Energy Modelling of Traditional and Contemporary Mosque Buildings in Oman

buildings

Article Energy Modelling of Traditional and Contemporary Mosque Buildings in Oman

Haitham Al Rasbi * and Mohamed Gadi

Department of Architecture and the Built Environment, University of Nottingham, Nottingham NG7 2RD, UK; [email protected] * Correspondence: [email protected] or [email protected]

Abstract: Building energy efﬁciency is vital to achieve human thermal comfort with minimum energy consumption. It is a great concern in extremely hot countries such as Oman. This study aims to investigate the thermal performance of contemporary mosque buildings in comparison to traditional mosque buildings in Oman. The research methodology employs energy modelling using EDSL’s Tas Engineering computer simulation software. The analysis focused on how traditional mosque buildings compare to contemporary mosque buildings in terms of dry bulb air temperature and different thermal loads. The outcome showed the traditional mosque building design and construction are better suited for free-running buildings, while contemporary mosque building design and construction achieved less cooling load demand per area.

Keywords: thermal performance; energy modelling; vernacular architecture; mosques; traditional buildings

Citation: Al Rasbi, H.; Gadi, M. 1. Introduction Energy Modelling of Traditional and Sustainability and energy efﬁciency have vast global interest due to the continuously Contemporary Mosque Buildings in increasing pollution and energy consumption. It is not imaginable now to live without Oman. Buildings 2021, 11, 314. electricity and air conditioning. Air conditioning is the most energy demanding use https://doi.org/10.3390/ in buildings in most countries, and it is continuing to increase every year [1]. Oman buildings11070314 features an extremely hot and arid climate with a maximum temperature recorded of about 50.7 ◦C and relative humidity that can be very high (100%) in coastal areas and very low Academic Editor: Elena Lucchi (1%) in interior desert areas [2]. The building’s sector consumes about 75% of the total energy consumption in the country according to The Authority of Electricity Regulation Received: 30 June 2021 in Oman [3]. Air conditioning accounts for most the energy consumed by the building’s Accepted: 17 July 2021 Published: 20 July 2021 sector [4]. This research aims to investigate the thermal performance in buildings in Oman

Publisher’s Note: MDPI stays neutral taking a traditional mosque and a contemporary mosque as two case studies. Mosque with regard to jurisdictional claims in architecture is unique, but also simple, which makes it an interesting study. Mosque published maps and institutional affil- architecture is simple given its shape and layout is typical to mosques in general, but it is iations. unique given its daily intermittent usage. The Sultanate of Oman features both recently built mosques and traditional 600-year-old mosques. It is estimated that there are 16,000 mosques across Oman [5]. Contemporary mosques rely on active cooling systems, while some traditional mosques still feature passive cooling systems. The materials used in the construction of contemporary and traditional mosques are different. The general layout Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. and design, however, has stayed mostly the same between old and new mosques [6]. This article is an open access article Improving the energy efficiency of mosques could contribute to much needed reduction of distributed under the terms and energy consumption. It could also contribute towards energy efficiency of other buildings conditions of the Creative Commons since any techniques employed in the typical simple design of mosques can be potentially Attribution (CC BY) license (https:// replicated into other buildings. creativecommons.org/licenses/by/ In 2017, Oman has put forward the 2040 vision. It outlines the 13 top priorities of 4.0/). the country to be achieved by 2040 which are called the “National Priorities”. Two of

Buildings 2021, 11, 314. https://doi.org/10.3390/buildings11070314 https://www.mdpi.com/journal/buildings Buildings 2021, 11, 314 2 of 20

the National Priorities are the “Sustainable Development in Governorates and cities” and “Natural Resources and Environmental Sustainability” [7]. This research also aims to contribute to both these National Priorities. A more energy efficient mosque building would contribute towards a more sustainable city and environment. Another significance to this research is the fact that electricity is still subsidised for most buildings in Oman as of 2021. This is changing very soon though. On 20 December 2020, it was announced that electricity subsidies will be phased out over a period of five years starting from 2021 in Oman [8]. This will put a greater emphasis on sustainable design and energy efficiency research for all types of buildings in Oman. Another aspect of this research is the impact of vernacular architecture in building’s thermal comfort and performance. There were several studies conducted to investigate how thermal comfort is achieved in vernacular buildings in Oman. There are features that improved the thermal comfort of old buildings and could potentially apply to new buildings. Compact patterns of settlement and courtyards are two examples from the vernacular architecture in Oman that could improve thermal comfort in buildings [6]. Since Oman’s mass modernisation in 1970, it began to depend on active air conditioning systems, which made buildings built afterwards less efficient. Buildings built before this period were built to achieve thermal comfort using passive means. Passive thermal comfort was achieved by building’s design, orientation, and construction materials [9]. This research focuses more on the thermal performance aspect of mosque buildings in Oman. A building can be considered as a thermal system with thermal energy inputs and outputs. The environment, the building itself, and occupants all contribute to the heat inputs and outputs [10]. The environment in Oman features hot and arid climate. Two of the most significant building thermal performance factors when focusing on hot-arid climate are solar gain and conduction through the building envelope [11]. Taking the surrounding environment into account, state-of-the-art research in energy efficiency indicates that there are many techniques that could be employed to significantly reduce cooling load [12]. Fenestration, building envelope insulation, building material, and thermostat set point are believed to be areas for potential improvement in buildings in hot arid regions [13]. Fenestration can be argued as the weakest element in a building. Controlling the window-to-wall ratio (or glazing ratio) is key to achieve higher building efficiency. A study conducted in mosques in Saudi Arabia concluded that the optimal value for glazing ratio is around 15% overall [14]. It is also recommended to decrease the U-value of the building envelope to limit thermal transmittance into the building. Increasing the thermostat set point also yields considerable savings in cooling loads. As per a study conducted on mosques in Kuwait, an electrical energy saving of 10% was achieved by increasing the thermostat temperature by 1 ◦C[15]. In another study conducted on government buildings of Oman, it concluded that increasing the set point by 3 ◦C yielded annual energy savings of at least 13.23% [16].

Research Objective The research objective is to contribute to the energy efﬁciency in buildings research. It takes two different mosques as case studies. One is a contemporary mosque (built in 2016), and the other is a traditional mosque (about 400 years old). This will help create a better understanding of the thermal performance status of both new and old mosques. It is interesting to see the effect of air conditioning in traditional old buildings in comparison with contemporary buildings. A 400-year-old building witnessed generations of usage in addition to continuous renovation and modiﬁcations. On the other hand, a recently built mosque is relatively new and is built to the current standard of construction. Comparing the thermal performance of the two mosques could help us understand the areas for improvement in a contemporary building’s thermal performance. It could also help us understand the unique and sustainable features of a vernacular building that do not exist anymore in a modern building today. BuildingsBuildings 2021 2021, 11, 11, x, FORx FOR PEER PEER REVIEW REVIEW 3 3of of 20 20

