A Study on Thermal Comfort of the Change Room of

Public Bathhouse

Seonghoon Yoon1, Yekyeong Shin1

1Department of Architectural Engineering, Namseoul University,

Seonghwan-eup, Seobuk-gu, Cheonan-city, 31020, KOREA

{aquila, shinyk77}@nsu.ac.kr

Abstract. For the interior thermal environment of a public bathhouses, we

investigated the kind of thermal sensation that the user feels after a bath, as well

as the optimum floor surface temperature which can provide thermal comfort for

the user, before or after the bath. The results showed that the users felt a thermal

sensation corresponding to the PMV index of an average of 0.67, and the

metabolic rate was about 2.35[met] after a bath.

Keywords: Thermal comfort, PMV, Change room, Floor heating

1 Introduction

Public bathhouses, one of the representative multiuse facilities in Korea, are a facility

which has a user morphological feature of which the user will enter a sauna room or

bath with a high temperature, to take a bath for about 30 minutes to an hour. In addition,

in Korea, the floor heating (Ondol) system is universally used as the interior heating

method in the indoor areas including the public bathhouses. Therefore, in the winter

season, the users who have finished their baths in the public bathhouses, have a

relatively higher metabolic rate compared to their physical activity when they enter the

changing rooms which are being heated through floor heating, and the type of thermal

environment that is needed in the aspect of comfort has not been specifically

investigated under these special conditions.

This study investigated the conditions of the thermal environment for the changing

rooms in public bathhouses, and suggests the conditions of the physical thermal factor

in order to provide a pleasant thermal environment for the user.

2 Methods

In order to investigate the thermal environment conditions of the changing rooms while

the floor is being heated, we measured the physical factors of a male changing room in

a public bathhouse located in Cheonan-city for the calculation of PMV. However,

because there is no clear standard for the metabolic rate (MET) of a body after a bath

Advanced Science and Technology Letters Vol.140 (GST 2016), pp.236-239

http://dx.doi.org/10.14257/astl.2016.140.45

ISSN: 2287-1233 ASTL Copyright © 2016 SERSC

(sauna), we estimated the PMV value and used a method to inversely estimate the MET

which satisfies the PMV value. In other words, we analogized the PMV value through

the results of a survey done on 12 subjects about thermal sensation, and by putting in

the physical factors and CLO (index of the clothing insulation) through measurements,

we deducted the MET value, which would result in the estimated PMV value. Table 1

shows the measurement categories and Fig.1 shows the floor plan of the place used for

the study.

Table 1. Measurement Categories and the Measuring Instruments

Category Measurable Range Accuracy Model Name (Manufacturer)

Dry bulb temp. 0~50℃ ±0.6℃ SK-150GT

(SATO) Relative humidity 10~95% ±3%

Black bulb globe temp. 0~80℃ ±2℃

Air velocity 0~10m/s ±0.03m/s testo 480 (TESTO)

Surface temp. -30~300℃ ±2℃ testo 810 (TESTO)

Fig. 1. Floor plan of the place used for investigation

1) Measuring the Thermal Environment

In order to evaluate the thermal environment during the period of heating we took the

measurements on November 19, 2015, where every 10 minutes for an hour at a point

1.2 meters above the floor in the middle of the bathhouse changing room, the dry bulb

temperature, black bulb globe temperature, relative humidity, and air velocity was

measured and the average value was obtained. In addition, the CLO needed to calculate

the PMV was applied as 0, and using the following function, the black bulb globe

temperature was converted to the MRT(Mean Radiant Temperature).

MRT = 𝑇𝑔 + 2.35√𝑣(𝑇𝑔 − 𝑇𝑑) [℃] (1)

Where, 𝑇𝑔 : black bulb globe temperature [℃] , 𝑇𝑑 : dry bulb temperature [℃], 𝑣 : air

velocity [m/s]

Advanced Science and Technology Letters Vol.140 (GST 2016)

Copyright © 2016 SERSC 237

2) Questionnaire

We conducted a survey as seen in Fig. 2, on twelve male users who entered the changing

room after a bath, asking them to tell us their current thermal sensations by choosing

one scale from the 7 steps scale.

