On the conformity of floor heating systems with sleeping in the eastern-style beds; physiological responses and thermal comfort assessment

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Building and Environment 47 (2012) 322e329

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Building and Environment

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On the conformity of floor heating systems with sleeping in the eastern-stylebeds; physiological responses and thermal comfort assessment

Mehdi Maerefat a, Alireza Zolfaghari a,*, Amir Omidvar b

aDepartment of Mechanical Engineering, Tarbiat Modares University, Tehran, IranbDepartment of Mechanical and Aerospace Engineering, Shiraz University of Technology, Shiraz, Iran

a r t i c l e i n f o

Article history:Received 8 March 2011Received in revised form30 June 2011Accepted 9 July 2011

Keywords:Radiant floor heatingSleepEastern-style bedsThermal sensationPhysiological response

* Corresponding author. Tel.: þ98 21 82 88 33 60.E-mail address: [email protected] (A.

0360-1323/$ e see front matter � 2011 Elsevier Ltd.doi:10.1016/j.buildenv.2011.07.008

a b s t r a c t

Radiant floor heating systems are usually designed in such a way that the sedentary persons feel thermalneutrality. On the other hand, inmost of eastern countries, people traditionally tend to directly sit or sleep onthe floor. This could arise some limitations in using of the floor heating systems in the countries with sucheastern lifestyle. The main focus of this study is on evaluating the physiological responses and thermalcomfort of sleeping persons in an eastern-style bed on a heated floor. For this purpose, thermal sensation ofsleepingoccupants on theheatedfloorwas comparedwith that of sleepingpersons on the conventional beds.The results reveal that under similar thermal conditions, the thermal sensation and skin wettedness of thesleeping persons are obviously higher on the eastern-style beds than on the conventional beds. Therefore,sleeping in an eastern-style bed causes the person to feel more thermal discomfort and also moreunpleasantness due to skinwettedness. Furthermore, the results indicate that to get the same level of thermalandwettedness pleasantness on both aforementioned beds, the thermal insulation value of the blanketmustbe about 0.4 clo lower in the eastern-style bedding arrangement than in the conventional bed.

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1. Introduction

In recent years, there has been growing interest in using radiantfloor heating systems because of their considerable advantages suchas energy-saving and comfortable thermal environment [1e4]. Inthese systems, a significant part of heat energy is transmitted inradiant mode [5e7]. Therefore, the human body thermal conditionscan be considerably influenced by changing the body posture andthe view factor between the heated floor and the human body. Onthe other side, inmost of eastern countries, people traditionally tendto directly sit or sleep on the floor. Moreover, the floor heating andthe other air-conditioning systems are commonly designed based onthermal neutrality of the occupants with sedentary conditions. Thiscan impose some limitations in using of the floor heating systems forthe people with such eastern lifestyle. In this paper, investigationsare made to knowwhether the floor heating systems are convenientfor the persons who tend to sleep traditionally on the floor, and howthe thermal and physiological responses of the human body areaffected under the mentioned conditions.

In the last few years, many researches have investigated theeffects of body posture on thermal condition of the human body in

Zolfaghari).

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a radiant heated environment [8e12]. Almost all of these studieswere performed for a Korean traditional floor heating systemwhichis called Ondol. Song [10e12] extensively investigated the thermalsensation and physiological parameters of the persons that sat onOndol. Moreover, in 1993, Choi [8] experimentally studied the bedclimate and the physiological response during sleep on Ondol. Butin the mentioned study, the thermal sensation of occupants andtheir thermoregulatory responses such as regulatory sweating andskin wettedness have not been investigated.