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MostMost of of the the air air conditioning conditioning consumption consumption in in Oman Oman occurs occurs during during the the summer, summer, when when external temperature reaches a maximum of 50 °C. During the winter, dry bulb air tem‐ externalMost temperature of the air conditioning reaches a maximum consumption of 50 in °C. Oman During occurs the duringwinter, the dry summer, bulb air when tem‐ perature varies between different regions of Oman. In Muscat, it ranges between 15 and peratureexternal temperaturevaries between reaches different a maximum regions of of Oman. 50 ◦C. In During Muscat, the it winter, ranges dry between bulb air 15 tem-and 30 °C [2]. Most people are comfortable with natural ventilation without the use of air con‐ 30perature °C [2]. variesMost people between are different comfortable regions with of natural Oman. ventilation In Muscat, without it ranges the between use of air 15 con and‐ ditioning30ditioning◦C[2]. during Mostduring peoplethe the winter. winter. are comfortable with natural ventilation without the use of air conditioningThisThis research research during aims aims the to winter. to analyse analyse the the mosques mosques performance performance between between winter winter and and summer summer consideringconsideringThis research internal internal aims dry dry to bulb bulb analyse temperature, temperature, the mosques relative relative performance humidity, humidity, between external external winter dry dry bulb bulb and tempera summertempera‐ ‐ ture,consideringture, and and cooling cooling internal loads. loads. dry Breakdown bulbBreakdown temperature, of of the the different relativedifferent humidity,loads loads are are also external also analysed analysed dry bulb such such tempera- as as solar solar gain,ture,gain, andbuilding building cooling heat heat loads. transfer, transfer, Breakdown and and heat heat of conduction conduction the different gain. gain. loads are also analysed such as solar gain,The buildingThe research research heat attempts attempts transfer, to and to answer answer heat conductionthe the following following gain. questions: questions:   WhichTheWhich research type type of attemptsof mosques mosques to perform answerperform better the better following in in Oman Oman questions: (contemporary (contemporary or or traditional)? traditional)? •  HowWhichHow does does type building ofbuilding mosques performance performance perform betterchange change in between Omanbetween (contemporary winter winter and and summer? summer? or traditional)? •  HowHow doesmuch much building cooling cooling performanceload load reduction reduction change in in both both between cases cases can winter can be be andachieved achieved summer? utilizing utilizing state state‐of‐of‐ ‐ • theHowthe‐art‐art much passive passive cooling energy energy load saving saving reduction techniques? techniques? in both cases can be achieved utilizing state-of-the- art passive energy saving techniques? 2.2. Methodology Methodology 2. Methodology AA building building energy energy modelling modelling and and computer computer simulation simulation can can serve serve many many purposes purposes ei ei‐ ‐ therther forA for building the the construction construction energy modelling industry industry or and or research. research. computer It It is simulation is imperative imperative can for for serve all all stakeholders manystakeholders purposes involved involved either inforin the thethe building construction building simulation simulation industry process orprocess research. to to agree agree It is imperativeon on a aperformance performance for all stakeholders criterion criterion with with involved defined defined in measures.themeasures. building Once Once simulation the the simulation simulation process tois is agreedone, done, onthe the a results performance results can can be be criterion benchmarked benchmarked with defined against against measures. the the per per‐ ‐ formanceOnceformance the measures simulation measures to to is arrive arrive done, to to the a aset set results of of recommendations recommendations can be benchmarked to to the the stakeholders against stakeholders the performance of of the the build build‐ ‐ ingmeasuresing [17]. [17]. to arrive to a set of recommendations to the stakeholders of the building [17]. ThereThereThere are are aa wideawide wide range range range of of softwareof software software specialized specialized specialized for for thermalfor thermal thermal comfort comfort comfort such such such as EDSL’sas as EDSL’s EDSL’s Tas TasEngineering,Tas Engineering, Engineering, IES VE,IES IES VE, Ecotect, VE, Ecotect, Ecotect, EnergyPlus, EnergyPlus, EnergyPlus, and and Design and Design Design Builder. Builder. Builder. The researchThe The research research methodology method method‐ ‐ ologyemployedology employed employed in this in researchin this this research research is Tas is Engineering is Tas Tas Engineering Engineering software, software, software, an energy an an energy energy computer computer computer simulation simu simu‐ ‐ lationsoftware.lation software. software. Tas Engineering Tas Tas Engineering Engineering software software software specializes specializes specializes in simulation in in simulation simulation of dynamic of of dynamic dynamic thermal thermal perfor-thermal performancemanceperformance of buildings of of buildings buildings and their and and systems. their their systems. Itsystems. uses a 3DIt It uses modeluses a a3D and 3D model integratesmodel and and itintegrates withintegrates natural it itwith andwith forced air flow along with HVAC systems to estimate energy demand and resulting internal naturalnatural and and forced forced air air flow flow along along with with HVAC HVAC systems systems to to estimate estimate energy energy demand demand and and temperatures and humidity. It accounts for dynamic parameters such as air flow as well as resultingresulting internal internal temperatures temperatures and and humidity. humidity. It It accounts accounts for for dynamic dynamic parameters parameters such such static parameters such as building material thermal capacity [18]. Tas Engineering software asas air air flow flow as as well well as as static static parameters parameters such such as as building building material material thermal thermal capacity capacity [18]. [18]. Tas Tas was utilized for this research because it is deemed most suitable for the purposes of this EngineeringEngineering software software was was utilized utilized for for this this research research because because it itis is deemed deemed most most suitable suitable for for research. It is simple and provide sufficient tools to study the different areas of mosque thethe purposes purposes of of this this research. research. It It is is simple simple and and provide provide sufficient sufficient tools tools to to study study the the different different buildings’ thermal properties [19,20]. It was utilized to study two mosque buildings from areasareas of of mosque mosque buildings’ buildings’ thermal thermal properties properties [19,20]. [19,20]. It It was was utilized utilized to to study study two two mosque mosque two different eras in Oman. buildingsbuildings from from two two different different eras eras in in Oman. Oman. Table1 shows the details of the two mosques selected for this research. By energy TableTable 1 1shows shows the the details details of of the the two two mosques mosques selected selected for for this this research. research. By By energy energy modelling both types of mosques, the comparison could lead to possibilities of using old modellingmodelling both both types types of of mosques, mosques, the the comparison comparison could could lead lead to to possibilities possibilities of of using using old old methods in new buildings to achieve a more sustainable building. Additionally, it could methods in new buildings to achieve a more sustainable building. Additionally, it could methodshelp make in recommendations new buildings to achieve implementable a more insustainable different typesbuilding. of buildings Additionally, not restricted it could help make recommendations implementable in different types of buildings not restricted helpto mosques. make recommendations implementable in different types of buildings not restricted toto mosques. mosques. Table 1. A list of mosques for the case study. TableTable 1. 1. A A list list of of mosques mosques for for the the case case study. study. Maximum Typical Year Mosque’s Picture Mosque’s Name Location YearYear AreaMaximumMaximum NumberNumber Number of of of Typical TypicalNumber Number Number of Zones (Area) Mosque’sMosque’s Picture Picture Mosque’sMosque’s Name Name LocationLocation Built AreaArea ZonesZones (Area) (Area) BuiltBuilt WorshippersWorshippersWorshippers ofof Worshippers Worshippers

2 HudhayfahHudhayfahHudhayfah Bin Bin 11201120 ZoneZoneZone 1 (906(9061 (906 m m2 )m2) ) Muscat,Muscat,Muscat, Oman Oman Oman 20152015 2015 1120 m2 11001100 1100 150 150150 AlyamanAlyamanAlyaman Mosque Mosque Mosque mm2 2 ZoneZoneZone 2 (174(1742 (174 m m2 )m2) 2)

2 ZoneZoneZone 1 (278(2781 (278 m m )m2) 2) AlAl Wafi, Wafi,Al Al Wafi,Al Kamil Kamil Al 2 Zone 2 (168 m )2 2 Kamil Wal Wafi, 2 ZoneZone 2 (1682 (168 m m) ) Al Wafi mosque 1600 s 4702 2 m 350 60 Zone 3 AlAl Wafi Wafi mosque mosque Wal Wal Wafi, Wafi,Oman Oman Oman (250 (250 km (250 1600 1600 s s 470470 m m 350350 6060 Zone-courtyard-Zone 3 ‐ 3court ‐court‐ ‐ kmkm from fromfrom Muscat) Muscat) 2 yardyard(212‐ (212‐ m(212) m m2) 2)

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2.1. Computer Simulation The computer simulation process via EDSL’s Tas Engineering software (version 9.5.1, Environmental Design Solutions Ltd, Milton Keynes, United Kingdom) consist of: 3D modelling the building, setting the location and weather data, assignment of construction materials, setting internal gains and conditions, building thermal simulation, and simulation results analysis.

2.2. Calendar Muscat and Al Waﬁ’s climate features two seasons throughout the year: summer and winter. For the purposes of this simulation, it was considered that the winter season spanned from 1 November until 28 February, while the rest was considered summer season. The buildings for this simulation were free running during the winter season and air-conditioned during the summer season.

2.3. Weather Data The weather data for both the Hudhayfah mosque and Al Waﬁ mosque were Typical Metrological Years (TMY) ﬁles in EPW weather format for Muscat International Airport region. The weather data was derived from the period 2004 to 2018 [21].

2.4. Orientation All mosques are oriented towards the Qiblah (Direction towards the Kabaah), which makes both Hudhayfah and Al Waﬁ mosques’ orientation towards the west [13].

2.5. Height Hudhayfah mosque’s prayer hall ceiling height is about 4.2 metres and its Qubba’s (Dome’s) ceiling height reaches 9 metres, while Al Waﬁ mosque’s prayer hall ceiling height ranges between 3.5 and 6.5 metres since it has an arched roof.

2.6. Age of Building The Hudhayfah mosque was built in 2015, while the Al Waﬁ mosque was built in the 1600s. The Al Waﬁ mosque was renovated several times throughout its history. A major restoration was done in 1989 [22].

2.7. Fenestration The Hudhayfah mosque uses windows with aluminium frames, while the Al Waﬁ mosques has windows with timber frames. All windows considered are double-glazed.

2.8. Internal Gains Air conditioning is used throughout the year except the winter season. Some buildings in Oman have cooling air conditioning active even during the winter [16]. For the purposes of this research, both mosque buildings are considered free running during the winter season (from 1 November until 28 February). During the rest of the calendar the air conditioning is used for cooling only. Mosques are used intermittently, ﬁve times a day. The air-conditioning runs for two periods. The ﬁrst period is from 3 am till 5 am for the fajr prayer. The second period covers four prayer congregation times, which is from 12 pm until 9 pm. Table2 shows the typical daily prayer times during the day. Each prayer lasts for about 30 min, except for Friday congregational prayer which lasts for about 90 min [23]. Buildings 2021, 11, 314 5 of 20

Buildings 2021, 11, x FOR PEER REVIEW 5 of 20 Table 2. Daily prayer times in Muscat, Oman [24].

Prayer Sequence Prayer Start Time Range Prayer Name Time Held duringFirst prayer the Day Fajr Prayer Before sunrise (Varies3:52 Throughout am–5:32 am the Year) SecondFirst prayer prayer Dhuhr Fajr Prayer Prayer BeforeAt noon sunrise 11:55 3:52 am–12:26 a.m.–5:32 a.m.pm SecondThird prayer prayer DhuhrAsr prayer Prayer Afternoon At noon 11:553:04 pm–3:45 a.m.–12:26 pm p.m. FourthThird prayer prayer Maghrib Asr prayer prayer After Afternoon sunset 5:24 3:04 pm–7:03 p.m.–3:45 pm p.m. Fourth prayer Maghrib prayer After sunset 5:24 p.m.–7:03 p.m. FifthFifth prayerprayer IshaIsha prayer prayer Night Night-time‐time 6:39 6:39 pm–8:25 p.m.–8:25 pm p.m.

2.9. Cooling 2.9. Cooling The Hudhayfah mosque has a DX roof top packaged units for air conditioning, while The Hudhayfah mosque has a DX roof top packaged units for air conditioning, while Al Wafi mosque utilizes a DX split unit system [4]. It is noted that according to a survey Al Waﬁ mosque utilizes a DX split unit system [4]. It is noted that according to a survey conducted most occupants in residential buildings preferred a thermostat setpoint be‐ conducted most occupants in residential buildings preferred a thermostat setpoint between tween 20 and 22 °C [25], while the government buildings’ thermostat setpoint is around 20 and 22 ◦C[25], while the government buildings’ thermostat setpoint is around 22 ◦C[16]. On22 °C the [16]. other On hand, the other 24 ◦C hand, is considered 24 °C is considered to be the optimal to be the thermostat optimal thermostat set point to set achieve point thermalto achieve comfort thermal according comfort toaccording a pilot measurement to a pilot measurement study in Oman study [ 26in]. Oman For the [26]. purposes For the ofpurposes this simulation, of this simulation, the thermostat the thermostat setpoint setpoint for the air-conditioning for the air‐conditioning system issystem set for is anset upperfor an upper limit of limit 23 ◦ ofC and23 °C is and set foris set cooling for cooling from from 1 March 1 March to 31 to October. 31 October. The buildingsThe buildings are consideredare considered as naturally as naturally ventilated ventilated for the for restthe ofrest the of year. the year. HudhayfahHudhayfah mosque’smosque’s DX roofroof toptop packagedpackaged unitunit introducesintroduces 10%10% freshfresh air,air, whilewhile AlAl WaﬁWafi mosque’s mosque’s DX DX split split unit unit system system does does notnot introduceintroduce freshfresh air.air. For For the the purposes purposes ofof thisthis research,research, itit isis assumedassumed thatthat bothboth mosquesmosques havehave 0.5 0.5 air air changes changes per per hour. hour.

