Ventilation Study in Achieving Thermal Comfort at Ice Cream Café in Malang City

. — Café is a retail F&B place for eating and drinking fast food and presenting a relaxed or informal atmosphere. Café, which is a public space where customers spend time, of course, must maintain ventilation in the café to ensure the customer's thermal comfort. For this reason, paying attention to air circulation in the cafe is essential. The author takes the ice cream cafe in Malang as the case study object in this case study research. This research focuses on ventilation on the first floor of the café. After making observations, it was found that the air circulation in the cafe is not smooth and limited because of the closed space. Despite having two air conditioners running, the restaurant's atmosphere started to feel limiting as the survey was being conducted. The lack of ventilation in this enclosed room further reduces the café's thermal comfort. To solve this problem, the author provides a solution for implementing cross-circulation by adding windows to the front and back of the café to maximize air circulation and using an exhaust fan in the café kitchen to maintain air quality. So with this, it can guarantee the thermal comfort of customers at this cafe.


Introduction
A cafe is a drinking place where visitors can order coffee, tea, pastries, snacks other non-alcoholic beverages [1].Cafes can be used for informal learning and are handled commercially with a relaxed atmosphere and without following the same rules and providing the same services as restaurants [2].The target market for cafes is usually young people or students with a price range that tends to be cheap.The cafe presents a relaxed atmosphere with service for an average of 24 hours.Currently, cafes are just some places that specifically serve coffee.One of the popular treats at cafes is ice cream.
There are many cafes whose menu focuses on selling ice cream, for example, this Cafe located in Malang city on Jl.Raya Sawojajar, Sawojajar, Kedungkandang, Malang.This cafe sells various kinds of milk-based drinks, tea, and coffee.However, the main menu that this cafe sells is ice cream.This cafe has an area of 12x4 m2.This cafe is located between two other shops, so the windows and doors are only in the front and back of the restaurant, which causes air circulation in this cafe to be disturbed.
Openings in the room allow for air exchange and light entry.Openings can be doors, windows, vents, and so on.Air conditioning in the room is essential.The factors that affect thermal comfort are air humidity, air temperature, wind speed, clothing, and activity [3].The absence of openings or air circulation will cause the air quality to become stuffy, damp, and unpleasant [4].In addition, the low quality of air ventilation can cause air trapping in the room.This Cafe located in Malang city has operating hours from 11.00 to 21.00.The target market for this Cafe is small children and young people who like ice cream, and the average visitor who buys ice cream will eat on the spot and spend a long time at Ice Cream Cafe.Air quality in the room is essential for the health of visitors.Humans spend 90% of their time indoors and continuously inhale the particles in the room.Therefore, poor room conditions can cause sick building syndrome, namely user-related illnesses such as asthma, fatigue, irritation, and headaches [5][6][7].

Ice cream cafe
Restaurants and café are the industry segments that provide accommodations and food and beverages (F&B), while café itself is a retail F&B place for eating and drinking fast food and presenting a relaxed or informal atmosphere [1,8].Currently, the Cafe is not just a place to eat and drink but also to gather and socialize while enjoying the available food and drinks [9].The Cafe can attract visitors by taking an exciting and conceptual atmosphere.There have been many kinds of cafes, such as ice cream.Now Ice cream is served in various flavours, shapes, and colours that are more varied with a more attractive presentation.So many people prefer ice cream as a refreshing snack.The background of these needs and desires, the ice cream business sector has developed and is in great demand by the public.The lifestyle development made the ice cream business create a new image; the idea emerged to build a cafe or restaurant that offers various types of ice cream [10].That way, the ice cream is an innovation from a café that serves different variations of ice cream on its menu.

