanian University, P.O. Box 35247, Amman 11180, Jordan 2 Priority Research Centre for Frontier Energy Technologies and Utilization, The University of Newcastle, Callaghan, NSW 2308, Australia; [email protected] (D.A.); [email protected] (A.P.); [email protected] (B.M.) * Correspondence: [email protected]; Tel.: +962-06-4294444 (ext. 4218)



Received: 8 December 2018; Accepted: 7 January 2019; Published: 10 January 2019


Abstract: The building industry is regarded a major contributor to climate change as energy consumption from buildings accounts for 40% of the total energy. The types of thermal comfort models used to predict the heating and cooling loads are critical to save energy in operative buildings and reduce greenhouse gas emissions (GHG). In this research, the internal air temperatures were recorded for over one year under the free floating mode with no heating or cooling, then the number of hours required for heating or cooling were calculated based on fixed sets of operative temperatures (18 ◦C–24 ◦C) and the adaptive thermal comfort model to estimate the number of hours per year required for cooling and heating to sustain the occupants’ thermal comfort for four full-scale housing test modules at the campus of the University of Newcastle, Australia. The adaptive thermal comfort model significantly reduced the time necessary for mechanical cooling and heating by more than half when compared with the constant thermostat setting used by the air-conditioning systems installed on the site. It was found that the air-conditioning system with operational temperature setups using the adaptive thermal comfort model at 80% acceptability limits required almost half the operating energy when compared with fixed sets of operating temperatures. This can be achieved by applying a broader range of acceptable temperature limits and using techniques that require minimal energy to sustain the occupants’ thermal comfort.

Keywords: energy efficiency; adaptive thermal comfort; air-conditioning

1. Introduction The building industry is regarded a major contributor to climate change as energy consumption from buildings accounts for the release of around 33% of global greenhouse gas (GHG) emissions [1]. The effects of climate change can be lowered by low energy building design techniques that reduce greenhouse gas emissions. Many studies have shown that low consumption, energy-efficient buildings need passive design strategies and can improve indoor comfort while lowering energy consumption, allowing occupants to extend the period of non-mechanical heating or cooling [2,3]. Low energy buildings require a suitable thermal comfort model to accurately estimate the cooling and heating energy required to sustain the thermal comfort inside the building. The accuracy of the thermal comfort model is thought to be a favorable approach because it is cost-effective and reduces energy overconsumption [4]. The largest energy consumer in the European Union (EU) is the building sector, and toward the aim of more energy efficient buildings, a new revised Energy Performance of Buildings Directive in

Sustainability 2019, 11, 328; doi:10.3390/su11020328 www.mdpi.com/journal/sustainability Sustainability 2019, 11, 328 2 of 16

Europe (EPBD) (EU) 2018/844 working toward more energy efficient buildings has been published in the European Union Official Journal (L156) and will take effect on 9 July 2018 to hasten the pace of new energy-efficient buildings and the cost-effective renovation of current buildings’ in European Union (EU) countries. This requires EU countries to transfer the new elements of the EPBD into national law by March 2020 [5]. The application of passive design techniques requires knowledge of the climates to design an appropriate design for each climate. For instance, there are different climate zones in Australia that are similar to the major climates around the world. The cool temperate zone is mild to warm summers and cold winters, and in the higher parts of the Snowy Mountains, snow can fall at any time of the year. Space heating and cooling from different types of fuels consuming a significant amount of energy in Australia can be reduced by appropriate climate passive design such as higher thermal mass, especially to the internal walls facing north windows to absorb the heat during the winter day and reradiate it inside the building during the night; the facilitation of cross ventilation during cool summer nights; elimination of air drafts through leaky walls and windows; light colored roofs and darker walls, especially the northern walls, to absorb winter sun; shading the east and west walls in summer (i.e., trees); and bulk insulation and double glazed windows are needed. The precise thermal comfort design and operation of buildings and systems for heating, ventilation, and air conditioning (HVAC) must consider all of the factors involved. Building designers often overlook or incorrectly apply the standards. Design input values are often regarded as widespread values rather than suggested values to be used under precise environments. At the operational level, only a few variables are considered, with erratic impacts on the calculation of thermal comfort [6]. Thermal comfort is delineated by the psychological term “condition of mind”. The comfort level of the occupants in any environment can vary and adapt over time due to psychological factors. Individual perceptions of thermal comfort can be influenced by the recollection of past experiences. Thermal comfort is the human experience of the thermal environment, and it is based on the thermal sensation of the inhabitant [7]. Adaptation occurs when experiences in a certain environment moderate future expectations. This is an important element in understanding the variance between field results and predicted theoretical/design forecasts in free-run mode buildings [8]. Hard labor in hot humid environments is a real health and economic hazard for millions of workers and their families in tropical climates when they work beyond their thermal comfort levels [9]. Seven air-conditioned buildings in South Korea were used to assess the effects of the occupants’ control on their environment and their effects on cooling energy consumption. The findings suggest that the level of control of the occupants over their thermal environment could reduce thermal energy consumption by almost 10% without impacting occupant thermal comfort [10]. The thermal comfort of the inhabitant is factored by measuring the comfort zone of a certain value for the occupant [10]. The combinations of personal factors and indoor thermal environment that form the thermal conditions suitable to the majority of the occupants are categorized and called the thermal environmental conditions for human occupancy developed by the American Society of Heating, Refrigerating (ASHRAE) and HVAC Engineers. The ISO, CEN, and ASHRAE Standards deal with comfort matters in a similar way to providing standards (EN ISO 7730: 2005 and ASHRAE 55: 2017). These standards outline the classification of combinations of indoor thermal environments and their personal aspects, creating thermal environments suitable for the general population [11]. There are two main thermal comfort modules used by ISO, CEN, and ASHRAE:

• The predicted mean vote (PMV) and the predicted percentage dissatisfied (PPD) models. • Adaptive thermal comfort models.