2.10.2.10. Climate Conditions ofof MuscatMuscat andand AlAl WafiWafi BothBoth MuscatMuscat and and Al Al Wafi Wafi are are classified classified as as hot hot and and dry dry according according to to the the Köppen–Geiger Köppen–Gei‐ climateger climate classification. classification. [27 ].[27]. Muscat Muscat is a is hot a hot climate climate city city which which is is located located by by the the coastline coastline ofof GulfGulf ofof Oman.Oman. ItIt featuresfeatures longlong summerssummers andand shortshort warmwarm winterswinters [[28].28]. AlAl WafiWafi villagevillage isis locatedlocated 250250 kilometreskilometres awayaway fromfrom Muscat,Muscat, whichwhich featuresfeatures aa similarsimilar climateclimate toto Muscat.Muscat. ForFor thethe purposespurposes ofof thisthis research,research, MuscatMuscat weatherweather datadata waswas inputinput intointo thethe simulationssimulations ofof bothboth mosques’mosques’ buildings.buildings. Figure 11 shows shows the the location location of of Muscat Muscat and and Al Al Wafi. Wafi. Figure Figure2 2 showsshows meanmean temperatures temperatures and and humidity humidity throughout throughout a a typical typical year, year, while while Figure Figure3 shows 3 shows a bioclimatica bioclimatic chart chart for for Muscat. Muscat. Figure Figure3 shows3 shows the the bioclimatic bioclimatic chart chart that that most most months months have have ◦ ambientambient airair temperaturetemperature aboveabove 3030 °C.C. TheThe greengreen areaarea isis thethe comfort comfort zonezone areaarea underunder airair conditioning,conditioning, which which makes makes 20 20 to to 24 24 thermostat thermostat set set point point reasonably reasonably within within the comfort the comfort zone zoneif humidity if humidity is between is between 30% and 30% 80%. and 80%.

FigureFigure 1.1. AA mapmap showingshowing thethe locationlocation ofof MuscatMuscat citycity andand AlAl WaﬁWafi village. village. Buildings 2021, 11, 314 6 of 20 Buildings 2021, 11, x FOR PEER REVIEW 6 of 20 Buildings 2021, 11, x FOR PEER REVIEW 6 of 20

40 80 40 80 35 70 3035 70 2530 60 25 60 20 50 1520 50 1015 40 10 40 5 30 Temperature (°C) 5 30 Temperature (°C) 0 0 20 20

Relative Humidity (%) 10

Relative Humidity (%) 10 0 0 July May June April July

Mean High Air Temperature Mean Air Temperature May June April March Mean High Air Temperature Mean Air Temperature August January March October August February January October December February

Mean Low Air Temperature November September December

Mean Low Air Temperature November September (a) (b) (a) (b) Figure 2. (a) Mean ambient air temperature in a typical year in Muscat, Oman. (b) Mean relative humidity in a typical year Figure 2. (a) Mean ambient air temperature in a typical year in Muscat, Oman. (b) Mean relative humidity in a typical year in Muscat, Oman. inin Muscat,Muscat, Oman.Oman.

Figure 3. Bioclimatic chart for Muscat. Solid lines are for months from normal Typical Metrological FigureFigure 3.3. Bioclimatic chart for Muscat. Solid lines are for months from normal Typical MetrologicalMetrological Years (TMY), while dashed lines are for months from TMY developed for passive cooling [29,30]. YearsYears (TMY),(TMY), while while dashed dashed lines lines are are for for months months from from TMY TMY developed developed for for passive passive cooling cooling [ 29[29,30].,30]. 3. Design and Construction Details of Hudhayfah and Al Wafi Mosques 3.3. Design and Construction Details of Hudhayfah andand AlAl WafiWafi Mosques Mosques 3.1. Hudhayfah Mosque 3.1.3.1. Hudhayfah Mosque The Hudhayfah bin Al Yaman Mosque was built in 2015 in Muscat, the capital of the The Hudhayfah bin bin Al Al Yaman Yaman Mosque Mosque was was built built in in 2015 2015 in inMuscat, Muscat, the the capital capital of the of Sultanatethe Sultanate of Oman. of Oman. The area The is area 1120 is m 11202 and m 2fitsand a maximum fits a maximum of 1100 of worshippers. 1100 worshippers. Figure Sultanate of Oman. The area is 1120 m2 and fits a maximum of 1100 worshippers. Figure 4Figure shows4 showsthe Hudhayfah the Hudhayfah mosque mosque ground ground floor plan floor drawing, plan drawing, and the and ground the ground floor floorplan 4 shows the Hudhayfah mosque ground floor plan drawing, and the ground floor plan planmodelled modelled into intothe Tas the Tassoftware. software. Figures Figures 5 and5 and 6 6show show different different 3D views fromfrom the the Tas Tas modelled into the Tas software. Figures 5 and 6 show different 3D views from the Tas software as well as an east elevation view. It can be noticed that the southern wall misses software as well as an east elevation view. It can be noticed that the southern wall misses three windows in the Tas model as thisthis isis thethe case inin built mosque. The Tas model showsshows three windows in the Tas model as this is the case in built mosque. The Tas model shows the mihrab (the(the semi-circularsemi‐circular niche niche in in the the mosque’s mosque’s western western wall wall indicating indicating the the direction direction of the mihrab (the semi‐circular niche in the mosque’s western wall indicating the direction ofthe the qibla) qibla) in thein the western western wall wall as aas square a square shape shape instead instead of a of semi-circular a semi‐circular shape shape to simplify to sim‐ of the qibla) in the western wall as a square shape instead of a semi‐circular shape to sim‐ plifythe model the model [13]. Table [13].3 Table lists the 3 lists construction the construction details of details the Hudhayfah of the Hudhayfah mosque’s mosque’s building plify the model [13]. Table 3 lists the construction details of the Hudhayfah mosque’s buildingelements. elements. It features It a features typical constructiona typical construction detail found detail in mostfound recent in most buildings recent buildings in Oman. building elements. It features a typical construction detail found in most recent buildings Buildings 2021, 11, x FOR PEER REVIEW 7 of 20

Buildings 2021, 11, x FOR PEER REVIEW 7 of 20

Buildings 2021, 11, x FOR PEER REVIEW 7 of 20 in Oman. A typical window size in Hudhayfah mosque is 1.9 metres by 2.54 metres, while a typical door is 2.4 metres wide by 3 metres high. Buildings 2021, 11, 314 in Oman. A typical window size in Hudhayfah mosque is 1.9 metres by 2.54 metres,7 of 20while a typical door is 2.4 metres wide by 3 metres high. in Oman. A typical window size in Hudhayfah mosque is 1.9 metres by 2.54 metres, while Aa typicaltypical window door is size 2.4 metres in Hudhayfah wide by mosque 3 metres is 1.9 high. metres by 2.54 metres, while a typical door is 2.4 metres wide by 3 metres high.

(a) (b)

Figure 4. (a) Ground(a) floor plan of Hudhayfah Mosque; (b) ground floor plan (ofb )Hudhayfah Mosque as shown in Tas software showing the two( azones.) (b) Figure 4. (a) Ground floor plan of Hudhayfah Mosque; (b) ground floor plan of Hudhayfah Mosque as shown in Tas Figure 4. (a) Ground ﬂoor plan of Hudhayfah Mosque; (b) ground ﬂoor plan of Hudhayfah Mosque as shown in Tas software showingFigure 4. the (a )two Ground zones. floor plan of Hudhayfah Mosque; (b) ground floor plan of Hudhayfah Mosque as shown in Tas softwaresoftware showing showing thethe two two zones. zones.

Figure 5. Three‐dimensional (3D) views of Hudhayfah mosque. Figure 5.Figure FigureThree 5.‐ dimensional5.Three-dimensional Three‐dimensional (3D) (3D)views (3D) views of views Hudhayfah of Hudhayfah of Hudhayfah mosque. mosque. mosque.

Figure 6. East elevation view of Hudhayfah mosque. The Qubba’s (Dome’s) maximum height is 9 metres, while the main prayer hall’s height is 4.2 metres. Figure 6. East elevation view of Hudhayfah mosque. The Qubba’s (Dome’s) maximum height is 9 metres, while the main prayerFigure hall’s 6.height East elevationis 4.2 metres. view of Hudhayfah mosque. The Qubba’s (Dome’s) maximum height is 9 metres, while the main Figure 6. East elevation view of Hudhayfah mosque. The Qubba’s (Dome’s) maximum height is 9 metres, while the main prayer hall’s height is 4.2 metres. prayer hall’s height is 4.2 metres.

Buildings 2021, 11, x FOR PEER REVIEW 8 of 20 Buildings 2021, 11, x FOR PEER REVIEW 8 of 20