Ventilation
Ventilation is an effort to renew indoor air through artificial ventilation and natural ventilation with the best possible arrangements to achieve the goal of health and comfort in space.The amount of fresh air intended helps reduce the air vapor content, eliminating the smell of sweat and carbon dioxide gas.And the amount/capacity of fresh air depends on the occupants' activities.For each different number of civitas, the air supplied will be more significant [11].Indoor ventilation is a thermal condition in a building (temperature, humidity, wind speed, and solar radiation) affecting the thermal conditions inside the building [12].Ventilation is divided into two, namely natural ventilation and mechanical ventilation [13].

Natural ventilation
Natural ventilation is a method for creating a passive cooling design in a structure that involves circulating the air inside it with open structural components [14].Air circulation well inside the building can provide comfort.Airflow can accelerate the evaporation process on the skin's surface, giving coolness to building occupants [15].Natural ventilation can provide comfort for building occupants when ventilation is optimal in terms of placement, size, and type.Ventilation must make building users comfortable with natural lighting and ventilation [16].By SNI, the opening area of a building is at least 5% of the total area of the building.Setting the building area is done so that the incoming air is not too much and not too little [17].

Mechanical ventilation
Mechanical ventilation systems in the buildings are intended to supply conditioned air to meet indoor climatic and energy needs [18].Mechanical ventilation here means that the air in the room is conditioned based on the heat load that occurs in the room using air conditioner (AC) technology.But the more people in the room, the greater the AC power needed because the human body expends quite a lot of calories, as well as the area of the room.And so on in human skin [19].

Effect of room temperature
Human reactions to environmental temperature are different for each individual, whereas, in an architectural sense, naturally, psychological responses to the influence of space can be determined [20].An increase in room temperature can result in (1) a feeling of fatigue followed by a loss of mental and physical work efficiency; (2) heart rate increases; (3) increased blood pressure; (4) the activity of the digestive system decreases; (5) core body temperature increases; (6) blood flow to the skin also increases; and (7) sweat production increases so that this situation triggers a decrease in student concentration in learning, mainly supported by free course credits, sitting position, level of class noise and the way lecturers present lecture material [21].

Air circulation
Air circulation replaces air in a room by entering the atmosphere from outside and removing the air inside.Homes need adequate airflow.You do this by creating proper air ventilation [7,22].Air circulation is scientifically necessary for interior design; air circulation is required not only for thermal comfort [23].One of them is by adding windows and ventilation to the room.To ensure circulation or replacement of air in and out more smoothly.

Exhaust fans
Indoor air conditioning is crucial.This Indoor air conditioning can reduce sick building syndrome (SBS), which can interfere with occupant activities.One way to condition the air is with mechanical ventilation [17].The benefits of using an exhaust fan, helps remove excess moisture, lowers room temperature, helps remove smoke and odors, improves thermal comfort, and keeps the room air cool [3,4,10,11,24].

Methodology
This research is qualitative research using the case study method.This research is focused on case studies of ventilation problems at Ice Cream Cafe retail.The case study was conducted by observation on November 2022 till January 2023.At the time of word, it was discovered that the second floor of this Cafe was being renovated, so it was inaccessible.So that in this study, the authors will only evaluate ventilation and air circulation on the first floor of this Cafe.With this observation, the authors obtain existing data and documentation of the object of this case study.As well as getting direct experience of feeling the air and evaluating thermal comfort at this Cafe.In addition, to maximize this research.
After making observations at Ice Cream Cafe, the author analyzes the location and size of this café space to create a floor plan.While researching, the author found a problem where the air circulation in the café is not smooth and limited because of the closed space.The air in the cafe gradually felt stuffy even though two air conditioners were used, but during the survey, only one air conditioner was used.In addition, the closed space without ventilation makes the thermal comfort in this café even worse.This is increasingly felt when leaving the cafe and again regarding the cool air outside.
Based on the analysis of the problems found, the authors provide a solution to facilitate air circulation in this Cafe by creating cross-circulation using windows on the front and back of the café so that air circulation can flow smoothly from both sides.Because the café is in a shop complex, the right and left sides cannot be given windows because they are connected to the shop next door.In addition, the authors added exhaust fan technology to maintain the temperature and air quality in the cafe.The author can solve the problems in the Ice Cream Cafe with this solution.