EN15251 specifies the “indoor environmental input parameters for the design and assessment of the energy performance of buildings addressing indoor air quality, thermal environment, lighting, and acoustics” as a European standard that comprises standards for the four indoor environmental Sustainability 2019, 11, 328 3 of 16 factors of thermal comfort, air quality, lighting, and acoustics. This standard has been widely used in practice, and several scientific papers on issues related to the adequacy of the standard have been published [12–14]. The PMV is based on the principles of heat balance and data collected in a climate controlled environment under stable conditions. The PMV index predicts the public’s mean response, as per the ASHRAE thermal sensation scale (−1 = slightly cool, −2 = cool, −3 = cold, 0 = neutral, +1 = slightly warm, +2 = warm, +3 = hot). Note that ASHRAE (and CEN) provides a comfort zone consistent with 80% of satisfied people. This “could” be compared with a percentage of dissatisfied people equal to 20% (PMV from −0.85 to 0.85) [10]. Six variables distinguish PMV thermal comfort: air temperature, relative air velocity, mean radiant temperature, mean air humidity, clothing insulation, and metabolic rate. Many of these variables are obtained by means of sensors; but the assessment of metabolic rate and insulation of clothing depends on the individual standards: ISO 9920 (clothing), ISO 8996 (metabolic rate), and ISO 7726 (instruments and methods) [15–18]. The PMV model has strengths and limitations. For example, [19] determined the predicted mean vote (PMV/PPD) for metabolic rates and the insulation of clothing is difficult to accurately estimate. The PMV for thermal comfort also tries to find the response of environmentally friendly occupants in terms of heat transfer physiology and physics, which is a complex procedure. It does not take into account the psychological factors that play an important role in controlling thermal comfort conditions. Many field studies have found that PMV is difficult to use in the real world and can lead to inaccuracies in terms of predicting comfortable conditions as it depends on the respondents’ physiology and subjective perception [20]. A field study in an air-conditioned office building showed that the adaptive model improved the thermal acceptance of occupants when compared to the PMV/PPD model with lower energy consumption [21]. Surveys on many buildings have shown that acceptable indoor conditions are often not met, which suggests that the entire construction industry needs more precise methods for designing and studying indoor environments [22–24]. Many studies have focused on helping building and operators of building and HVAC systems meet different and complex standards for improving energy efficiency and indoor environmental quality [6]. The adaptive thermal comfort method was developed as a result of the above complications to help designers find the comfortable operative internal air temperature in free-run buildings. Note that the adaptive thermal comfort method only works in free-run buildings and not in air-conditioned buildings, whereas PMV/PPV only works well in air-conditioned buildings and not in free-running buildings [25]. This adaptive module has been developed by various empirical and experimental investigations; the internal air temperature can be calculated successfully by taking into account several factors such as the interaction of the inhabitants with their surroundings including when they change their clothes, opening/closing windows, the use of low-energy fans, drinking water, and drawing shades. One of the key results of adaptive theory is that people living in warmer climates can tolerate warmer temperatures indoors than those living in colder climates [26]. The comfort zone is around the neutrality/comfort line and represents the comfortable upper and lower temperature. The acceptability of 90% and 80% limits a comfort zone with an ideal comfort temperature of 2–3 ◦C on either side of the comfort line, which is considered an acceptable limit. If fans are available, a further 2 ◦C on both sides can be added to calculate the comfort zone value for very hot, dry, climate conditions. For humid climates, 1 ◦C can be added to determine the value of the comfort zone value on both sides [27]. The temperature range identified corresponds to 90% and 80% acceptability limits and could reach approximately 30 ◦C according to the ASHRAE 55-2017 Standard [28]. While the constant air-conditioning operational temperature (thermostat setting) in a temperate climate/Newcastle area in Australia was fixed during the whole year, the operational temperatures were between 18 ◦C and 24 ◦C. This narrow range of the thermostat setting causes the system to Sustainability 2019, 11, 328 4 of 16 be active most of the time because the building’s interior air temperature is outside the operational temperatures the majority of the time, which requires a significant amount of energy. Increasing the thermal comfort criteria by reducing the acceptability limits from 90% to 70% has a major impact on space-cooling energy consumption (saving more than 40%) in tropical regions and regions with a hot summer climate [29]. One benefit of an adaptive thermal comfort module is the inclusion of air velocity and humidity for operative temperature calculation requirements. However, research suggests that to analyze the impact of these two factors on the thermal comfort of the occupant, data from the occupants related to windows and doors opened or fans running were taken into account [30]. In 26 air-conditioned and 10 naturally ventilated classrooms, field experiments were conducted using surveys and physical measurements, and showed that humidity had a minimal impact on thermal comfort [31,32]. Naturally ventilated buildings consume less than half the energy of air-conditioned buildings as the inhabitants adapt to a much wider range of temperatures outside the comfort zone defined by the PMV model [10]. The PMV model also predicts that occupants will feel warmer than they are, thus encouraging the over-use of air conditioning [28]. The adaptive thermal comfort model (by ASHRAE Standard 55-2017 and EN 15251) is used for naturally ventilated buildings, while the PMV/PPD model can be applied in air-conditioned buildings as the thermal comfort between the two is inaccurately compared. Fanger recommended the expectation factor, “e”, to grasp the mean thermal sensation in a warm climate of the inhabitants of the actual non-air-conditioned building. The factor “e” varies between 1 and 0.5. It is 1 for air-conditioned buildings and for non-air-conditioned buildings, the expectancy factor depends on the duration of the warm weather annually, and whether these structures can be compared with air-conditioned buildings in the region; so it may be between 0.8 and 0.9 [33]. Mechanical temperature control can be lowered when people accept broader internal air temperatures, occasioning in lower energy usage and running costs; thus, it enhances the building’s economic and environmental performance [34,35]. Inhabitants with greater individual environmental control tend to accept a wider range of indoor temperatures. On average, they accept a lower operating temperature of 2.6 ◦C and showed a lower motivation to change their current environment when compared to those without personal control. Residents are recommended to interact with their thermal environment through openable windows and doors, low-energy fans, and to minimize the use of governable heating and cooling systems [36]. A case study in southern Spain involved a high-tech energy-efficient skyscraper which saved occupation hours, reducing the use of air-conditioning equipment by 28% and significantly reducing the energy consumption overall [37]. This research examined the effect of applying adaptive thermal comfort operative temperature on cooling and heating loads. The adaptive thermal comfort results were compared with the real data from the housing modules with installed air-conditioning systems with fixed sets of operation temperatures based on the predicted mean vote model.