In the present study, we attempt to investigate the thermalsensation and the physiological response of a person during sleepon a heated floor by using a convenient thermal comfort model.Since 1970, many thermal comfort models have been developed onthe basis of the human body energy balance equations. Theseinclude the simplified thermal comfort models (such as Fanger [13]well-known model and Gagge’s model [14]) and complex multi-segmented models. The first multi-segmented model of thehuman body was developed by Stolwijk [15]. Afterward, severalimproved multi-segment models have been developed in theliterature. These include the Berkeley Comfort Model [16e20] andthe models discussed by Tanabe et al. [21], Kaynakli et al. [22,23],Yigit [24,25], Fiala et al. [26], Yi et al. [27], Fengzhi and Yi [28], andSalloum et al. [29]. But, to apply a complexmodel, a large amount ofempirical data is required to simulate each segment of the body.Also, the data must be numerically analyzed to determine the

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M. Maerefat et al. / Building and Environment 47 (2012) 322e329 323

thermal parameters of each segment and its subdivided layers.Hence, the complex models could not be employed in thermalcomfort standards where the utilization of the complex models isextremely limited. Therefore, among the mentioned models, onlytwo have commonly been used to evaluate thermal sensation [30].Fanger’s steady-state model [13] and Gagge’s two-node transientmodel [14] are the exclusive thermal sensation models that havebeen employed in thermal comfort standards [31,32]. But, it shouldbe noted that the mentioned models are not exclusively developedfor sleeping thermal conditions. Nevertheless, the body thermalconditions in the sleep duration are distinctly different fromsedentary conditions because of decreasing in the metabolic rate,increasing in portion of conductive heat transfer and alsoincreasing of the thermal resistance between the body and theenvironment. In the last few years, Lin and Deng carried out anextensive research on sleeping thermal environment [33e38]. In2008, they developed a new thermal comfort model for sleepingenvironments on the basis of Fanger’s model [36]. But in theirsteady-state model, the thermoregulatory mechanisms such asregulatory sweating and vasomotion have not been considered.Furthermore, the effects of conductive heat transfer have not beentaken into account in the energy balance equations of thementioned model. In addition, although the previous studies[39e42] have shown that the sensation of bare and covered parts ofthe body may be significantly different, the model of Lin and Deng[36] has considered the human body as one node. As reported inthe literature [43e50], the body thermal conditions during sleepcan be significantly affected by the covering. It was reported thatthe range of thermoneutral temperature during sleep is 28e32 fornaked body [43e48] and 20e22.2 �C for covered body [49,50].Thus, the thermal conditions of bare and clothed parts of the bodymust be considered separately. Recently, Zolfaghari and Maerefat[51] have introduced a new 3-node thermal comfort model on thebasis of Gagge’s transient model. In this model, the physiologicalparameters and thermoregulatory mechanisms of the human bodyare considered. Moreover, the mentioned model is able to predictthe thermal sensation of bare and covered parts of the human body,separately. Consequently, it seems that the 3-node model can beutilized for evaluating the sensation and physiological response ofthe human body during sleep.

2. The simplified 3-node model

In our previous study [51], a simplified three-node and easy-to-implement thermal sensation model was presented based onGagge’s standard model. The verification results have shown thatthis model can accurately estimate the thermal sensation of thebare as well as the covered parts of the body. This model uses threeenergy balance equations for the bare skin, covered skin and thecore to evaluate the thermal comfort conditions of the human body.

Scr ¼ ð1� aÞmCp;bAD

dTcrdt

(1)

Ssk;br ¼ mamCp;blAD

dTsk;brdt

(2)

Ssk;cv ¼ ð1� mÞamCp;bð1� lÞAD

dTsk;cvdt

(3)

where, br and cv subscripts are related to bare and clothed skinparts and also Scr, Ssk,br and Ssk,cv are the heat storage rate in thecore, bare skin and covered skin compartments, respectively. In

addition, l is the ratio of the bare skin surface area (Abr) to the totalsurface area of body (AD)

l ¼ AbrAD

(4)

Moreover, the ratio of the bare segments mass (mbr) to the bodymass (m) is defined as follows

m ¼ mbrm

(5)