Table 3. Construction details of Hudhayfah mosque. Table 3. Construction details of Hudhayfah mosque. ConstructionBuildings 2021, 11 , 314 Thickness U‐ Value Specific Heat Time Constant8 of 20 Construction Construction Detail Thickness U‐ Value Specific Heat Time Constant Type Construction Detail (mm) (W/m2.K) (J/kg.K) (hours) Type (mm) (W/m2.K) (J/kg.K) (hours) Concrete brick wall insulated with polyurethane External wall Concrete brick wall insulated with polyurethane 375 0.4 953.56 8.5 External wall Tableboard 3. Construction details of Hudhayfah375 mosque. 0.4 953.56 8.5 board Internal wall Concrete brick wall 225 2.47 904.72 3.2 Internal wall Concrete brick wall Thickness225 U-Value2.47 Speciﬁc904.72 Heat Time Constant3.2 ConstructionRoof TypeConcrete slab insulated Construction with polyurethane Detail board 265 0.8 996.35 8.3 Roof Concrete slab insulated with polyurethane board (mm)265 (W/m2·K)0.8 (J/kg996.35·K) (hours)8.3 Window frame Aluminium 60 5.9 896 0 WindowExternal wall frame Concrete brick wall insulatedAluminium with polyurethane board 37560 0.45.9 953.56896 8.5 0 DoubleInternal glazed wall Concrete brick wall 225 2.47 904.72 3.2 Double glazed 3 mm glass + 12 mm air space + 3 mm glass 21 7.8 ‐ 0 window Roofpane 3 Concrete mm glass slab insulated+ 12 mm with air polyurethanespace + 3 mm board glass 26521 0.87.8 ‐ 996.35 8.3 0 windowWindow frame pane Aluminium 60 5.9 896 0 DoorDouble frame glazed Aluminium 60 5.9 896 0 Door frame 3 mm glass + 12Aluminium mm air space + 3 mm glass 2160 7.85.9 -896 0 0 Doorwindow pane pane 3 mm glass + 12 mm air space + 3 mm glass 31 7.8 ‐ 0 Door frame pane 3 mm glass + 12 Aluminium mm air space + 3 mm glass 6031 5.97.8 ‐ 896 0 0 Door pane 3 mm glass + 12 mm air space + 3 mm glass 31 7.8 - 0 3.2. Al Wafi Mosque 3.2. Al Wafi Mosque Al Wafi Mosque is in Al Kamil and Al Wafi, about 250 km away from Muscat, Oman. It 3.2.was Al built WaﬁAl inWafi Mosque 1600s Mosque [31], andis in renovated Al Kamil and in 1989, Al Wafi, and aboutsince then 250 km there away were from minor Muscat, restora Oman.‐

tionsIt to wasAl the Wafi built Mosque Mosque in 1600s up istill[31], in date. Al and Kamil The renovated walls and vary Al in Wafi, between1989, about and 500 250since and km then 1000 away there millimetres from were Muscat, minor in thick Oman. restora‐ ‐ nessIt wastions [22]. built toIt theis in important Mosque 1600s [31 up ],to and tillmention date. renovated The that walls this in 1989, varysimulation and between since of 500Al then Wafi and there 1000Mosque were millimetres minor is as per restora- in its thick ‐ conditiontionsness to [22]. in the 2015. MosqueIt is Theimportant courtyard up till to date. mention (Zone The 3) wallsthat was this recently vary simulation between closed of 500completely, Al and Wafi 1000 Mosque but millimetres it was is as con per‐ in its sideredthicknesscondition as a [ naturally22 in]. It2015. is important ventilatedThe courtyard to open mention (Zone courtyard that 3) was this in recentlythe simulation simulations. closed of Al completely, Figures Wafi Mosque 7–9 but shows isit was as Al per con ‐ Wafiitssidered condition mosques as designa in naturally 2015. in The plans, ventilated courtyard sections, open (Zone and courtyard 3D 3) wasviews. recentlyin A the typical simulations. closed window completely, Figures size is 0.77–9 but metre shows it was Al byconsidered 1Wafi metre, mosques while as a naturallya design typical in door ventilated plans, is 1.2 sections, openmetres courtyard and width 3D byviews. in 1.8 the metres A simulations. typical height. window Figures size7– is9 shows0.7 metre Alby Wafi 1 metre, mosques while design a typical in plans, door is sections, 1.2 metres and width 3D views. by 1.8 A metres typical height. window size is 0.7 metre by 1 metre, while a typical door is 1.2 metres width by 1.8 metres height.

(a) (b) (a) (b) Figure 7. (a) Al Wafi Mosque floor plan showing zones in Tas (Reproduced from [22]); (b) 3D view of Al Wafi Mosque. FigureFigure 7. (7.a )(a Al) Al Wafi Wafi Mosque Mosque floor floor plan plan showing showing zones zones in Tasin Tas (Reproduced (Reproduced from from [22 ]);[22]); (b) ( 3Db) 3D view view of Al of WafiAl Wafi Mosque. Mosque.

Buildings 2021, 11, x FOR PEER REVIEW 9 of 20

FigureFigure 8. 8.ThreeThree-dimensional‐dimensional (3D) (3D) views views of of Al Al Wafi Waﬁ Mosque. Mosque. Figure 8. Three‐dimensional (3D) views of Al Wafi Mosque.

FigureFigure 9. North 9. North elevation elevation of ofAl Al Wafi Waﬁ Mosque. Mosque.

The construction details are shown in the Table 4 featuring clay as the main material in the building. It is common in the region for such clay walls to have a density of about 1730 kg/m3 [32]. ASHRAE 2009 handbook states that clay or adobe walls can have a con‐ ductivity that range between 0.7 to 0.85 W/m.K. for a 1730–1800 kg/m3 dense clay walls [33]. Al Wafi mosque walls decrease in thickness as it increases in height, and the thickness varies from a wall to another. This means U‐values are different at any given point across all the walls and roof of Al Wafi mosque. For the purposes of this research, it can be esti‐ mated that the walls of Al Wafi Mosque (mean thickness of 1 metre) can have a U‐value of 0.7 W/m2.K. The roof (mean thickness of 0.7 metre) is estimated to have a U‐value of 1.1 W/m2.K.

Table 4. Construction details of Al Wafi mosque.

Construction Specific Heat Time Constant Construction Detail Thickness (mm) U‐Value (W/m2.K) Type (J/kg.K) (hours) Varies between 500 Varies (average of Varies between Walls Clay/Mud wall 837 and 1200 0.7) 15 and 80 Aluminium partition wall 12 5.9 896 0 Clay/Mud roof and wood Varies between 300 Varies (average of Varies between Roof 837 beams and 750 1.1) 5.8 and 28 Window frame Timber 40 2 1632.85 0 Double glazed 3 mm glass + 12 mm air 3 7.8 ‐ 0 window pane space + 3 mm glass Door frame Timber 40 2 1632.85 0 Door pane Timber 40 2 1632.85 0

4. Results and Discussion The results in this section present data from Hudhayfah and Al Wafi mosques’ sim‐ ulations. Both mosques’ simulation results are split into winter and summer results. The winter results and summer results presented are for the winter design day in Muscat, day 20, and the summer design day in Muscat, day 179, respectively. The presented results compare between the external dry bulb temperature (DBT), internal DBT, and loads breakdown of the different zones in each mosque.

4.1. Hudhayfah Mosque Winter Simulation Results Hudhayfah mosque Zone 2′s DBT is higher than Zone 1′s DBT throughout day 20. Figure 10 shows the external DBT during the coldest day of the year, day 20, along with the DBT inside the mosque. Both zones maintain a higher DBT than external temperature throughout the day. Zone 2′s temperature is consistently higher than Zone 1 throughout the day by at least 2 °C at 07:00 and reaches to a difference of up to 6 °C at 14:00. It is also evident that Zone 2′s DBT fluctuates throughout the day similar to external DBT. Zone 2 DBT increases from 26 °C at 07:00 to 30 °C at 14:00, while Zone 1 stays within one degree Celsius from 23 °C. Buildings 2021, 11, 314 9 of 20

The construction details are shown in the Table4 featuring clay as the main material in the building. It is common in the region for such clay walls to have a density of about 1730 kg/m3 [32]. ASHRAE 2009 handbook states that clay or adobe walls can have a conductivity that range between 0.7 to 0.85 W/m·K. for a 1730–1800 kg/m3 dense clay walls [33]. Al Wafi mosque walls decrease in thickness as it increases in height, and the thickness varies from a wall to another. This means U-values are different at any given point across all the walls and roof of Al Wafi mosque. For the purposes of this research, it can be estimated that the walls of Al Wafi Mosque (mean thickness of 1 metre) can have a U-value of 0.7 W/m2·K. The roof (mean thickness of 0.7 metre) is estimated to have a U-value of 1.1 W/m2·K.

Table 4. Construction details of Al Waﬁ mosque.

Construction Speciﬁc Heat Time Constant Construction Detail Thickness (mm) U-Value (W/m2·K) Type (J/kg·K) (hours) Varies between Varies between Walls Clay/Mud wall Varies (average of 0.7) 837 500 and 1200 15 and 80 Aluminium partition wall 12 5.9 896 0 Clay/Mud roof and wood Varies between Varies between Roof Varies (average of 1.1) 837 beams 300 and 750 5.8 and 28 Window frame Timber 40 2 1632.85 0 Double glazed 3 mm glass + 12 mm air space 3 7.8 - 0 window pane + 3 mm glass Door frame Timber 40 2 1632.85 0 Door pane Timber 40 2 1632.85 0

4. Results and Discussion The results in this section present data from Hudhayfah and Al Waﬁ mosques’ simulations. Both mosques’ simulation results are split into winter and summer results. The winter results and summer results presented are for the winter design day in Muscat, day 20, and the summer design day in Muscat, day 179, respectively. The presented results compare between the external dry bulb temperature (DBT), internal DBT, and loads breakdown of the different zones in each mosque.

4.1. Hudhayfah Mosque Winter Simulation Results Hudhayfah mosque Zone 20s DBT is higher than Zone 10s DBT throughout day 20. Figure 10 shows the external DBT during the coldest day of the year, day 20, along with the DBT inside the mosque. Both zones maintain a higher DBT than external temperature throughout the day. Zone 20s temperature is consistently higher than Zone 1 throughout the day by at least 2 ◦C at 07:00 and reaches to a difference of up to 6 ◦C at 14:00. It is also evident that Zone 20s DBT ﬂuctuates throughout the day similar to external DBT. Zone 2 DBT increases from 26 ◦C at 07:00 to 30 ◦C at 14:00, while Zone 1 stays within one degree Celsius from 23 ◦C. Zone 20s higher DBT could be attributed to higher solar gain. Figure 11 shows the breakdown of the most inﬂuential loads for Zones 1 and 2. The main contributing factor for heat gain and heat loss for both zones are solar gain and external opaque conduction, respectively. Solar gain starts to increase by 07:00, reaches its peak at 11:00, and gradually decreases to zero by sunset. Most of the heat gain during this period is lost via external opaque conduction. Zone 2 is affected more by solar gain, hence the increase in DBT through the day, while Zone 1 keeps a steady DBT through day and night at 23 degrees Celsius. Zone 2 has a higher glazing ratio in external walls of 59% compared to 27.5% for Zone 1. Most of Zone 2 windows are in the eastern wall, which is exposed to direct sunlight, hence a higher solar gain. Buildings 2021, 11, x FOR PEER REVIEW 10 of 20

32 30 28 26 24 22 20 Buildings 2021 11 18 Buildings 2021, 11, x FOR, , PEER 314Temperature (°C) REVIEW 10 of 20 10 of 20 16 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (Hour) 32 30 External Dry Bulb Temperature Zone 1 DBT Zone 2 DBT 28 26 Figure24 10. External dry bulb temperature and internal dry bulb temperatures in Hudhayfah Mosque by the hour during day 2022 (Winter). 20 18 Zone 2′s higher DBT could be attributed to higher solar gain. Figure 11 shows the Temperature (°C) 16 breakdown of the most influential loads for Zones 1 and 2. The main contributing factor 14 for heat gain and heat loss for both zones are solar gain and external opaque conduction, 1 2 3 4respectively. 5 6 7 8Solar 9 gain 10 starts 11 12 to 13increase 14 15 by 16 07:00, 17 reaches 18 19 its 20 peak 21 at 22 11:00, 23 24 and gradually decreases to zero by sunset.Time Most (Hour) of the heat gain during this period is lost via external opaque conduction. Zone 2 is affected more by solar gain, hence the increase in DBT External throughDry Bulb Temperaturethe day, while Zone 1 keepsZone a steady1 DBT DBT throughZone day 2and DBT night at 23 degrees Celsius. Zone 2 has a higher glazing ratio in external walls of 59% compared to 27.5% for Figure 10.Figure External 10. External dry bulb dry bulbtemperatureZone temperature 1. Most and and internalof internal Zone dry2 dry windows bulb temperatures temperatures are in the in eastern Hudhayfahin Hudhayfah wall, Mosque which Mosque by is the exposed by hour the during hour to direct during sun ‐ day 20 (Winter).day 20 (Winter). light, hence a higher solar gain.