2. Materials and Methods Observations from the full-scale housing test modules were used to provide the weather data and the internal air temperatures. These data were used to estimate the time where cooling and heating are essential to maintain thermal comfort for the occupants using two types of operational temperatures: the adaptive thermal model and the sets of real temperatures used on the site for the air-conditioning systems.

2.1. Adaptive Thermal Comfort and the Indoor Operative Air Temperature In this paper, four full-scale test modules (Insulated Cavity Brick (InsCB), Insulated Reverse Brick Veneer (InsRBV), Cavity Brick (CB), and Insulated Brick Veneer (InsBV)) were used to compare the time where cooling and heating is essential to obtain thermal comfort using the adaptive thermal comfort model and air-conditioning systems installed on the site. Sustainability 2019, 11, 328 5 of 16

The European thermal adaptive comfort standard BS EN 15251 is based on ASHRAE 55, and the comfort temperature is calculated in the same way (similar equations but with different coefficients). As there is currently no Australian standard, ASHRAE 55 was used. The adaptive thermal comfort temperatureSustainability for free-running 2019, 11, x FOR PEER buildings REVIEW (the comfort temperature Tc) can be calculated through5 thisof 16 equation [27]: As there is currently no Australian standard, ASHRAE 55 was used. The adaptive thermal comfort Tc = 17.8 + 0.31 × To (1) temperature for free-running buildings (the comfort temperature Tc) can be calculated through this where, equation [27]:

◦ Tc = 17.8 + 0.31 × To (1) To: Outdoor Running mean temperature ( C). ◦ Tc: Operativewhere, temperature ( C).

To: Outdoor Running mean temperature (°C). To find the adaptive thermal comfort 80% acceptability limits inside the building where at least Tc: Operative temperature (°C). 80% of the occupants are satisfied with these temperature ranges [27], we used Equation (2): To find the adaptive thermal comfort 80% acceptability limits inside the building where at least 80% of the occupants80% are satisfied acceptability with these limits temperature implies to ranges Tc ± 3.5 [27],◦C we used Equation (2): (2) 80% acceptability limits implies to Tc ± 3.5 °C (2) In the adaptive thermal approach, occupants are required to wear suitable clothing. Clothing insulation (Clo)In the used adaptive in these thermal calculations approach, was occupants between 0.5 are m required2·◦C/W forto wear the hot suitable days andclothing. 1.3 m Clothing2·◦C/W 2 for the coldinsulation days, however,(Clo) used these in these values calculations were not correctedwas between by the0.5 effectm ·°C/W of air for and the movement hot days and [38 ].1.3 m2·°C/W for the cold days, however, these values were not corrected by the effect of air and In this research, the adaptive thermal comfort model was used to establish new occupant thermal movement [38]. comfort limits to estimate the time (number of hours) where heating and cooling was required. In this research, the adaptive thermal comfort model was used to establish new occupant The reasonthermal for comfort using the limits adaptive to estimate thermal the comforttime (number model of overhours) other where thermal heating comfort and cooling modules was (i.e., therequired. predicted The mean reason vote for (PMV) using the and adaptive predicted thermal percentage comfort dissatisfied model over (PPD)) other thermal was because comfort it uses a widermodules range (i.e., of operativethe predicted temperature mean vote and (PMV) minimum and predicted energy techniques percentage to dissatisfied sustain the (PPD)) occupants’ was thermalbecause comfort it instead uses a wider of mechanical range of operative heating ortemper cooling.ature and minimum energy techniques to sustain the occupants’ thermal comfort instead of mechanical heating or cooling. 2.2. Full-Scale Test Modules 2.2. Full-Scale Test Modules At the University of Newcastle, Australia, an extensive research program has been proceeding for the past decadeAt the on University the thermal of Newcastle, performance Australia, of Australian an extensive housing. research This program has included has been building proceeding and observingfor thethe performancepast decade on of the four thermal housing performance modules of under Australian a range housing. of different This has weather included conditions. building Four modulesand observing were built the atperformance the University of four of Newcastle,housing modules Callaghan under Campus a range (longitude of different 151.7 weather and latitudeconditions.−32.91). The Four housing modules test were modules built at were the University chosen to of represent Newcastle, typical Callaghan forms Campus of construction (longitude in 151.7 and latitude −32.91). The housing test modules were chosen to represent typical forms of Australia [39–43]. construction in Australia [39–43]. All modules had a square floor plan of 6 m × 6 m as shown in Figure1 and were 7 m apart to All modules had a square floor plan of 6 m × 6 m as shown in Figure 1 and were 7 m apart to minimizeminimize wind blockage wind blockage and evade and evade shading. shading. A fan A fan coil coil unit unit for for heating heating or or cooling cooling was was installedinstalled in each of theeach modules of the modules to maintain to maintain a thermal a thermal comfort comfort level. level. For For cooling, cooling, chilled chilled water water was was pumped pumped into the modulesthe modules where thewhere temperature the temperature rise through rise through the heat the exchanger heat exchanger coil and coil the and water the water flow rateflow were rate measured.were For measured. heating, For the energyheating, consumed the energy byconsumed the heater by andthe theheater air and circulation the air circulation fan was measured fan was togethermeasured [40]. together [40].

(a)

Figure 1. Cont. Sustainability 2019, 11, 328 6 of 16

Sustainability 2019, 11, x FOR PEER REVIEW 6 of 16

(b)

(c)

(d)

(e)

Figure 1. Cont. Sustainability 2019, 11, 328 7 of 16

Sustainability 2019, 11, x FOR PEER REVIEW 7 of 16

(f)

(g)