The details for calculation of l and m can be found in Ref. [51].In many thermal comfort studies, the heat conduction between

the body and environment is neglected due to its insignificanteffect on thermal balance of the human body under manyconventional thermal conditions [52]. Also, the conductive heatloss from the body is not considered in the simplified 3-nodemodel[51]. But, for a sleeping person, the contact area between thehuman body and bedding system is significant. Therefore,a conductive term must be implemented in the heat balanceequations in order to considering conduction heat transfer betweenthe body and the bedding system. Consequently, the heat storagerate in the core, bare skin and covered skin compartments can becalculated as follows:

Scr ¼ M �W � Qres � l Qcr�sk;br � ð1� lÞQcr�sk;cv (6)

Ssk;br ¼ Qcr�sk;br��Qcond;brþQconv;brþQrad;brþQevap;br

�(7)

Ssk;cv ¼ Qcr�sk;cv��Qcond;cvþQconv;cvþQrad;cvþQevap;cv

�(8)

where and Qres, Qcond, Qconv, Qrad and Qevap are respiratory,conductive, convective, radiative and evaporative heat loss fromskin, respectively. Respiration causes two forms of heat exchangewith the environment: dry heat loss and latent heat loss. The totalheat loss from respiration can be determined by

Qres ¼ 0:0014Mð34� TaÞ þ 0:0173Mð5:87� PaÞ (9)

The conductive heat losses from bare and covered skin arecalculated as follows

Qcond;br ¼lbed

�Tsk;br � Tf

�

Rbed(10)

Qcond;cv ¼lbed

�Tsk;cv � Tf

�

Rbed þ Rcl(11)

where, lbed is the fraction of the skin surface that is in contactwith the bed and it can be obtained from Ref. [53]. Moreover, Rbedand Rcl are the thermal resistance of the bed and clothing,respectively.

Also, the convective-radiative and evaporative heat losses frombare and covered skin can be calculated as follows

Qconv;br þ Qrad;br þ Qevap;br ¼ ð1� lbedÞ

0B@�Tsk;br � To

�Rt;br

þLRwbr

�Psk;brðsÞ � Pa

�

Rt;br

1CA (12)

Table 1Comparison of the 3-node model results for skin and core temperature with theexperimental data of Choi [8].

Simulatedresults of the3-node model

Experimental dataof Choi [8]

Difference betweenthe simulated andempirical data

Covered skintemp. (�C)

35.3 35.2 0.1

Mean skintemp. (�C)

34.7 34.9 0.2

Core temp. (�C) 36.8 36.6 0.2

Fig. 1. Schematic of sleeping in an eastern-style bed on the heated floor.

M. Maerefat et al. / Building and Environment 47 (2012) 322e329324

Qconv;cvþQrad;cvþQevap;cv ¼ ð1�lbedÞ

0B@�Tsk;cv�To

�Rt;cv

þimLRwcv

�Psk;cvðsÞ �Pa

�

Rt;cv

1CA (13)

In addition, the rates of the heat transfer from the core to thebare and covered skin can be estimated by

Qcr�sk;br ¼�Keff þ Cp;bl _mbl

��Tcr � Tsk;br

�(14)

Qcr�sk;cl ¼�Keff þ Cp;bl _mbl

��Tcr � Tsk;cl

�(15)

It should be noted that a, wbr, wcv and _mbl depend on the ther-moregulatory mechanisms of the human body and they are definedon the basis of cold/warm signals of the human body. Additionalinformation for calculation of these thermoregulatory parameterscan be found in Ref. [51].

After calculating the temperatures of each body compartmentthermal sensation indices are defined as follows

TSENSbr ¼8<:0:4685

�Tb;br�Tb;c

�Tb;br<Tb;c

0:47he;br�Tb;br�Tb;c

��Tb;h�Tb;c

�Tb;c�Tb;br�Tb;h

0:47he;brþ0:685�Tb;br�Tb;h

�Tb;h<Tb;br

(16)

TSENScv ¼8<:0:4685

�Tb;cv�Tb;c

�Tb;cv < Tb;c

0:47he;cv�Tb;cv�Tb;c

��Tb;h�Tb;c

�Tb;c � Tb;cv � Tb;h

0:47he;cvþ0:685�Tb;cv�Tb;h

�Tb;h < Tb;cv

(17)