Existing ventilation study
Observational studies were carried out in the afternoon from 15.00 to 17.00 WIB.From the results of this observation, the experience of ventilation in this place is where the room feels stuffy, and there is no air circulation, so the air feels stuffy and hot.Place condition affects the taste and causes visitors to feel uncomfortable in the room for a short time, so they prefer take-away.Then, from this observation, an existing floor plan is obtained, which shows the ventilation conditions of the kitchen, the placement of the air conditioner, and the types of windows in this object.The existing ventilation scheme can be seen in Fig. 1.
The layout plan shows that the kitchen area is not equipped with an exhaust fan which causes the temperature in this area to feel hot and stuffy.In addition, the placement of the AC is close to the entrance area in a direction not facing the dine-in area, which causes the temperature in the room to increase so that it does not achieve thermal comfort.The type of fixed window makes hot air trapped in the room.
From our observations using a room temperature measuring instrument, the average temperature for six days at this Cafe is 26°C with the highest temperature at 26.8°C and the lowest temperature at 25.5°C as seen in Fig. 2. The Ice Cream Café has a dead window that closes because the ventilation focuses on artificial ventilation using an AC cooling machine.The air circulation that occurs is very limited and only occurs when the café door is opened.This results in the air flow rate in the café being 0 m3/s, while the area of the existing opening is as follows: • Sliding window area: 0. We learned from the data we collected for 24 hours x 6 days that the room is at a low temperature when the cafe is open, namely 9-21 hours.On 12th January 2023, at 9 a.m. on the second day of data collection, the air temperature was 26 degrees Celsius, or 1.1 degrees lower, 24.9 degrees Celsius.This drop in temperature signals that the air conditioner is beginning to activate, lowering the room temperature.At 10 a.m., the temperature had fallen to 24.9 degrees Celsius.However, due to the influence of the outside temperature, the air temperature rises to 25.2 at 11-17 o'clock, affecting the indoor temperature.When the sun sets at 18 o'clock, the weather outside begins to cool, and the interior temperature drops to 23.7 degrees Celsius.When the operating hours terminate at 21.00, the air conditioner is shut off, causing the room temperature to rise to 27 degrees Celsius.Based on the graph, it is clear that the air conditioning in the room is active during operating hours.Figure 3 depicts the temperature of the research object during 24 hours.

Added motion sensor cooker hood to the kitchen
Ice Cream Cafe needs to increase air circulation and temperature.It is necessary to add an exhaust fan to maximize the air exchange that occurs in the kitchen, as represented in Fig. 4-6.Meanwhile, to save energy by using the exhaust fan, a motion sensor system is implemented to make the exhaust fan work automatically during the cafe's operational time.Authors in previous studies have also researched using motion sensors for energy saving [25,26].However, the main difference is that prior studies focused on lighting energy, but current research focuses on ventilation.The exhaust fan capacity needed in the kitchen can be written using the following formula:

V=(P)(L)(T)
( ACH=15 times per hour From these calculations, the kitchen area requires an exhaust fan capacity of 345.6 m3/h.These calculations can be achieved by placing one exhaust fan in the kitchen.The required exhaust fan is a type of cooker hood.Concerning several products, the exhaust fan with a capacity of 350 m3/h (CMH) affects the appearance of noise, which is equal to 39 dB.This sound is equivalent to the sound of a refrigerator with a noise of 40 dB.Thus, a cooker hood of 350 CMH can be applied to the kitchen and does not have a too significant sound disturbance.