FigureFigure 1. ( a1.) ( Fulla) Full scale scale test test modules; modules; (b) North North side side for for all all modules; modules; (c) South (c) South side for side all for modules; all modules; (d) Cavity Brick (CB) with walling layout; (e) Insulated Cavity Brick (InsCB) with walling layout; (f) (d) Cavity Brick (CB) with walling layout; (e) Insulated Cavity Brick (InsCB) with walling layout; Insulated Brick Veneer (InsBV) with walling layout; and (g) Insulated Reverse Brick Veneer (InsRBV) (f) Insulated Brick Veneer (InsBV) with walling layout; and (g) Insulated Reverse Brick Veneer (InsRBV) with walling layout. with walling layout. All modules shared these construction materials: clay tiles for the InsCB and CB modules, All modules shared these construction materials: clay tiles for the InsCB and CB modules, concrete tiles for the InsBV module, and coated corrugated sheets for the InsRBV with a 10 mm concrete tiles for the InsBV module, and coated corrugated sheets for the InsRBV with a 10 mm plasterboard ceiling with glass wool batts (R3.5 insulation) between rafters, and a 6.38 mm plasterboardlaminated ceiling clear glass with window glass wool in a batts light (R3.5colored insulation) aluminum between frame installed rafters, andin the a 6.38northern mm wall laminated of cleareach glass module window [44]. in aThere light coloredwas a heavily aluminum insulated frame door installed in the in southern the northern wall wallto eliminate of each moduleany heat [ 44]. Therelosses was and a heavily provide insulated access to door the building in the southern [45]. wall to eliminate any heat losses and provide access to the buildingThe main [45 difference]. between the modules was the walling systems, so each module was named basedThe main on their difference walling betweensystem. Note: the modules the R-value was is the the walling thermal systems,resistance so for each each module walling was system, named basedalso on called their R walling (K·m2/W) system. [46]. Note: the R-value is the thermal resistance for each walling system, also calledA Rtotal (K ·ofm 1052/W) sensors [46]. were fitted in each module to record the internal and external conditions everyA total 5 ofmin 105 for sensors 24 h/day were over fitted the in testing each module period tousing record Datataker the internal DT600 and data external loggers conditions (Data everyElectronics 5 min for (Aust.) 24 h/day Pty over Ltd the7 Seismic testing Court period Rowville, using Datataker VIC, 3178 DT600 Australia). data loggersThe external (Data weather Electronics conditions (air temperature, wind speed and direction, relative humidity, ground temperature, (Aust.) Pty Ltd 7 Seismic Court Rowville, VIC, 3178 Australia). The external weather conditions incident solar radiation on each wall surface and roof) were recorded for each module [39]. The (air temperature, wind speed and direction, relative humidity, ground temperature, incident solar internal environment conditions (temperature and heat flux profiles through the walls, slab and radiationceiling, on internal each wall air temperature surface and and roof) relative were recorded humidity) for were each also module recorded. [39 ].The The internal internal temperature environment conditionswas measured (temperature at a 1200 and mm heatheight flux inside profiles the building through with the no walls,ventilation slab inside and ceiling,the modules internal [45]. air temperatureThe sensors and were relative installed humidity) in each module were alsowith recorded.a minimum The of 40 internal sensors as temperature required by ASHRAE was measured 55 at a 1200to measure mm height the thermal inside comfort the building performance with no of ventilation a small room. inside The the sensors modules were [45 distributed]. The sensors on the were installedwalls inand each in the module middle with of the a module minimum away of from 40 sensors the occupied as required boundary, by ASHRAE radiation, 55and to diffusers. measure the thermal comfortThe data performancewere recorded of using a small Datataker room. DT600 The sensors data loggers were distributedevery 5 min for on the24 h/day walls over and the in the middletesting of the period. module In this away research, from the mean occupied radiant boundary, temperature radiation, was calculated and diffusers. by finding the average temperatureThe data were of all recorded sensors located using Datataker inside the room DT600 and data the loggers operativ everye temperature 5 min for was 24 calculated h/day over by the testingfinding period. the average In this research, air temperature the mean for the radiant sensors temperature located in the was middle calculated of the bybuilding finding at thedifferent average heights of 0.5 m, 1 m, and 1.5 m. The accuracy of the PMV values was adequate only when the temperature of all sensors located inside the room and the operative temperature was calculated by difference between the mean radiant temperature and the air temperature was less than 5 °C [47]. finding the average air temperature for the sensors located in the middle of the building at different heights of 0.5 m, 1 m, and 1.5 m. The accuracy of the PMV values was adequate only when the difference between the mean radiant temperature and the air temperature was less than 5 ◦C[47]. Sustainability 2019, 11, 328 8 of 16 Sustainability 2019, 11, x FOR PEER REVIEW 8 of 16 Sustainability 2019, 11, x FOR PEER REVIEW 8 of 16 SeveralSeveral experiments experiments were were made made to to examine examine the the thermal thermal performance performance of of the the housing housing modules modules usingusing air-conditioningSeveral air-conditioning experiments systems systems were by bymade maintaining maintaining to examine the the the internal internal thermal air air performance temperature temperature of of ofthe each each housing module module modules within within fixedfixedusing temperature temperature air-conditioning ranges ranges systems (between (between by maintaining18 18 °C◦C and and 24 24the °C).◦ internalC). Heating Heating air temperaturewas was turned turned ofon on each when when module the the module’s module’s within internalinternalfixed temperature air air temperature temperature ranges dropped dropped (between below below 18 °C 18 18 and °C◦C and24 and °C). the the Heating heating heating wassystem system turned continued continued on when until until the 20module’s 20 °C◦C was was internal air temperature dropped below 18 °C and the heating system continued until 20 °C was reached,reached, with with the the cooling cooling being being activated activated at at 24 24 °C◦C and and continuing continuing until until 22 22 °C◦C was was reached reached [46]. [46]. reached, with the cooling being activated at 24 °C and continuing until 22 °C was reached [46]. 3.3. Results Results and and Discussion Discussion 3. Results and Discussion TheThe average average internal internal and and external external air air temperatures temperatures recorded recorded over over one one year year were were used used for for the the The average internal and external air temperatures recorded over one year were used for the validationvalidation and and are are presented presented in in Figure Figure 22;; thethe blackblack lineslines indicateindicate thethe air-conditioningair-conditioning operationoperation validation and are presented in Figure 2; the black lines indicate the air-conditioning operation temperatures.temperatures. TheThe narrownarrow temperatures temperatures for thefor thermostat the thermostat setting causedsetting the caused internal the air temperaturesinternal air temperatures. The narrow temperatures for the thermostat setting caused the internal air temperaturesto fall outside to the fall operation outside temperaturesthe operation of temperat the air-conditioningures of the air-conditioning system most of the system time andmost required of the temperatures to fall outside the operation temperatures of the air-conditioning system most of the timecooling and or required heating. cooling The thermostat or heating. settings The thermo were constantstat settings for winter were consta and summernt for winter and did and not summer interact time and required cooling or heating. The thermostat settings were constant for winter and summer andwith did the not external interact environment. with the external The air-conditioning environment. The systems air-conditioning inside the modules systems in inside the Newcastle the modules area and did not interact with the external◦ environment.◦ The air-conditioning systems inside the modules inhad the temperature Newcastle area settings had betweentemperature 18 Csettings to 24 C.between 18 °C to 24 °C. in the Newcastle area had temperature settings between 18 °C to 24 °C.