TSENSov ¼8<:

0:4685�Tb � Tb;c

�Tb < Tb;c

0:47he�Tb � Tb;c

��Tb;h � Tb;c

�Tb;c � Tb � Tb;h

0:47he þ 0:685�Tb � Tb;h

�Tb;h < Tb

(18)

where, TSENSbr, TSENScv and TSENSov are, respectively, the thermalsensation of bare parts, covered parts,and overall body. In addition,Tb,br, Tb,cv and Tb are defined as

Tb;br ¼ a Tsk;br þ ð1� aÞTcr (19)

Tb;cl ¼ a Tsk;cl þ ð1� aÞTcr (20)

Tb ¼ a Tsk;ov þ ð1� aÞTcr (21)

and

Tsk;ov ¼ lTsk;br þ ð1� lÞTsk;cl (22)

Also,

Tb;c ¼ 0:194ðM �WÞ þ 36:301 (23)

Tb;h ¼ 0:347ðM �WÞ þ 36:669 (24)

By using above relations, we can evaluate the thermal sensation(TSENS) of the bare and covered parts of the body, separately. Itshould be noted that the TSENS index is based on 11-pointnumerical scales, as follows: þ5 intolerable hot, þ4 very hot, þ3hot, þ2 warm, þ1 slightly warm, 0 neutral sensation, �1 slightlycool, �2, cool, �3 cold, �4 very cold, �5 intolerable cold [52].

3. Validation

In order to validate the 3-node model for sleeping thermalenvironment, the simulation results are compared with theexperimental data reported in Ref. [8]. Choi [8] measured the skinand rectal temperature of four healthy women while they weresleeping on Ondol floor heating system for 7 h. In the mentionedstudy, the Ondol floor surface was controlled at a temperature of29 � 1 �C and the indoor environment was 23.1e24.3 �C/60 � 3%RH. In Table 1, the obtained results of the 3-nodemodel for skin andcore temperature are compared with the experimental data of Choi[8]. As it shown in Table 1, the 3-node model is able to accuratelypredict the thermal conditions of the human body during sleep.

4. Methodology

In this paper, the conformity of floor heating systems withsleeping in the eastern-style beds is investigated by using thesimplified 3-node model. For this aim, we consider a person witha typical indoor clothing ensemble (Icl ¼ 0.8 clo) under sleepingcondition in an eastern-style bed on a heated floor. The floorsurface temperature is assumed to be 29 �C that is in good agree-ment with experimental values reported in [54]. The ambientrelative humidity is assumed to be 50% and the ambient tempera-ture is calculated in such a way that the sedentary persons feelthermal neutrality in the occupied zone. Fig. 1 shows a schematicrepresentation of a sleeping person in an eastern-style bed onheated floor. In this situation, the thermal sensation and physio-logical responses of the human body are evaluated for investigatingthe sleep quality of the occupants. Afterward, in Section 5.2, theinfluence of the bedding type on the sleep quality of the occupantsis investigated. For this aim, two main cases are considered:sleeping in an eastern-style bed (see Fig. 1) and sleeping ona conventional bed (see Fig. 2). In order to study the influence of thebedding type on the sleep quality, the thermal sensation andphysiological responses of the human body are compared for thesetwo cases. In all of these studies, it is assumed that the persons usea common eastern-style mattress for sleeping. The characteristicsdetails of the mentionedmattress have been reported in References[36,37]

Fig. 2. Schematic of sleeping on a conventional bed in a room with the floor heatingsystem.

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2

Thermal resistance of blanket (clo)

Th

erm

al sen

satio

n

covered

nude

overall

Fig. 4. Thermal sensation in relation to thermal resistance of the blanket for a sleepingperson in an eastern-style bed on the heated floor.