Fig. 2. Survey Questions about Thermal Sensation

3 Results

1) Estimating the MET for those who have just took a bath.

The results of the measurements for the physical factors of the changing room were as

follows: the average of the dry bulb temperature was 26.1℃, the black bulb globe

temperature 27.3℃, the relative humidity 25.8%, the air velocity 0.4 m/s, and through

the conversion formula the MRT was calculated to be 29.1℃. Also, the average floor

surface temperature was 36.4℃.

Table 2 shows the results of the questionnaire, and by calculating the arithmetical

mean, the PMV of the changing room was estimated at 0.65.

Therefore, with the measured physical factors and CLO=0, we calculated the MET

that would be needed, in order to draw out PMV=0.67, and the value obtained was

2.35[met].

Table 2. Questionnaire Results

Subject no. 1 2 3 4 5 6 7 8 9 10 11 12

Thermal Scale -1 0 0 0 0 1 1 1 1 1 2 2

2) Examination of the Optimum Thermal Environment of the Changing Room

A changing room is an area where those who come to take a bath and those who have

just finished their bath coexist. For the CLO and MET according to the user's condition,

the following two conditions were estimated to examine the MRT and floor surface

temperature needed in order to develop a pleasant PMV condition.

Advanced Science and Technology Letters Vol.140 (GST 2016)

238 Copyright © 2016 SERSC

Table 3. CLO and MET Conditions

Case No. User's Condition CLO MET

Case 1 Before the Bath 0 1.6 (standing, light work)

Case 2 After the Bath 0 2.35 (after bath, sauna)

In order for the measured physical factors and the results by applying CLO and MET

in table 3, to be within the thermal comfort PMV range -0.5~+0.5 by the ISO 7730, the

MRT was calculated, and in Case 1 it was 29.6℃ (PMV= -0.484) and in Case 2 it was

27.8℃ (PMV=+0.500). Here, the wall and ceiling surface temperature was estimated

to be the same as the air temperature of the middle of the room, and by using the

following formula, the floor surface temperature (𝑇𝑓𝑙𝑜𝑜𝑟) which could satisfy the MRT

value in Cases 1 and 2 was calculated.

𝑀𝑅𝑇 =𝑇𝑤𝑎𝑙𝑙×𝐴𝑤𝑎𝑙𝑙+ 𝑇𝑐𝑒𝑖𝑙𝑖𝑛𝑔×𝐴𝑐𝑒𝑖𝑙𝑖𝑛𝑔+ 𝑇𝑓𝑙𝑜𝑜𝑟×𝐴𝑓𝑙𝑜𝑜𝑟

𝐴𝑤𝑎𝑙𝑙+ 𝐴𝑐𝑒𝑖𝑙𝑖𝑛𝑔+ 𝐴𝑓𝑙𝑜𝑜𝑟 [℃] (2)

Where, 𝑇𝑤𝑎𝑙𝑙, 𝑇𝑐𝑒𝑖𝑙𝑖𝑛𝑔, 𝑇𝑓𝑙𝑜𝑜𝑟 : wall, ceiling, floor surface temperature, respectively

[℃] ,

𝐴𝑤𝑎𝑙𝑙 , 𝐴𝑐𝑒𝑖𝑙𝑖𝑛𝑔, 𝐴𝑓𝑙𝑜𝑜𝑟 : wall, ceiling, floor area, respectively [㎡]

Calculations showed that in Case 1, the floor surface temperature was 35.7℃ and in

Case 2 it was 30.8℃. Though it is hard to satisfy users both before and after a bath, we

determined that maintaining the floor surface temperature within the range of about

31~35℃, would generally enhance thermal comfort.

Acknowledgments. Funding for this paper was provided by Namseoul university.

References

1. ISO 7730-2005, Ergonomics of the thermal environment - Analytical determination and

interpretation of thermal comfort using calculation of the PMV and PPD indices and local

thermal comfort criteria (2005)

2. ANSI/ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy,

(1992)

3. Calucation of Predicted mean Vote and Predicted Percentage Dissatisfied,

4. http://www.eat.lth.se/fileadmin/eat/Termisk_miljoe/PMV-PPD.html

Advanced Science and Technology Letters Vol.140 (GST 2016)

Copyright © 2016 SERSC 239