FigureFigureFigure 2. 2. 2.InternalInternal Internal air air air temperatures temperatures temperatures and andand temperature temperaturetemperature rangrang rangeseses betweenbetween between 18 18 °C◦C and and 2424 24 °C°C◦C whenwhen when using using using the the the air-conditioningair-conditioningair-conditioning systems systems systems for forfor the thethe CB CBCB module. module.module.

TheTheThe number number number of ofof hours hourshours outside outsideoutside the thethe thermal thermalthermal comforcomfor comforttt zonezone zone forfor for the the Cavity Cavity BrickBrick Brick (CB),(CB), (CB), InsulatedInsulated Insulated ReverseReverseReverse Brick Brick Brick Veneer Veneer Veneer (InsRBV), (InsRBV),(InsRBV), Insulated InsulatedInsulated Brick Brick Veneer Veneer (InsBV),(InsBV), (InsBV), and and Insulated Insulated CavityCavity Cavity BrickBrick Brick (InsCB), (InsCB), (InsCB), modulesmodulesmodules were were were 5139, 5139,5139, 4498, 4498,4498, 4476, 4476,4476, and andand 3805, 3805, respective respectively,respectively,ly, forfor for thesethese these temperature temperature settings,settings, settings, asas as shownshown shown in in in FigureFigureFigure 3.3 . 3.For For For more more more than than half half of of the the year, year, aa mechanicalmechanical systemsystem was required with with almost almost twotwo times times ◦ moremoremore time time time needed needed needed for forfor cooling coolingcooling th thanthanan heating heatingheating due due to to thethe lowlow temperaturetemperature settings settings ofof of maximummaximum maximum 24 24 24 °C °C C (the(the(the cooling cooling cooling mode mode mode was was was activated). activated). activated).

FigureFigure 3. 3.Number Number ofof hourshours perper yearyear required for heat heatinging and and cooling cooling and and the the total total for for heating heating and and Figurecoolingcooling 3. using Numberusing air-conditioning air-conditioning of hours per to year maintainto maintainrequired temperatures tempfor heateraturesing between and between cooling 18 ◦ C18 and °C 24theand◦ Ctotal 24 inside °Cfor eachinsideheating module. each and coolingmodule. using air-conditioning to maintain temperatures between 18 °C and 24 °C inside each module. Sustainability 2019, 11, 328 9 of 16 Sustainability 2019, 11, x FOR PEER REVIEW 9 of 16

◦ ◦ TheThe fixed fixed set set of of temperatures temperatures for for air-conditioning air-conditioning systems systems within within 18 18 °CC and and 24 24 °CC maintained maintained thermalthermal comfort. comfort. Interestingly, Interestingly, the the cooling cooling mode mode was was also also activated activated when when the the temperature temperature exceeded exceeded ◦ 2424 °CC even inin the the winter winter season season because because the modules the modules experienced experienced the warmer the internalwarmer air internal temperature air temperaturedue to solar due ingress to solar andthis ingress desired and energy this desired was removed. energy Thewas temperature removed. The then temperature dropped down then to ◦ dropped22 C and down the systemto 22 °C consumed and the system extra energyconsumed for coolingextra energy in winter. for cooling in winter. ThisThis indicates indicates that that the the fixed fixed thermostat thermostat settings settings affect affect the the overall overall energy energy consumptions consumptions of of the the modulesmodules and and in in some some scenarios scenarios may may provide provide false false estimations estimations of of the the thermal thermal performance performance of of the the modules.modules. This This may may work work against against some some modules modules (e.g., (e.g., the the InsBV InsBV module) module) since since the the warmer warmer module module at at dayday time time in in winter winter activated activated the the air-conditioning unitunit toto coolcool it it down, down, and and again, again, the the unit unit activated activated the theheating heating mode mode overnight overnight to to compensate compensate for for the the lost lost energy. energy. ◦ ◦ InIn more more detail, detail, the the fixed fixed set set of of temperatures temperatures for for air-conditioning air-conditioning systems systems within within 18 18 °CC and and 24 24 °CC maintainedmaintained thermal comfort.comfort. Interestingly, Interestingly, the th coolinge cooling mode mode was also was activated also activated when the temperaturewhen the ◦ temperatureexceeded 24 exceededC even 24 in the°C even winter in seasonthe winter because season the because modules the experienced modules experienced a warmer internala warmer air internaltemperature air temperature due to solar due ingress to solar and ingress this desired and this energy desired was energy removed. was The removed. temperature The temperature then dropped ◦ thendown dropped to 22 Cdown and theto 22 system °C and consumed the system extra consumed energy forextra cooling energy in for winter. cooling in winter. ForFor example, example, thethe following following results results were were for thefor winter the winter period period from early from August early (southern August hemisphere).(southern hemisphere).The internal The air temperatureinternal air temperature of the modules of the for modules a three day for perioda three underday period controlled under conditions controlled is conditionsshown in Figureis shown4 for in different Figure test 4 for modules, different together test modules, with the correspondingtogether with variations the corresponding in external variationstemperature. in external There were temperature. less heating/cooling There were interventions less heating/cooling for the CB andinterventions InsCB modules for the as aCB result and of InsCBthe internal modules thermal as a mass result dampening of the internal the internal thermal temperature mass dampening fluctuations, the but internal overall, thetemperature energy use fluctuations,was of a significantly but overall, higher the magnitudeenergy use for was InsBV of a and significantly InsRBV. This higher indicates magnitude that the fixedfor InsBV thermostat and InsRBV.settings This affected indicates the overall that the energy fixed thermostat consumptions settings of the affected modules the andoverall in someenergy scenarios consumptions may have of theprovided modules false and estimations in some scenarios of the thermal may have performance provided false of the estimations modules. Thisof the may thermal work performance against some ofmodules the modules. (e.g., theThis InsBV may work module) against since some the modules warmer module(e.g., the at InsBV day timemodule) in winter since activatedthe warmer the moduleair-conditioning at day time unit in winter to cool activated it down, the and air-conditioning again, the unit activatedunit to cool the it heatingdown, and mode again, overnight the unit to activatedcompensate the heating for the lostmode energy overnight as shown to compensate in Figure4. for the lost energy as shown in Figure 4.