Application of cross circulation
The front window of Café is a wide dead glass in its present condition.Expansive windows can improve daytime lighting but do not affect natural ventilation.According to our observations, the air feels cleaner when someone opens the door.As a result, the author hypothesizes that this shop needs a live window in the front.Furthermore, if it implements cross ventilation, as previous research proposes, this shop will have good natural ventilation.
Cross circulation occurs when there are two parallel openings, so air exchange occurs, but this did not happen in the Ice Cream Cafe room.This type of fixed window type is the cause of air exchange not occurring, and improper placement of AC causes a waste of electrical energy.
In this scheme, it is possible to produce air exchange by changing the type of window in the entrance area to a swing window and an upward sliding window in the rear area, as seen in Fig. 7.The occurrence of this cross circulation makes the air cool so that customers are comfortable doing activities in the room.With this, thermal comfort can be achieved.According to Norbert Lechner, a minimum window area is 20% of the floor area for comfortable ventilation, and the area of the opening is also 20% of the wall area, which the equation can write Area opening = 20% (wall area) (1) The rear side has dimensions of 1.2 meters by 3 meters.Thus, the standard rear opening is 0.2 x 1.2 meters x 3 meters, producing 0.72 m2.The area of the window resulting from the design solution is 0.4 meters x 1.8 meters and produces a value of 0.72 m2.The numbers in this window already meet the specified standards.
The side of the entrance area has a different number, with a wall width of 4 meters and a wall height of 3 meters.Thus, 20% of the area of the entrance area is 0.2 x 4m x 3m and produces a figure of 2.4 m2.In this café, there are four windows with a width of 1.6 m and a height of 1.5 meters.Thus, the opening at the entrance is 0.2 x 1.6 m x 1.5 m x 4 pieces and produces 9.6 m2.This figure already meets the opening requirements.
So, the total window area of the design solution at the café meets the SNI standard, namely 5% x Building area.This cafe is 12 meters long and 4m wide.So that 5% of the area of the café is 0.5 x 12 m x 4m and produces 2.4 m2.Meanwhile, the total window area resulting from the design solution in the café is 0.72 m2 plus 9.6 m2, which is 10.32 m2 and meets the standards.
The amount of air flowing into the building also needs to be calculated.The calculation of the flow rate of air entering through the cafe window can be written as follows.Qp = Cv (A), (v) ( 1 ) Cv: Aperture effectiveness (0.30) (0.5-0.60 if the direction of the wind is perpendicular to the opening, 0.25 -0.35 if the window diagonal direction) (2) Qp: Air flowing through the window (m3/s) (3)

A:
Window area (4) V: 2m/s (5) The sliding window has dimensions of 0.4 m wide and 1.8 m high.Regarding the above equation, the air flowing through the window is 0.432 m3/s.On the other hand, the swing window has dimensions of 2.4 meters wide and 2 meters high, and the air flowing through the window is 1.44 m3/s.So, the initial air flow rate is 0 m3/s to 0.432 m3/s on the sliding window and 1.44 m3/s on the swing window.
The author's proposal to replace dead windows with living windows introduces natural ventilation in the form of cross ventilation.The author's recommendations will have additional consequences, such as noise or outside air pollution.It is due to the cafe's location on the outskirts of the major road.The combined effect of the two pollutants necessitates further research.

Conclusion
This research provides a solution to the ventilation problem at this Cafe by using an exhaust fan to exchange the air in the kitchen to maintain air quality and maximize ventilation not only in the kitchen but also affect the café room.An exhaust fan capacity of 345.6 m3/h is required.With this solution, it is hoped that it can overcome ventilation problems at this Cafe and provide thermal comfort to customers.
The next solution is to implement cross circulation using a sliding window at the back and a swinging window at the front of the café.So with this, it can maximize and expedite the circulation of air entering and leaving from both sides.By the SNI standard 5% x Building area, with a result of 10.32 m2 (fulfilled) thus, the airflow rate is 0.432 m3/s on the sliding window and 1.44 m3/s on the swing window.That way, the ventilation of the café room will be cooler and not stuffy as before.Air circulation from this window can also provide an alternative for ventilation in the café besides artificial ventilation, which guarantees the customer's thermal comfort.