20,000 Zone 2′s higher DBT could be attributed30,000 to higher solar gain. Figure 11 shows the 15,000 breakdown of the most influential loads20,000 for Zones 1 and 2. The main contributing factor 10,000 for heat gain and heat loss for both zones are solar gain and external opaque conduction, 5,000 10,000 respectively. Solar gain starts to increase by 07:00, reaches its peak at 11:00, and gradually 0 0

Load (W) -5,000 decreases to zero by sunset. Most ofLoad (W) the heat gain during this period is lost via external -10,000 -10,000 opaque conduction. Zone 2 is affected more by solar gain, hence the increase in DBT -15,000 -20,000 1 3 5through 7 9 11131517192123 the day, while Zone 1 keeps a steady1357911131517192123 DBT through day and night at 23 degrees Celsius.Time Zone(Hour) 2 has a higher glazing ratio in external wallsTime of(Hour) 59% compared to 27.5% for Zone 1. Most of Zone 2 windows are in the eastern wall, which is exposed to direct sun‐ Zone 1 Solarlight, Gain hence a higher solar gain. Zone 2 Solar Gain Zone 1 Inf/Vent Gain Zone 2 Inf/Vent Gain Zone 1 Building Heat Transfer Zone 2 Building Heat Transfer 20,000 Zone 1 External Opaque Conduction 30,000 Zone 2 External Opaque Conduction Zone 1 External Glazing Conduction 15,000 20,000 Zone 2 External Glazing Conduction 10,000 5,000 10,000 0 (a) 0 (b)

Load (W) -5,000 Load (W) Figure 11. (a) Loads breakdown in Hudhayfah mosque (Zone 1) during day 20 (winter); (b) loads breakdown in Hudhay‐ -10,000Figure 11. (a) Loads breakdown in Hudhayfah mosque (Zone 1) during-10,000 day 20 (winter); (b) loads breakdown in Hudhayfah fah mosque (Zone 2) during day 20 (winter). -15,000mosque (Zone 2) during day 20 (winter). -20,000 1 3 5 7 9 11131517192123 1357911131517192123 Time 4.2.(Hour)4.2. Hudhayfah Hudhayfah Mosque Mosque Summer Summer Simulation Simulation Results Results Time (Hour) UnlikeUnlike summer, summer, during during winter winter both both zones zones of Hudhayfah of Hudhayfah mosque mosque have have a very a very similar similar DBTDBT throughout throughout day day 179. 179. Figure Figure 12 a12a shows shows the the external external DBT DBT during during the summer the summer design design Zone 1 Solar Gain Zone 2 Solar Gain day,day, day day 179, 179, compared compared to the to internal the internal DBT inside DBT theinside mosque the mosque and the cooling and the load cooling required, load re‐ Zone 1 Inf/Vent Gain Zone 2 Inf/Vent Gain respectively.quired, respectively. The external The DBT external reaches DBT 44.8 reaches C. Both 44.8 zones C. reachBoth zones the setpoint reach temperaturethe setpoint tem‐ Zone 1 Building Heat Transfer Zone 2 Building Heat Transfer duringperature the during two periods the two as per periods the schedule as per (3the am schedule to 5 am, and(3 am 12 to pm 5 toam, 9 pm). and The12 pm cooling to 9 pm). Zone 1 External Opaque Conduction Zone 2 External Opaque Conduction Zone 1 External Glazingsystem Conduction start and ends at the times mentioned, which means that the system turns off every day at 5 a.m. and 9 p.m. Zone 2 External Glazing Conduction

(a) (b) Figure 11. (a) Loads breakdown in Hudhayfah mosque (Zone 1) during day 20 (winter); (b) loads breakdown in Hudhay‐ fah mosque (Zone 2) during day 20 (winter).

4.2. Hudhayfah Mosque Summer Simulation Results Unlike summer, during winter both zones of Hudhayfah mosque have a very similar DBT throughout day 179. Figure 12a shows the external DBT during the summer design day, day 179, compared to the internal DBT inside the mosque and the cooling load re‐ quired, respectively. The external DBT reaches 44.8 C. Both zones reach the setpoint tem‐ perature during the two periods as per the schedule (3 am to 5 am, and 12 pm to 9 pm). Buildings 2021, 11, x FOR PEER REVIEW 11 of 20

Buildings 2021, 11, 314 11 of 20 The cooling system start and ends at the times mentioned, which means that the system turns off every day at 5 am and 9 pm.

120,000 46 100,000 40 80,000 34 60,000 28 Load (W) Temperature (°C) 40,000 22 1357911131517192123 20,000 Time (Hour) 0 1 3 5 7 9 11 13 15 17 19 21 23 External Dry Bulb Temperature Time (Hour) Zone 1 DBT Zone 1 CL Zone 2 CL Zone 2 DBT

(a) (b)

FigureFigure 12. 12.(a) ( Externala) External dry dry bulb bulb temperature temperature versus versus internal internal dry dry bulb bulb temperature temperature in summer in summer in Hudhayfah in Hudhayfah mosque mosque during dur‐ daying 179; day (b 179;) cooling (b) cooling load (CL) load during (CL) during summer summer in Hudhayfah in Hudhayfah mosque mosque by the hourby the during hour during day 179. day 179.

ZoneZone 2 peak2 peak cooling cooling load load is is about about 25,864 25,864 Watts Watts while while Zone Zone 1 peak1 peak cooling cooling load load is is 102,406102,406 Watts Watts although although both both spaces spaces have have the the same same thermostat thermostat setpoint setpoint of 23of 23◦C °C as as shown shown inin Figure Figure 12 b.12b. Zone Zone 20s 2 smaller′s smaller area, area, 174 174 m2, m compared2, compared to Zone to Zone 10s area 1′s area of 906 of m 9062, could m2, could be onebe of one the of factors the factors for the for high the difference high difference in cooling in cooling load demand load demand between between the two the zones two [ zones10]. From[10]. 5:00 From to 5:00 12:00 to the12:00 air the conditioning air conditioning system system does does not operate,not operate, and and the the external external DBT DBT ◦ increasesincreases by by 10 10 degrees degrees during during thisthis period from from 33 33 to to 43 43 °C.C. Hence, Hence, the the internal internal DBT DBT man‐ ◦ ◦ managesages to to increase increase from from 23 23 °CC at at 5:00 5:00 to 35.6 °CC atat 12:00 12:00 before before the the air air conditioning conditioning system system startsstarts again again for for the the second second period. period. FigureFigure 13 13shows shows the the loads loads breakdown breakdown for for Zones Zones 1 and1 and 2 during 2 during summer. summer. Sensible Sensible loadsloads shown shown are are for for the the active active cooling cooling load load by by the the air air conditioning conditioning system system during during the the two two occupancyoccupancy periods. periods. External External opaque opaque conduction conduction contributes contributes to to heat heat gain gain as as a countera counter to to thethe sensible sensible load load during during the the occupancy occupancy periods. periods. Between Between 5:00 5:00 and and 12:00 12:00 when when the the mosque mosque is notis not occupied, occupied, solar solar gain gain is theis the main main factor factor to to heat heat gain. gain. In In contrast contrast to to the the winter, winter, Zone Zone 1 1 hashas more more solar solar gain gain than than Zone Zone 2 when2 when it isit freeis free running. running. This This could could be be attributed attributed to to the the Buildings 2021, 11, x FOR PEER REVIEWdifferent solar orientation and the longer periods of exposure to solar irradiance12 inof summer20 different solar orientation and the longer periods of exposure to solar irradiance in sum‐ comparedmer compared to winter. to winter.

15,000 30,000 10,000 10,000 5,000 -10,000 0 -30,000 -5,000 -50,000 -10,000

Load (W) Load (W) -15,000 -70,000 -20,000 -90,000 -25,000 -110,000 -30,000 1357911131517192123 1357911131517192123 Time (Hour) Time (Hour)

Zone 1 Sensible Load Zone 2 Sensible Load Zone 1 Solar Gain Zone 2 Solar Gain Zone 1 Inf/Vent Gain Zone 2 Inf/Vent Gain Zone 1 Building Heat Transfer Zone 2 Building Heat Transfer Zone 1 External Opaque Conduction Zone 2 External Opaque Conduction Zone 1 External Glazing Conduction Zone 2 External Glazing Conduction

(a) (b)

FigureFigure 13. ( a13.) Loads (a) Loads breakdown breakdown in in Hudhayfah Hudhayfah mosque mosque (Zone 1) 1) during during day day 179 179 (summer); (summer); (b) loads (b) loads breakdown breakdown in in Hudhayfah mosque (Zone 2) during day 179 (summer). Hudhayfah mosque (Zone 2) during day 179 (summer). 4.3. Al Wafi Mosque Winter Simulation Results Unlike the Hudhayfah mosque, Zone 1 and 2 of Al Wafi mosque had similar DBT throughout the winter design day. Figure 14 shows the external DBT during the coldest day of the year, day 20, along with the internal DBT. The simulation is free running during the winter. Zone 1 maintains a steady DBT throughout the day closer to 23 °C, while Zone 2 fluctuates between 22 and 25 °C. Zone 2 has the entire eastern wall as an aluminium partition wall with windows throughout the whole top part of the wall. Zone 3 is an ex‐ posed area, and that is why its DBT is very similar to external DBT. See the layout of Al Wafi mosque in Figure 7.