5. Results and discussion

People spend about one-third of their life sleeping. Therefore,investigation of the bedroom environment and sleep quality is veryimportant. The sleep quality intensely depends on the environ-mental and physiological parameters. Persons prefer to sleep underconditions that minimize the physiological effort of regulation fortheir body. In other words, the activation of the physiologicalthermoregulatory mechanisms such as sweating, vasodilatationand vasoconstriction can causes thermal unpleasantness forsleeping persons.

Understanding the trend of physiological adaptations would beinteresting to assess the effects of the bedding type on the sleepquality of a person who slept on a radiant heated floor. Whena person sleeps on the heated floor according to eastern lifestyle, themost of his/her body is in direct contact with the radiant floor or the

-2-1.5

-1-0.5

0

0.51

1.52a

b

0 30 60 90 120 150 180Time (min)

TSEN

S of

nud

e sk

in

Blanket resistance = 0.0 clo




-2-1.5

-1

-0.50

0.51

1.52

0 30 60 90 120 150 180Time (min)

TSEN

S of

cov

ered

ski

n





Fig. 3. Thermal sensation of bare (a) and covered (b) parts of the human body fora person who slept in an eastern-style bed on the heated floor.

heated mattress surface. This may causes an interruption in heattransfer processes between the human body and the environment.In these circumstances, the accumulated heat energy in the humanbody should be removed via physiological adaptation processes andthis can significantly affect the sleep quality. So, in order to estimatethe sleep quality for the person lied down on the heated floor, thephysiological thermal responses of the body should be monitored.Therefore, in the present study in addition to global thermalsensation, we focus on evaluating the adaptation indices such as coretemperature, skin temperature and skin wettedness.

5.1. Thermal responses of a sleeping person in an eastern-style bed

The thermal sensation of bare and covered parts of the body ofa sleeping person in eastern-style bed on heated floor is shown inFig. 3 for various thermal resistances of the covering blanket. It canbe seen that the thermal sensation of bare parts of the body alwaysremains in the acceptable region of thermal comfort. However,thermal sensation of the covered parts of the human body isconsiderably influenced by thermal resistance of the coveringblanket. As seen in the Fig. 3(b), undesirable thermal sensation dueto blanket thermal resistance is appeared in the initial stage of thesleeping period. The initial stage of sleep is a very light sleep, andthe slightest disturbance can wake the dreamer at this stage. Usingimproper blanket for sleeping in eastern-style bed on heated floorcan interrupt the whole sleep cycle and prevent the person toexperience the deep sleep. So, thermal resistance of the blanket isan effective parameter in evaluation of thermal sensation and sleepquality of the persons.

30

31

32

33

34

35

36

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2


skin

tem

peratu

re (°C

)

covered

nude

overall

Fig. 5. Relation between skin temperature and thermal resistance of the blanket fora sleeping person in an eastern-style bed on the heated floor.

0

0.1

0.2

0.3

0.4

0.5

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2


skin

w

etted

ness

covered

nude

overall

Fig. 6. Skin wettedness in relation to thermal resistance of the blanket for a sleepingperson in an eastern-style bed on the heated floor.

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2


Th

erm

al sen

satio

n

Case A

Case B

Fig. 8. Comparison between Case A and Case B: overall thermal sensation in relation tothermal resistance of the blanket.


Also, as shown in Fig. 3, the transition time of the humanthermal response is not large. After the person fell asleep, it takesabout 1 h for the body to reach steady-state thermal conditions.Therefore, in the following results, we will investigate the thermalconditions of the human body after this transition time.

Fig. 4 shows the thermal sensation in relation to thermalresistance of the blanket for a personwho slept in eastern-style bedon heated floor. From the results shown in this figure, it is evidentthat the thermal sensation of sleeping persons is strongly depen-dent on the thermal insulation value of the blanket. The resultsindicate that if the thermal insulation value of the blanket used inthe eastern-style bedding system is more than 0.2 clo, the thermalsensation of the covered parts of the human body may exceed thepermissible thermal comfort region. Also, it should be noted that

a

b

-2-1.5

-1-0.5

0

0.51

1.52

0 30 60 90 120 150 180Time (min)

TSEN

S of

nud

e sk

in





-2-1.5

-1

-0.50

0.51

1.52

0 30 60 90 120 150 180Time (min)

TSEN

S of

cov

ered

ski

n





Fig. 7. Thermal sensation of bare (a) and covered (b) parts of the human body fora person who slept on the conventional bed.

the initial abrupt change in Fig. 4 and the following figures occursdue to the thermal resistance of the air gap between the body andthe blanket.