FigureFigure 4. 4.InternalInternal air air temperatures temperatures of of all all modules modules under under controlled controlled air air conditions conditions [46]. [46 ].

TheThe average average internal internal and and external external air air temperatures temperatures were were used used again again to to estimate estimate the the occupants’ occupants’ adaptiveadaptive thermal thermal comfort comfort range. range. The The adaptive adaptive therma thermall comfort comfort settings settings occurred occurred to to be be more more flexible flexible duedue to to a awider wider range range of of internal internal air air temperature temperature limits. limits. The external and internal temperatures and the adaptive thermal comfort ranges of the 80% acceptability limit were calculated for all modules. The black lines show the higher and lower 80% Sustainability 2019, 11, 328 10 of 16

Sustainability 2019, 11, x FOR PEER REVIEW 10 of 16 The external and internal temperatures and the adaptive thermal comfort ranges of the 80% Sustainability 2019, 11, x FOR PEER REVIEW 10 of 16 acceptabilityacceptability limits limit werefor the calculated CB module for allas seen modules. in Figure The black5. The lines thermal show comfort the higher temperature and lower zones 80% wereacceptabilityacceptability expanded limitslimits to 22.7 forfor thethe°C CBandCB module module29.7 °C asasin seen seensummer inin FigureFigure and 5 19.6.5. The The °C thermal thermalto 26.6 comfort °Ccomfort in winter. temperature temperature These zoneswider zones ◦ ◦ ◦ ◦ rangeswerewere expandedexpanded saved massive to to 22.7 22.7 amountsC °C and and 29.7 of 29.7 operationalC °C in summerin summer energy. and and 19.6The 19.6indoorC to °C 26.6 airto temperatureC26.6 in winter.°C in winter. Thesefor all widerhousingThese rangeswider test modulessavedranges massive saved fell outside massive amounts the amounts of thermal operational of comfort operational energy. ranges Theenergy. only indoor inThe June air indoor temperature and airJuly, temperature remaining for all housing forwithin all test housing that modules range test forfellmodules the outside rest fell of the outsidethe thermal year. the comfort thermal ranges comfort only ranges in June only and in July, June remaining and July, withinremaining that within range for that the range rest offor the the year. rest of the year.

Figure 5. Internal air temperatures and thermal comfort ranges (80% acceptability higher/lower) Figure 5. Internal air temperatures and thermal comfort ranges (80% acceptability higher/lower) limits Figure 5. Internal air temperatures and thermal comfort ranges (80% acceptability higher/lower) limitsfor the for CB the module CB module for one for year. one year. limits for the CB module for one year. TheThe totaltotal numbernumber of of hours hours per per year year with with the internalthe internal temperatures temperatures outside outside the occupants’ the occupants’ thermal thermalcomfortThe zonecomfort total for number zone the modules for of thehours ismodules shown per year inis Figureshown with 6the .in Mechanical Figureinternal 6. temperatures Mechanical heating or cooling heatingoutside was or the requiredcooling occupants’ was for required2623,thermal 2499, forcomfort 2119, 2623, and zone2499, 1921 for2119, h perthe and yearmodules 1921 for theh isper Cavity shown year Brickfo inr theFigure (CB), Cavity Insulated 6. MechanicalBrick Reverse(CB), Insulatedheating Brick Veneer or Reverse cooling (InsRBV), Brick was VeneerInsulatedrequired (InsRBV), for Brick 2623, Veneer Insulated 2499, (InsBV), 2119, Brick and and Veneer 1921 Insulated h (InsBV),per year Cavity andfor Brick the Insulated Cavity (InsCB), CavityBrick respectively. (CB), Brick Insulated (InsCB), Just a quarterReverserespectively. of Brick the JustyearVeneer a was quarter (InsRBV), required of the forInsulated year heating was Brick required and coolingVeneer for heating using(InsBV), the and and adaptive cooling Insulated approach. using Cavity the adaptive Brick (InsCB), approach. respectively. Just a quarter of the year was required for heating and cooling using the adaptive approach.

FigureFigure 6.6. NumberNumber ofof hours hours for for heating, heating, cooling, cooling, and and the totalthe total time (heatingtime (heating + cooling) + cooling) for each for module each moduleusingFigure the using6. 80%Number the acceptability 80% of acceptabilityhours limits for forheating, limits the adaptive for cooling, the adaptive thermal and th thermal comforte total timecomfort approach. (heating approach. + cooling) for each module using the 80% acceptability limits for the adaptive thermal comfort approach. It was again confirmed that all of the modules performed poorly from April until September so It was again confirmed that all of the modules performed poorly from April until September so heating was required, and this trend was noticed for both approaches (adaptive thermal and with the heatingIt waswas again required, confirmed and this that trend all of was the noticedmodules for performed both approaches poorly from (adaptive April untilthermal September and with so fixed air-conditioning thermostat settings). theheating fixed wasair-conditioning required, and thermostat this trend settings). was noticed for both approaches (adaptive thermal and with Significant savings in cooling energy usage were observed in the summer months when compared the fixedSignificant air-conditioning savings in thermostat cooling energy settings). usage were observed in the summer months when with the air-conditioning fixed thermostat setting due to the wider range of temperatures for the comparedSignificant with the savings air-conditioning in cooling fixed energy thermostat usage weresetting observed due to the in widerthe summer range of monthstemperatures when forcompared the adaptive with thethermal air-conditioning model (22.7 fixed °C–29.7 thermostat °C). The setting percentage due to of the time wider for coolingrange of dropped temperatures by a staggeringfor the adaptive ratio ofthermal 97%, 92%,model 96%, (22.7 and °C–29.7 92% for°C). the The CB, percentage InsBV, InsRBV, of time andfor cooling InsCB, droppedrespectively. by a Thesestaggering could ratio be easilyof 97%, achieved 92%, 96%, by andsmall 92% extra for theactions CB, InsBV,taken byInsRBV, the occupants and InsCB, to respectively.restore the These could be easily achieved by small extra actions taken by the occupants to restore the Sustainability 2019, 11, 328 11 of 16