17 Temperature (°C)

14 123456789101112131415161718192021222324 Time (Hour)

External Dry Bulb Temperature Al Wafi Zone 1 DBT Al Wafi Zone 2 DBT Zone 3 DBT

Figure 14. External DBT vs. Al Wafi DBT in winter by the hour during day 20.

Loads breakdown are shown for Zones 1 and 2 in Figure 15. Both zones gain heat through external opaque conduction during night‐time although external DBT is lower than internal DBT (reaches a difference of up to 8 degrees Celsius). The buildings are be‐ lieved to gain heat via the heat absorbed into the thermal mass. Al Wafi mosque’s clay walls have relatively similar heat capacity and density as Hudhayfah’s concrete walls. Al Buildings 2021, 11, x FOR PEER REVIEW 12 of 20

15,000 30,000 10,000 10,000 5,000 -10,000 0 -30,000 -5,000 -50,000 -10,000

Load (W) Load (W) -15,000 -70,000 -20,000 -90,000 -25,000 -110,000 -30,000 1357911131517192123 1357911131517192123 Time (Hour) Time (Hour)

Buildings 2021, 11, 314 (a) (b) 12 of 20 Figure 13. (a) Loads breakdown in Hudhayfah mosque (Zone 1) during day 179 (summer); (b) loads breakdown in Hudhayfah mosque (Zone 2) during day 179 (summer).

4.3.4.3. AlAl WafiWafi MosqueMosque Winter Simulation Results UnlikeUnlike the Hudhayfah mosque, Zone Zone 1 1 and and 2 2 of of Al Al Wafi Wafi mosque mosque had had similar similar DBT DBT throughoutthroughout thethe winter design day. Figure 14 showsshows the the external external DBT DBT during during the the coldest coldest dayday ofof thethe year, day 20, along with the the internal internal DBT. DBT. The The simulation simulation is is free free running running during during ◦ thethe winter.winter. ZoneZone 11 maintains a steady DBT throughout throughout the the day day closer closer to to 23 23 °C,C, while while Zone Zone ◦ 22 fluctuatesfluctuates betweenbetween 22 and 25 °C.C. Zone 2 2 has has the the entire entire eastern eastern wall wall as as an an aluminium aluminium partitionpartition wall with windows windows throughout throughout the the whole whole top top part part of the of the wall. wall. Zone Zone 3 is an 3 is ex an‐ exposedposed area, area, and and that that is iswhy why its its DBT DBT is is very very similar similar to to external external DBT. DBT. See See the the layout layout of of Al Al WafiWafi mosque mosque in in Figure Figure7 7..

17 Temperature (°C)

14 123456789101112131415161718192021222324 Time (Hour)

External Dry Bulb Temperature Al Wafi Zone 1 DBT Al Wafi Zone 2 DBT Zone 3 DBT

FigureFigure 14. 14. ExternalExternal DBTDBT vs. Al Wafi Waﬁ DBT in winter by the hour during during day day 20. 20.

LoadsLoads breakdownbreakdown are shown for Zones 1 1 and and 2 2 in in Figure Figure 15.15. Both Both zones zones gain gain heat heat throughthrough externalexternal opaque conduction during during night night-time‐time although although external external DBT DBT is is lower lower thanthan internalinternal DBT DBT (reaches (reaches a a difference difference of of up up to to8 degrees 8 degrees Celsius). Celsius). The Thebuildings buildings are be are‐ Buildings 2021, 11, x FOR PEER REVIEW 13 of 20 believedlieved to to gain gain heat heat via via the the heat heat absorbed absorbed into into the the thermal thermal mass. mass. Al Al Wafi Wafi mosque’s mosque’s clay clay wallswalls havehave relativelyrelatively similar heat capacity and density density as as Hudhayfah’s Hudhayfah’s concrete concrete walls. walls. Al Al Wafi mosque, though, features clay walls (up to 1.2 metres thick) almost three times the Wafi mosque, though, features clay walls (up to 1.2 metres thick) almost three times the thicknessthickness of Hudhayfah of Hudhayfah concrete concrete walls walls (0.375 (0.375 metres metres thick). thick). Al Al Wafi Wafi external external walls walls feature feature significantlysignificantly higher higher time time constant constant as as per per Tables Tables3 and 3 and4. Consequently,4. Consequently, it it is is reflected reflected into into Al Wafi’sAl clay Wafi’s wall clay to wall have to a have continuous a continuous high high external external opaque opaque conduction conduction loadload through throughout‐ winterout nights winter and nights mornings. and mornings.

1000 4000 500 2000 0 0 Load (W) Load (W) -500 -2000 -1000 -4000 1 3 5 7 9 11 13 15 17 19 21 23 1357911131517192123 Time (Hour) Time (Hour)

Zone 1 Solar Gain Zone 2 Solar Gain Zone 1 Inf/Vent Gain Zone 2 Inf/Vent Gain Zone 1 Building Heat Transfer Zone 2 Building Heat Transfer Zone 1 External Opaque Conduction Zone 2 External Opaque Conduction Zone 1 External Glazing Conduction Zone 2 External Glazing Conduction

(a) (b)

Figure 15.Figure(a) Loads 15. (a) breakdown Loads breakdown in Al Waﬁ in Al mosque Wafi mosque (Zone 1)(Zone during 1) during day 20 day (winter); 20 (winter); (b) loads (b) loads breakdown breakdown in Al in Waﬁ Al Wafi mosque mosque (Zone 2) during day 20 (winter). (Zone 2) during day 20 (winter). Solar gain reaches a peak of 735 Watts for Zone 1 at 13:00, while the peak of Zone 2 is 3502 Watts, which happens at 10:00. Zone 2 has a glazing ratio of 10% compared to Zone 1′s glazing ratio of 4.2%. The higher solar gain for Zone 2 could be attributed to the orien‐ tation of Zone 2′s glazed wall to the east, which is exposed directly to sunlight between 9:00 and 12:00.

4.4. Al Wafi Mosque Summer Simulation Results Figure 16 shows Al Wafi mosque’s external DBT during the hottest day of the year, day 179, compared to the cooling load required. The external DBT reaches 44.8 °C. The thermostat set point is set at 23 °C, and that is why Zones 1 and 2 reach this temperature during the two air‐conditioning periods as per the schedule (3 am to 5 am, and 12 pm to 9 pm). Unlike Hudhayfah mosque’s summer case, Al Wafi mosques’ two zones react dif‐ ferently during the unoccupied period from 5:00 to 12:00. Al Wafi Zone 1 increases its DBT by 10 °C while Zone 2 increases by 16 °C from the thermostat setpoint temperature (23 °C). Figure 17 shows the loads breakdown for Al Wafi mosque during summer for Zone 1 and Zone 2, respectively. As the space is air conditioned, the higher difference between internal and external DBT means an increasing external conduction gain through the building envelope. Buildings 2021, 11, 314 13 of 20

Solar gain reaches a peak of 735 Watts for Zone 1 at 13:00, while the peak of Zone 2 is 3502 Watts, which happens at 10:00. Zone 2 has a glazing ratio of 10% compared to Zone 10s glazing ratio of 4.2%. The higher solar gain for Zone 2 could be attributed to the orientation of Zone 20s glazed wall to the east, which is exposed directly to sunlight between 9:00 and 12:00.

4.4. Al Wafi Mosque Summer Simulation Results Figure 16 shows Al Wafi mosque’s external DBT during the hottest day of the year, day 179, compared to the cooling load required. The external DBT reaches 44.8 ◦C. The thermostat set point is set at 23 ◦C, and that is why Zones 1 and 2 reach this temperature during the two air-conditioning periods as per the schedule (3 am to 5 am, and 12 pm to 9 pm). Unlike Hudhayfah mosque’s summer case, Al Wafi mosques’ two zones react differently during the unoccupied period from 5:00 to 12:00. Al Wafi Zone 1 increases its DBT by 10 ◦C while Zone 2 increases by 16 ◦C from the thermostat setpoint temperature (23 ◦C). Figure 17 shows the loads breakdown for Al Wafi mosque during summer for Zone 1 and Zone 2, respectively. As the space is air conditioned, the higher difference between Buildings 2021, 11, x FOR PEER REVIEW 14 of 20 internal and external DBT means an increasing external conduction gain through the building envelope.

50 45,000 46 40,000 42 35,000 38 30,000 34 25,000 30 20,000 Load (W) Temperature (°C) 26 15,000 22 10,000 1357911131517192123 5,000 Time (Hour) 0 1 3 5 7 9 11 13 15 17 19 21 23 External Dry Bulb Temperature Time (Hour) Al Wafi Zone 1 DBT Al Wafi Zone 2 DBT Al Wafi Zone 1 CL Al Wafi Zone 2 CL

(a) (b)

FigureFigure 16. 16.(a) ( Externala) External DBT DBT vs. vs. DBT DBT in in summer summer in Alin Al Waﬁ Wafi Mosque Mosque during during day day 179; 179; (b) ( externalb) external DBT DBT vs. vs. CL CL in summerin summer in in AlAl Waﬁ Wafi Mosque Mosque during during day day 179. 179.