As mentioned previously, in order to reach a high quality sleepthe thermal satisfaction of the body of dreamers is necessary butnot enough. For this aim, besides the analyzing the thermalsensation, the trend of fundamental adaptation parameters suchas skin temperature and skin wettedness should be checked.Fig. 5 shows the relation between the skin temperature andthermal resistance of blanket for a person who slept in aneastern-style bed on the heated floor. It can be seen that the skintemperature of covered parts of the human body is about 3 �Chigher than nude skin temperature during sleep under thementioned conditions.

a

b

30

31

32

33

34

35

36

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2


skin

tem

peratu

re (°C

)

Case A

Case B

36.0

36.2

36.4

36.6

36.8

37.0

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2


co

re tem

peratu

re (°C

)

Case A

Case B

Fig. 9. Comparison between Case A and Case B: overall skin temperature (a) and coretemperature (b) in relation to thermal resistance of the blanket.

0

0.1

0.2

0.3

0.4

0.5

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2


skin

w

etted

ness

Case A

Case B

Fig. 10. Comparison between Case A and Case B: overall skin wettedness in relation tothermal resistance of the blanket.


In Fig. 6, the relation between the skin wettedness and thermalresistance of the blanket is shown. It is clearly seen that the skinwettedness rises almost linearly with increasing thermal resistanceof the blanket. Moreover, the wettedness of nude skin is signifi-cantly lower than the wettedness of the covered parts of the body.For blanket thermal resistances of 0.2 and 2 clo, the skinwettednessof the covered parts of the body is respectively about two and fivetimes greater than that of the nude parts.

5.2. The influence of the bedding type

As mentioned previously, in order to investigate the influence ofthe bedding type on sleep quality of the occupants, two main casesare considered: “Case A-sleeping in an eastern-style bed” (Fig. 1)and “Case B-sleeping on a conventional bed” (Fig. 2). In these cases,a person with a typical indoor clothing ensemble (Icl ¼ 0.8 clo) isconsidered under sleeping condition in a roomwith a heated floor.The floor surface temperature is assumed to be 29 �C and the otherpersonal and environmental parameters are completely similar forthese two cases.

In Fig. 7, the thermal sensation of bare and covered parts of thebody of a sleeping person on a conventional bed is shown forvarious thermal resistances of the covering blanket. Also, Fig. 8shows a comparison between Case A and Case B for occupants’thermal sensation. It is seen that the persons exhibit a highersensibility to the blanket thermal resistance change during sleep inthe eastern-style beds. Also, as seen in Fig. 8, under similar personaland environmental conditions, the eastern-style sleeping personsalways feel warmer than the persons who slept on conventionalbeds. Moreover, for the blanket thermal resistance higher than 0.5clo, the thermal sensation of the eastern-style sleeping persons isalmost 0.5 units higher than that of the sleeping persons on theconventional beds. In addition, the results indicate that only for theblanket thermal resistance lower than 0.3 clo, the eastern-stylesleeping persons feel thermal comfort. In addition, it can be seenthat the thermal sensation of sleeping persons on conventional bedremains in thermal comfort region for the thermal resistance oflower than 0.8 clo.

In Figs. 9 and 10, the overall skin temperature, core temperatureand the overall skin wettedness for sleeping persons on the heatedfloor (Case A) are compared with that of sleeping persons on theconventional mattress and bed (Case B). As seen in Fig. 9, the skinand core temperatures for a sleeping person in an eastern-style bedare obviously more than that of sleeping person on a conventionalbed under similar conditions. This means that the heat accumula-tion has been occurred in the human body. In this situation, it isexpected that the body tend to prevent this via increasing the

sweating rate and then skin wettedness. It is worth pointing outthat the skin wettedness is more closely related to the sense ofdiscomfort or unpleasantness than to temperature sensation [52].As can be seen from Fig. 10, under similar conditions, the skinwettedness of a person who slept on a conventional bed is about0.07 lower than the skin wettedness of a person on the eastern-style sleeping arrangements.