Sustainability 2019, 11, x FOR PEER REVIEW 11 of 16 adaptiveSustainability thermal 2019, 11, model x FOR PEER (22.7 REVIEW◦C–29.7 ◦C). The percentage of time for cooling dropped by a staggering11 of 16 acceptableratio of 97%, thermal 92%, 96%, comfort and 92%in summer for the CB,months InsBV, including InsRBV, andnatural InsCB, ventilation respectively. (cool These air at could night), be suitableeasilyacceptable achieved clothes, thermal by drinking small comfort extra more in actions summerwater, taken and months by shad the occupantsingincluding to prevent tonatural restore the ventilation thedirect acceptable sun (coolfrom thermal airentering at comfortnight), the building.insuitable summer clothes, months drinking including more natural water, ventilation and shad (cooling to air prevent at night), the suitable direct clothes,sun from drinking entering more the water,building.The and adaptive shading thermal to prevent comfort the direct limits sun applied from enteringfor the air-conditioning the building. system reduced the total numberThe of adaptive hours required thermal for comfort artificial limits heating applied and/or for the cooling air-conditioningair-conditioning from 5139, system4498, 4476, reduced and the3805 total to 2623,number 2499, of 2119, hours and requiredrequired 1921 h forperfor artificialyearartificial for the heatingheating CB, InsB and/orand/orV, InsRBV, cooling and from InsCB, 5139, respectively, 4498, 4476, as and shown 3805 in to Figure2623, 2499, 7 and 2119, Figure and 8. 1921 This h means per year that for for the the the total CB, CB, energy InsB InsBV,V, consumptionInsRBV, and InsCB,needed respectively, for cooling and as shown heating in wasFiguresFigure also 77 significant. andand 8Figure. This 8. means This means that the that total the energy total energy consumption consumption needed needed for cooling for cooling and heating and heating was alsowas significant.also significant.

Figure 7. Number of hours required for heating or cooling using air-conditioning and the adaptive Figure 7. Number of hours required for heating or cooling using air-conditioning and the adaptive thermalFigure 7.comfort Number approach. of hours required for heating or cooling using air-conditioning and the adaptive thermal comfortcomfort approach.approach. 1000 1000 Jan 900 Jan 900 Feb 800 Feb 800 Mar 700 Mar 700 Apr 600 Apr 600 May 500 May 500 Jun 400 Jun 400 Jul Jul 300 Aug 300 Aug 200 Sep 200 Sep 100 Oct 100 Oct Numnber of hours heating or cooling required heating or cooling of hours Numnber 0 Nov Numnber of hours heating or cooling required heating or cooling of hours Numnber 0 CB InsCB InsBV InsRBV CB InsCB InsBV InsRBV Nov CB InsCB InsBV InsRBV CB InsCB InsBV InsRBV Dec Adaptive thermal limits Air-conditioning limits Dec Adaptive thermal limits Air-conditioning limits

FigureFigure 8. 8. NumberNumber of of hours hours required required for for heating heating or or cooling cooling using using air-conditioning air-conditioning and and the the adaptive adaptive thermalthermalFigure 8.comfort comfort Number approach approach of hours for for required each each month. month. for heating or cooling using air-conditioning and the adaptive thermal comfort approach for each month. DuringDuring the the winter winter months months in in the the Southern Southern Hemi Hemispheresphere (April (April to to October), October), the the adaptive adaptive thermal thermal comfortcomfortDuring limitslimits the requiredrequired winter amonths slightlya slight in higherly the higher Southern amount amount Hemi of time sphereof wheretime (April where heating to October),heating was required wasthe adaptive whenrequired compared thermal when comparedcomfort limits with therequired air-conditioning a slightly limits higher due amount to the lower of time adaptive where thermal heating comfort was requiredlimit of 19.6 when °C whencompared compared with the with air-conditioning 18 °C for the air-conditioning limits due to th elimits. lower While adaptive for thermalthe cooling comfort loads, limit the ofadaptive 19.6 °C thermalwhen compared comfort limits with 18significantly °C for the reducedair-conditioning the numb limits.er of hoursWhile where for the cooling cooling was loads, required the adaptive due to thermal comfort limits significantly reduced the number of hours where cooling was required due to Sustainability 2019, 11, 328 12 of 16 with the air-conditioning limits due to the lower adaptive thermal comfort limit of 19.6 ◦C when Sustainability 2019, 11, x◦ FOR PEER REVIEW 12 of 16 comparedSustainability with2019, 11 18, x CFOR for PEER the air-conditioningREVIEW limits. While for the cooling loads, the adaptive thermal12 of 16 comfort limits significantly reduced the number of hours where cooling was required due to the the higher upper limit which reached almost 29.7 °C in January while the air-conditioning upper higherthe higher upper upper limit limit which which reached reached almost almost 29.7 ◦29.7C in °C January in January while while the air-conditioning the air-conditioning upper upper limit limit temperature required cooling at 24 °C, which required cooling most of the summer months as temperaturelimit temperature required required cooling cooling at 24 ◦ atC, 24 which °C, which required required cooling cooling most of most the summerof the summer months months as shown as shown in Figure 9 and Figure 10. inshown Figures in 9Figure and 10 9. and Figure 10.

Figure 9. Number of hours of heating required during the winter months. Figure 9. Number of hours of heating requiredrequired duringduring thethe winterwinter months.months.