It was noticed that Zone 2 is more affected by solar gain than Zone 1. This is due to the 11,000 incidence of sunlight that directly affects the east and west walls during the summer. Zone 8,000 20s east wall is mostly exposed to sunlight6,000 between 7:00 and 12:00 and has a glazing ratio 0 -2,000 of 13.65%. Zone 1 s west wall is exposed to1,000 sunlight between 12:00 and 19:00, and it has a glazing ratio of 3.86% in the west wall. Hence,-4,000 Zone 1 is less affect by solar gain than Zone -12,000 2. Building heat transfer also impacts Zone-9,000 2 more than Zone due to the building envelope Load (W) -22,000 of both zones. The walls of the mosque areLoad (W) all thick clay walls that varies between 500 and 1200 mm, except for the east wall of Zone 2-14,000 which is 15-milimetre aluminium partition wall. -32,000 This wall was added during the 2000s to-19,000 close Zone 2, which was previously a Riwaq (an -42,000 arcade). Zone 2 east wall would allow more-24,000 heat to be transferred from than other walls 1 3 5 7due 9 to11 its 13 higher 15 17 19 U-value 21 23 of 7.27 W/m2·K compared1 3 to 5 0.7 7 W/m 9 111315171921232·K U-value for clay wall. Time (Hour) Time (Hour)

Zone 1 Sensible Load Zone 2 Sensible Load Zone 1 Inf/Vent Gain Zone 2 Solar Gain Zone 1 Building Heat Transfer Zone 2 Inf/Vent Gain Zone 1 External Opaque Conduction Zone 2 Building Heat Transfer Zone 1 Solar Gain Zone 2 External Opaque Conduction

(a) (b) Figure 17. (a) Loads breakdown in Al Wafi mosque (Zone 1) during day 179 (summer); (b) loads breakdown in Al Wafi mosque (Zone 2) during day 179 (summer).

It was noticed that Zone 2 is more affected by solar gain than Zone 1. This is due to the incidence of sunlight that directly affects the east and west walls during the summer. Zone 2′s east wall is mostly exposed to sunlight between 7:00 and 12:00 and has a glazing ratio of 13.65%. Zone 1′s west wall is exposed to sunlight between 12:00 and 19:00, and it has a glazing ratio of 3.86% in the west wall. Hence, Zone 1 is less affect by solar gain than Zone 2. Building heat transfer also impacts Zone 2 more than Zone due to the building envelope of both zones. The walls of the mosque are all thick clay walls that varies be‐ tween 500 and 1200 mm, except for the east wall of Zone 2 which is 15‐milimetre alumin‐ ium partition wall. This wall was added during the 2000s to close Zone 2, which was pre‐ viously a Riwaq (an arcade). Zone 2 east wall would allow more heat to be transferred from than other walls due to its higher U‐value of 7.27 W/m2.K compared to 0.7 W/m2.K U‐value for clay wall. Buildings 2021, 11, x FOR PEER REVIEW 14 of 20

(a) (b) Buildings 2021, 11, 314 14 of 20 Figure 16. (a) External DBT vs. DBT in summer in Al Wafi Mosque during day 179; (b) external DBT vs. CL in summer in Al Wafi Mosque during day 179.

11,000 8,000 6,000

-2,000 1,000 -4,000 -12,000 -9,000 Load (W) -22,000 Load (W) -14,000 -32,000 -19,000 -42,000 -24,000 1 3 5 7 9 11 13 15 17 19 21 23 1 3 5 7 9 11131517192123 Time (Hour) Time (Hour)

Buildings 2021, 11, x FORZone PEER 1 SensibleREVIEW Load Zone 2 Sensible Load 15 of 20

Zone 1 Inf/Vent Gain Zone 2 Solar Gain Zone 1 Building Heat Transfer Zone 2 Inf/Vent Gain Zone 1 External4.5. Opaque Comparison Conduction between Hudhayfah and Al Wafi MosquesZone 2 Building Heat Transfer Zone 1 Solar Gain Figure 18a shows the DBT of both HudhayfahZone 2 Externaland Al Opaque Wafi Conduction mosques’ Zone 1 com‐

pared to the external DBT in winter. Both Mosques appear to maintain their internal DBT (a) (b) similarly in a free running building setting. FigureFigure 17. 17.(a) ( Loadsa) Loads breakdown breakdown in Figurein Al Al Wafi Wafi 18b mosque mosque shows (Zone (Zone the 1) duringsame,1) during daybut day 179in 179 summer. (summer); (summer); Hudhayfah (b )(b loads) loads breakdown breakdown appears in toin Al Albe Wafi Wafiaffected mosquemosque (Zone (Zone 2) during2) during day day 179slightly 179 (summer). (summer). more by the rise of external DBT, which can be attributed to the different in U‐ value of the two mosques’ building envelope. Hudhayfah mosque’s walls, which consist 4.5.of Comparisona 350It was mm noticed thick between concrete that Hudhayfah Zone brick 2 is and wall more Al with Wafi affected 50 Mosques mm by thick solar polyurethane gain than Zone thermal 1. This insulation is due to board,theFigure incidence have 18a a shows oflower sunlight the U‐value DBT that of ofdirectly both 0.4 W/m Hudhayfah affects2.K compared the and east Al and Wafito awest U mosques’‐value walls of during Zone 0.7 W/m 1 the compared2 .Ksummer. for Al toWafiZone the external mosque’s2′s east DBT wall clay in is winter. walls.mostly Al Both exposed Wafi Mosques mosque’s to sunlight appear Zone between to 1 maintain external 7:00 their walls and internal 12:00 have anda DBTglazing has similarly a glazingratio of injustratio a free 4.2% of running 13.65%. compared building Zone to 1 a′s setting.27.5% west wallglazing is exposed ratio for to Hudhayfah sunlight between Zone 1 ′12:00s external and 19:00,walls. and it has a glazing ratio of 3.86% in the west wall. Hence, Zone 1 is less affect by solar gain than Zone 2. Building heat transfer also impacts Zone 2 more than Zone due to the building 24 envelope of both zones. The walls of47 the mosque are all thick clay walls that varies be‐ 23 tween 500 and 1200 mm, except for the east wall of Zone 2 which is 15‐milimetre alumin‐ 22 ium partition wall. This wall was added42 during the 2000s to close Zone 2, which was pre‐ 21 viously a Riwaq (an arcade). Zone 2 east wall would allow more heat to be transferred 20 37 19 from than other walls due to its higher U‐value of 7.27 W/m2.K compared to 0.7 W/m2.K 18 U‐value for clay wall. 32 17 Temperature (°C) Temperature (°C) 16 27 15 14 22 1 3 5 7 9 11 13 15 17 19 21 23 1357911131517192123 Time (Hour) Time (Hour)

External Dry Bulb Temperature External Dry Bulb Temperature Hudhayfah Zone 1 DBT Hudhayfah Zone 1 DBT Al Wafi Zone 1 DBT Al Wafi Zone 1 DBT

(a) (b)

FigureFigure 18. 18.(a )( Comparisona) Comparison between between Hudhayfah Hudhayfah and and Al WaﬁAl Wafi mosque’s mosque’s Zone Zone 1 dry 1 bulbdry bulb temperatures temperatures during during Day 20Day (Winter); 20 (Win‐ (b)ter); Comparison (b) Comparison between between Hudhayfah Hudhayfah and Al and Waﬁ Al mosque’s Wafi mosque’s Zone 1 Zone dry bulb 1 dry temperatures bulb temperatures during during Day 179 Day (Summer). 179 (Summer).

FigureFigures 18b 19 shows and the20 show same, the but cooling in summer. load Hudhayfah in each of appearsthe mosques to be affectedis different. slightly Total morecooling by the load rise is ofhigher external for Hudhayfah DBT, which mosque’s can be attributed Zone 1 given to the its different larger area in U-value (See Table of 1 thefor two areas mosques’ of each zone). building On envelope.the other hand, Hudhayfah the cooling mosque’s load per walls, area which and the consist cooling of load a 350per mm volume thick concreteare the lowest brick wallfor Hudhayfah with 50 mm mosque’s thick polyurethane Zone 1. It is thermal also observed insulation that board, cooling load per area and per volume are substantially higher for Zone 2 of both mosques. Buildings 2021, 11, 314 15 of 20

have a lower U-value of 0.4 W/m2·K compared to a U-value of 0.7 W/m2·K for Al Waﬁ mosque’s clay walls. Al Waﬁ mosque’s Zone 1 external walls have a glazing ratio of just 4.2% compared to a 27.5% glazing ratio for Hudhayfah Zone 10s external walls. Figures 19 and 20 show the cooling load in each of the mosques is different. Total cooling load is higher for Hudhayfah mosque’s Zone 1 given its larger area (See Table1 for areas of each zone). On the other hand, the cooling load per area and the cooling load per Buildings 2021, 11, x FOR PEER REVIEW 16 of 20 Buildings 2021, 11, x FOR PEER REVIEWvolume are the lowest for Hudhayfah mosque’s Zone 1. It is also observed that cooling16 of 20 load per area and per volume are substantially higher for Zone 2 of both mosques.

160 100,000 160 100,000 140

140) 2

) 120 80,000 2 80,000 120 100 60,000 100 60,000 80 80 Load (W) 40,000 60 Load (W) 40,000 60 40 20,000 40Load per area (W/m 20,000 Load per area (W/m 20 20 0 0 0 1 3 5 7 9 11 13 15 17 19 21 23 0 1357911131517192123 1 3 5 7 9 11 13 15 17 19 21 23 1357911131517192123 Time (Hour) Time (Hour) Time (Hour) Time (Hour)

Hudhayfah Zone 1 Hudhayfah Zone 2 Hudhayfah Zone 1 Hudhayfah Zone 2 Hudhayfah Zone 1 Hudhayfah Zone 2 Hudhayfah Zone 1 Hudhayfah Zone 2 Al Wafi Zone 1 Al Wafi Zone 2 Al Wafi Zone 1 Al Wafi Zone 2 Al Wafi Zone 1 Al Wafi Zone 2 Al Wafi Zone 1 Al Wafi Zone 2

(a) (b) (a) (b) FigureFigure 19. 19.(a) ( Comparisona) Comparison between between Hudhayfah Hudhayfah and and Al Al Waﬁ Wafi mosque’s mosque’s total total cooling cooling loads loads across across Zones Zones 1 and 1 and 2 for 2 for both both Figure 19. (a) Comparison between Hudhayfah and Al Wafi mosque’s total cooling loads across Zones 1 and 2 for both mosquesmosques during during day day 179 179 (Summer); (Summer); (b )(b comparison) comparison between between Hudhayfah Hudhayfah and and Al Al Waﬁ Wafi mosque’s mosque’s cooling cooling loads loads per per area area mosquesacross Zonesduring 1 day and 1792 for (Summer); both mosques (b) comparison during day between179 (Summer). Hudhayfah and Al Wafi mosque’s cooling loads per area across Zones 1 and 2 for both mosques during day 179 (Summer).