The results indicate that under similar thermal conditions forthe floor heating and the bedding system, the sleeping persons feelmore thermal discomfort and also more wettedness unpleasant-ness in the eastern-style beds than in the conventional beds.Moreover, it should be noted that, in the present study, thetemperature of the heated floor is assumed to be about 29 �C asrecommended by Ref. [6]. But, it is evident that if the heated floortemperature exceeds the aforementioned value, the sleepingpersons perceive more critical thermal conditions on the eastern-style beds, and a reduction in the operating floor temperature toless than 29 �C may improve the thermal comfort conditions.

6. Conclusions

In this paper, the conformity of floor heating systems withsleeping in the eastern-style beds has been investigated by usingthe simplified 3-node model. The thermal sensation and physio-logical parameters of the human body has been evaluated in a roomwith floor heating system for two different conditions: sleeping inan eastern-style bed and sleeping on a conventional bed. The majorcontribution of the present study is to evaluate the thermalconditions for sleeping persons in an eastern-style bed andcompare it with that of sleeping persons on the conventional bed.

The main results of this study can be summarized as follows.

1. Under similar personal and environmental conditions, sleepingin an eastern-style bed causes the person to feel a warmerthermal sensation than the person who slept in the conven-tional bed.

2. In a room heated by radiant floor heating system, the sweatingrate and skin wettedness of the sleeping person is obviouslyhigher in the eastern-style beds than the conventional beds.High sweating rate during sleeping period is not a desirablesensation and can decreases sleep quality.

3. To get the same level of thermal and wettedness pleasantnesson both eastern-style and conventional beds, the thermalinsulation value of the blanket which is used in eastern-stylesleeping must be about 0.4 clo lower than that of used forsleeping on conventional beds.

4. When persons use the blanket as a covering during the sleepperiod, the thermal sensation of the eastern-style sleepingpersons is about 0.5 units higher than that of the sleepingpersons on the conventional beds.

Appendix. Nomenclature

AD DuBois surface area of nude body, (m2)Cp specific heat, (J/kg�C)im total vapor permeation efficiency of clothing system,

(n.d.)Keff effective conductance between core and skin, (W/m2K)LR Lewis ratio, (z16.5 �C/kPa)m body mass, (kg)M metabolic rate, (W/m2)_mbl rate of blood flow, (kg/m2s)Pa water vapor pressure in the air, (kPa)


Psk(s) water vapor pressure in the saturated air at the skintemperature, (kPa)

Q heat flow rate, (W/m2)Qcr-sk heat flow rate from core to skin, (W/m2)Rbed the total thermal resistance of mattress and bed

(m2 �C/W)Rcl the total thermal resistance of clothing system (m2 �C/W)Rt total sensible thermal resistance, (m2 �C/W)S heat storage rate, (W/m2)t time, (s)T temperature, (�C)TSENS thermal sensation, (n.d.)w skin wettedness, (n.d.)W external work done by the muscles, (W/m2)

Greek symbolsa fraction of body mass concentrated in skin compartment,

(n.d.)he evaporative efficiency (assumed to be 0.85), (n.d.)l ratio of the bare skin surface area to the total surface area

of body, (n.d.)lbed fraction of the skin surface that is in contact with the bed,

(n.d.)m ratio of the bare segments mass to the body mass, (n.d.)

Subscriptsa airb bodybl bloodbr barecv coveredcond conductiveconv convectivecr coreevap evaporativef floorn neutralo operativeov overallrad radiativeres respirationsk skin

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Documents

On the conformity of floor heating systems with sleeping in the eastern-style beds; physiological responses and thermal comfort assessment