Figure 10. Number of hours of cooling required during the summer months. Figure 10. Number of hours of cooling required duringduring thethe summersummer months.months. ComparingComparing thethe averageaverage hours hours required required for for heating heating and coolingand cooling showed showed that the that monthly the monthly average Comparing the average hours required for heating and cooling showed that the monthly averagetime for time the for adaptive the adaptive thermal thermal limits limits was was almost almost half half that that of of the the average average monthly monthly time time forfor the the average time for the adaptive thermal limits was almost half that of the average monthly time for the air-conditioningair-conditioning limits limits where where it it was was 160 160 h h per per mo monthnth for for InsRBV InsRBV and and reached reached a a peak peak of of 220 220 h h per per air-conditioning limits where it was 160 h per month for InsRBV and reached a peak of 220 h per monthmonth for for the the CB CB module module while while for for the the air-conditioning air-conditioning limits, limits, it it ranged ranged from from 320 320 h h for for InsRBV InsRBV to to up up month for the CB module while for the air-conditioning limits, it ranged from 320 h for InsRBV to up 430430 h h per month for the CB module. These also also a appliedpplied to the standard deviation which indicated 430 h per month for the CB module. These also applied to the standard deviation which indicated thatthat the datadata pointspoints were were spread spread out out over over a wider a wider range range of values of values for the for air-conditioning the air-conditioning limits limits when that the data points were spread out over a wider range of values for the air-conditioning limits whencompared compared with the with adaptive the adaptive thermal thermal limits limits as shown as shown in Figure in Figure 11. 11. when compared with the adaptive thermal limits as shown in Figure 11. Sustainability 2019, 11, 328 13 of 16 Sustainability 2019, 11, x FOR PEER REVIEW 13 of 16

Average/month 450 STD 400 350 300 250 200 150 100 50 0

Number of hours heating or cooling required cooling or heating hours of Number CB InsCB InsBV InsRBV CB InsCB InsBV InsRBV Adaptive thermal limits Air-conditioning limits

FigureFigure 11.11. MonthlyMonthly averageaverage andand standardstandard deviationsdeviations forfor eacheach module.module.

UsingUsing the the adaptive adaptive thermal thermal comfort comfort limits overlimits a fixed over thermostat a fixed settingthermostat used bysetting the air-conditioning used by the systemsair-conditioning gives the systems occupants gives the chancethe occupants to control the their chance environment to control andtheir use environment low energy and solutions use low to obtainenergy and solutions sustain to their obtain thermal and sustain comfort. their These thermal measures comfort. will These ultimately measures reduce will the ultimately overall heating reduce andthe overall cooling heating energy requirements.and cooling energy requirements. 4. Conclusions 4. Conclusions The thermal comfort model has a direct impact on the prediction of the operational heating The thermal comfort model has a direct impact on the prediction of the operational heating and and cooling loads for the buildings. Using the adaptive thermal approach adjusts the comfortable cooling loads for the buildings. Using the adaptive thermal approach adjusts the comfortable temperature ranges for an air-conditioning system, thus saving significant amounts of energy. temperature ranges for an air-conditioning system, thus saving significant amounts of energy. The The occupants have more options to adjust their desired thermal comfort by using easy actions occupants have more options to adjust their desired thermal comfort by using easy actions such as such as ventilation, suitable clothes, and opening windows instead of using energy. The adaptive ventilation, suitable clothes, and opening windows instead of using energy. The adaptive thermal thermal comfort model saves more energy in buildings that are naturally ventilated when compared to comfort model saves more energy in buildings that are naturally ventilated when compared to air air conditioned buildings as residents adjust to wider indoor temperatures than the peripheral thermal conditioned buildings as residents adjust to wider indoor temperatures than the peripheral thermal comfort zones determined by the PMV model. The PMV model also presumes that residents will comfort zones determined by the PMV model. The PMV model also presumes that residents will believe that it is hotter than it really is, which gives the air-conditioning units false data to reduce believe that it is hotter than it really is, which gives the air-conditioning units false data to reduce operative temperatures and ultimately increases energy consumption. operative temperatures and ultimately increases energy consumption. There are issues associated with using the fixed temperature settings for an air-conditioning There are issues associated with using the fixed temperature settings for an air-conditioning system, for example, the system activated cooling mode in winter for the InsBV module when the system, for example, the system activated cooling mode in winter for the InsBV module when the temperature exceeded 24 ◦C. This accelerated the rate of valuable energy lost and the heating was temperature exceeded 24 °C. This accelerated the rate of valuable energy lost and the heating was required after a few hours to compensate for the heat lost during the cooling mode. This resulted in required after a few hours to compensate for the heat lost during the cooling mode. This resulted in higher energy requirements for the InsBV module when compared with the other modules despite its higher energy requirements for the InsBV module when compared with the other modules despite good performance in winter days. its good performance in winter days. The fixed temperature used by air-conditioning systems to maintain thermal comfort inside The fixed temperature used by air-conditioning systems to maintain thermal comfort inside the the modules significantly increased the overall energy usage, especially in the summer season. modules significantly increased the overall energy usage, especially in the summer season. This was This was due to the setting of a cut-off point at 22 ◦C on hot summer days, which required a massive due to the setting of a cut-off point at 22 °C on hot summer days, which required a massive amount amount of energy to reach that point. However, the adaptive thermal comfort approach allowed for of energy to reach that point. However, the adaptive thermal comfort approach allowed for a a broader range of temperatures (23 ◦C–30 ◦C) and required a little amount of energy for the occupants’ broader range of temperatures (23 °C–30 °C) and required a little amount of energy for the thermal comfort. occupants’ thermal comfort. TheThe adaptiveadaptive thermalthermal comfortcomfort decreaseddecreased thethe requirementrequirement forfor heatingheating oror coolingcooling byby almostalmost 50%50% ofof thethe timetime whenwhen comparedcompared withwith thethe fixedfixed settingssettings ofof temperaturetemperature limitslimits forfor air-conditioningair-conditioning units.units. ThisThis maymay ultimately ultimately lead lead to to reduced reduced energy energy consumption, consumption, running running costs, costs, and aand reduction a reduction of the of GHG the overGHG the over lifecycle the lifecycle of the building.of the building. Sustainability 2019, 11, 328 14 of 16

Author Contributions: Conceptualization, A.A. and D.A.; Methodology, A.A. and D.A.; Validation, A.A. and D.A.; Formal analysis, A.A.; Investigation, A.A. and D.A.; Resources, A.A. and D.A.; Data curation, A.A. and D.A.; Writing, A.A.; Preparation, A.A., D.A., A.P. and B.M.; Writing—review and editing, A.A., D.A., A.P. and B.M.; Visualization, A.A., D.A., A.P. and B.M.; Supervision, A.A., D.A., A.P. and B.M.; Project administration, A.A., D.A., A.P. and B.M.; Funding acquisition, A.A., D.A., A.P. and B.M. Funding: This research received no external funding. Conflicts of Interest: The authors declare no conflicts of interest.

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