45 )

453

) 40 3 40 35 35 30 30 25 25 20 20 15 15 10 10 5 5Load per volume (W/m

Load per volume (W/m 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (Hour) Time (Hour)

Hudhayfah Zone 1 Hudhayfah Zone 2 Al Wafi Zone 1 Al Wafi Zone 2 Hudhayfah Zone 1 Hudhayfah Zone 2 Al Wafi Zone 1 Al Wafi Zone 2

Figure 20. Comparison between Hudhayfah and Al Wafi mosques’ cooling loads per volume across Zones 1 and 2 for Figureboth 20. mosques Comparison during betweenbetween day 179 Hudhayfah (Summer).Hudhayfah and and Al Al Waﬁ Wafi mosques’ mosques’ cooling cooling loads loads per per volume volume across across Zones Zones 1 and 1 2and for 2 both for bothmosques mosques during during day 179 day (Summer). 179 (Summer). It could also prove that traditional mosques achieve better performance for passive It could also prove that traditional mosques achieve better performance for passive cooling,It could while also contemporary prove that traditional mosques mosques achieve better achieve performance better performance for active for cooling. passive It is cooling, while contemporary mosques achieve better performance for active cooling. It is cooling,evident while that contemporaryAl Wafi mosque mosques requires achieve the most better cooling performance load per for area active and cooling.per volume It is as evident that Al Wafi mosque requires the most cooling load per area and per volume as evidentper Figures that Al 19b Waﬁ and mosque 20, respectively. requires the most cooling load per area and per volume as per Figures 19b19b and 20,20, respectively. 4.6. Validation of Simulated Model 4.6. Validation of Simulated Model The simulated data was validated using measured energy consumption from elec‐ The simulated data was validated using measured energy consumption from elec‐ tricity bills of both mosques. Cooling load from the simulated data was compared to the tricity bills of both mosques. Cooling load from the simulated data was compared to the air conditioning energy consumption. According to ASHRAE Guideline 14–2014, the ac‐ air conditioning energy consumption. According to ASHRAE Guideline 14–2014, the ac‐ curacy of a simulation can be checked using normalized mean bias error (NMBE) and curacy of a simulation can be checked using normalized mean bias error (NMBE) and coefficient of variance of the root mean squared error (CV RMSE) [34,35]. coefficient of variance of the root mean squared error (CV RMSE) [34,35]. 1 ∑m s NMBE 1 ∑ m s 100 % NMBE m n p 100 % m n p Buildings 2021, 11, 314 16 of 20

4.6. Validation of Simulated Model The simulated data was validated using measured energy consumption from electricity bills of both mosques. Cooling load from the simulated data was compared to the air conditioning energy consumption. According to ASHRAE Guideline 14–2014, the accuracy of a simulation can be checked using normalized mean bias error (NMBE) and coefﬁcient of variance of the root mean squared error (CV RMSE) [34,35].

1 ∑n (m − s ) NMBE = · i=1 i i × 100 (%) m n − p

s 2 1 ∑n (m − s ) CV (RMSE) = · i=1 i i × 100 (%) m n − p

mi = measured data si = simulated data n = number of data points p = number of adjustable model parameters m = mean of measured data According to ASHRAE Guideline 14–2014, the acceptable range of tolerances are 5% and 15% for NMBE and CV RMSE, respectively, which both buildings meet as shown in Table5[34].

Table 5. NMBE and CV RMSE calibration values for Hudhayfah and Al Waﬁ mosques.

Mosque NMBE CV RMSE Hudhayfah Mosque 2% 14% Al Waﬁ Mosque 1% 15%

4.7. Application of Different Improvements to the Buildings and Its Effect on Cooling Load There are many enhancements that can be done to improve a building’s thermal performance. In this section, several improvements were applied to both Hudhayfah Mosque and Al Wafi mosque. Zones 1 of both mosques are subsequently compared with the seven different improved cases. Zone 1 was chosen for the comparisons as it is the main prayer hall where prayer is performed, whereas Zone 2 in both mosques is used mainly as a foyer to Zone 1. Fenestration, building envelope insulation, building material, and thermostat set point are believed to be areas for potential improvement in buildings in hot arid regions [13,36]. Fenestration can be argued as the weakest element in a building. Controlling the window- to-wall ration (or glazing ratio) is key to achieve higher building efficiency. A study conducted in mosques in Saudi Arabia concluded that the optimal value for glazing ratio is around 15% overall [14]. To see the effect of the glazing ratio on both Hudhayfah and Al Wafi mosques, the value will be halved and doubled as can be seen in 1st and 2nd cases, respectively, of Tables6 and7. It is also recommended to decrease the U-value of the building envelope to limit thermal transmittance into the building [10]. The 3rd and 4th cases represent cases of halving the U-value of the roof and walls, respectively, in Tables6 and7. The 5th case is an experiment to exchange between the concrete and mud wall and vice-versa for Hudhayfah and Al Wafi mosques. Increasing the thermostat set point also yields considerable savings in cooling loads. As per a study conducted on mosques in Kuwait, an electrical energy saving of 10% was achieved by increasing the thermostat temperature by 1 ◦C[15]. In another study conducted on government buildings of Oman, it concluded that increasing the set point by 3 ◦C yielded annual energy savings of 13.23% [16]. The thermostat set point is increased by 1 and 2 ◦C in the 6th and 7th cases, respectively. Buildings 2021, 11, 314 17 of 20

Table 6. Application of improvement cases into Hudhayfah Mosque simulation model.

Description of the Alteration of Each Case in Change in Cooling Parameters Comparison to the Base Case Load Base case - 1st case Half the glazing ratio +2% 2nd case Double the glazing ratio +9% Roof’s U value reduced from 0.816 W/m2·C to 3rd case −7% 0.413 W/m2·C External wall’s U value reduced from 0.403 W/m2·C to 4th case +2% 0.201 W/m2·C Building envelope material changed from Concrete to 5th case +7% Mud wall 6th case Thermostat setpoint increase by 1 ◦C −2% 7th case Thermostat setpoint increase by 2 ◦C −6%

Table 7. Application of improvement cases into Al Waﬁ Mosque simulation model.

Description of the Alteration of Each Case in Change in Cooling Parameters Comparison to the Base Case Load Base case - 1st case Half the glazing ratio −1% 2nd case Double the glazing ratio +3% Roof’s U value reduced from 1.25 W/m2·C to 3rd case −4% 0.62 W/m2·C External wall’s U value reduced from 0.722 W/m2·C to 4th case 0% 0.361 W/m2·C Building envelope material changed from mud wall to 5th case +13% concrete 6th case Thermostat setpoint increase by 1 ◦C −5% 7th case Thermostat setpoint increase by 2 ◦C −9%

As per Table6, it is evident that the insulating the roof and increasing the setpoint by 2 ◦C yielded cooling load savings of −7% and −6% respectively. When changing the building walls and roof from concrete to mud wall, cooling load increased by 7%. As per Table7, it is evident that increasing the setpoint by 1 and 2 ◦C yielded cooling load savings of −5% and −9% respectively. When changing the building walls and roof from clay wall to concrete, cooling load demand increased by 13%.

5. Research Limitations • All charts indicate spot results at 60 min intervals. Values in between the 60 min intervals are not calculated. • This research focused more on comparing the thermal performance of the buildings rather than the thermal comfort of occupants and indoor air quality of each building. • Occupancy, lighting, and equipment gains are assumed at the same rate per square metres for both mosques.

6. Conclusions Human thermal comfort depends on the surrounding environment, the built environment, or the human body itself. The research focused on the built environment performance in a case of two different mosques. The research methodology employed was a building Buildings 2021, 11, 314 18 of 20

thermal simulation software, Tas Engineering, which analysed both mosques’ building thermal performance. This was an interesting research to conduct given that one mosque is a traditional mosque built in the 1600s and the other is a contemporary mosque built in 2015. They have different construction and environmental characteristics, but mosques buildings in general are simple and similar in design. The research aim is to compare between traditional and contemporary mosques’ thermal performance. The comparison between Hudhayfah and Al Wafi mosque indicate Al Wafi mosque has more consistent DBT in a free running mode during winter, and lower DBT when air conditioning is not operating during summer. Hence, it can be implied that Al Wafi mosque’s building has a better thermal performance in free running mode. Hudhayfah mosque building, on the other hand, showed less cooling load demand per area, which indicate a better thermal performance in air conditioning mode than Al Wafi mosque building. The results of the energy modelling simulations show that buildings are controlled by a set number of parameters that need to be studied collectively to achieve optimal thermal efficiency in buildings. Recent literature has shown that there are a number of improvements that can be made to the building by altering or changing the building’s design, orientation, materials, fenestration, building envelope insulation, and thermostat set point. Seven more simulations were conducted with different improvements in each case to the validated base model of each mosque. Hudhayfah and Al Wafi mosques have seen cooling load savings of up to 6% and 9%, respectively, by increasing the thermostat set point by 2 ◦C. Insulating the roof also yielded a substantial cooling load saving of up to 7% and 4%, respectively. On the other hand, when exchanging the building envelope material between both mosques by using clay roof and wall in Hudhayfah mosque and using concrete roof and walls in Al Wafi, it yielded in an increase in cooling loads of 7% and 13%, respectively. This could mean that traditional mosques were designed to be passively cooled, while contemporary mosques were designed to be actively cooled.

Author Contributions: Conceptualization, M.G. and H.A.R.; methodology, M.G. and H.A.R.; software, H.A.R.; validation, H.A.R.; formal analysis, H.A.R.; investigation, H.A.R.; resources, H.A.R.; data curation, H.A.R.; writing—original draft preparation, H.A.R.; writing—review and editing, M.G. and H.A.R.; visualization, H.A.R.; supervision, M.G.; project administration, H.A.R.; funding acquisition, H.A.R. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Data Availability Statement: The data that support the findings of this study are available from the corresponding author, H.A.R., upon reasonable request. Conflicts of Interest: The authors declare no conflict of interest.

Abbreviations

AC Air Conditioning CL Cooling Load (Watts) DBT Dry Bulb Temperature (◦C) DX System Direct Expansion System EPW EnergyPlus Weather File IES VE Integrated Environmental Solutions Inf/Vent Gain Inﬁltration/Ventilation heat gain (Watts) Tas Thermal Analysis Software TMY Typical Metrological Years

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