The effect of garment combinations on thermal comfort of office clothing

Abstract

Clothing and the enclosed air layers highly affect heat dissipation from the body and thus, are crucial factors when it comes to thermal comfort. The heat and moisture transfer is affected by the variation of the size and the shape of air gaps between the garment and the human body. In addition, the fabric and garment design properties can affect the amount of heat loss from different body parts. In this study, we investigated the effect of fabric properties (different raw materials and weave types) and the garment fit on the heat loss through the garment combinations (undershirt and shirt) for the different parts of the upper body (trunk, chest, and back) using a sweating thermal manikin. The undershirt fit and the raw material of the shirts showed strong effects on the dry thermal resistance of the garment combinations. Moreover, the undershirt properties affected the evaporative heat loss from garment combinations, and the magnitude of these effects varied over different body regions. Whilst the undershirt fit had a significant impact on the evaporative heat loss of the back region, the influence of the undershirt raw material was more important in the chest region. The findings of this study provide fundamental knowledge to improve the thermal comfort of garment combinations for office wear.

Keywords

sweating thermal manikin thermal comfort office clothing dry thermal resistance evaporative heat loss garment combination

Clothing is a thermal and moisture barrier between the human body and the environment.¹ Heat transfer through clothing is a crucial parameter to maintain core body temperature and skin temperature, hence thermal comfort.² Three different forms of dry heat exchange, convection, conduction, and radiation, occur between the body and its environment.³ Dry heat transfer is mainly related to the thermal insulation and the air permeability of garments, and thereby air layers between the skin and the garment and among different garment layers.^4,5 Previous studies have revealed that clothing thermal insulation is largely affected by fabric structural and physical properties (e.g., fiber type, yarn type, fabric thickness, weave type),^6–10 garment properties (e.g., garment fit, closures and vents, joining method),^11–15 environmental conditions, and body movements.^16–21

In cases in which the heat exchange mechanisms are not effective enough to release heat from the body or even lead to heat gain of the body, heat accumulates in the body and affects thermal comfort and work performance.^13,22 Perspiration increases heat loss through evaporation, which is a crucial mechanism in cooling. Evaporative heat loss from the skin is dependent on the difference between the water vapor pressure in the environment and at the skin and is mainly related to the quantity of moisture on the skin.²³ Clothing highly affects sweat evaporative cooling on the skin. Therefore, it is crucial to determine the moisture absorption and transfer properties of garment layers in order to predict and control the cooling effect of evaporation on the skin.^24–27

The amount of heat loss from different body segments can differ due to the shape of the human body: heat loss depends on the variation in air gap size and shape below, between, and on top of the garment layers. Psikuta et al.²⁸ reported that the lower back and lumbus regions had higher air gap thicknesses than the abdomen because of their concave form. Air gaps are also affected by garment manufacture, design, and the mechanical properties of the fabric (e.g., drape coefficient, bending properties).^29–32 Mark³³ examined the effect of the outer garment in multilayer clothing combinations on the air gap thickness and the contact area. When the ease allowances of the undergarment were lower than those of the outer garment, the measured properties were similar for the undergarment scanned with and without the outer garment being worn because the outer garment did not compress the undergarment. Chen et al.¹¹ and Weder et al.³⁴ found that the thermal insulation of loose garment structures was approximately 30% greater than those of a more fitted structure.

Sweating thermal manikins, which imitate the anatomical shape of the human body, give more realistic results for heat release through clothing in comparison to other devices. Many researchers have explored the heat and mass transfer properties of clothing and the different aspects of clothing that affect these properties by using the sweating thermal manikin. Chen et al.¹¹ examined the impact of garment fit on the thermal insulation and moisture vapor resistance properties of jackets. They found that thermal insulation and vapor resistance were affected by air gaps and decreased at a specific air gap thickness. An investigation of the effect of T-shirt designs on thermal comfort was carried out by Ho et al.¹³ They indicated that thermal insulation and water vapor resistance are affected by the positions of openings and ventilation panels. Richards et al.³¹ investigated the dry and wet heat loss of two-layer garment combinations and determined the impact of clothing properties on heat transfer through combinations. The combinations with impermeable outerwear had slightly higher dry heat loss and lower apparent evaporative heat loss than those with permeable outerwear. Furthermore, the increase in heat loss occurring from sweating was more pronounced in synthetic underwear as compared to cotton underwear. Wang et al.¹⁵ determined the effects of moisture content and garment fit on the wet thermal insulation of garment combinations, which consisted of underwear and a coverall. The moisture content had a greater impact on the wet thermal insulation of the combinations than the garment fit.

To date, only a few systematic studies have been conducted using a sweating thermal manikin to consider the properties of fabric and garment combinations on the environmental heat exchange of office clothing.^35–38 Therefore, the main aim of this study was to determine the interactions of the fabric and garment properties that influence the heat transfer properties of garment combinations in relation to different upper body parts of the sweating thermal manikin. In this study, garment combinations worn by office workers were used. These combinations consisted of shirts with different weave types and raw materials and regular- and tight-fitting undershirts made out of cotton and polyester. The findings will enable garment designers to understand better the fabric and garment properties and their interactions in order to develop office clothing with increased general and local thermal comfort.

Materials and methods

Materials

Four regular-fitting, long-sleeved shirts made from cotton twill, bamboo twill, cotton/polyester twill, and cotton/polyester plain woven fabrics were included in this study. Undershirts (round neck, sleeveless) made of cotton and polyester single jersey knitted fabrics were manufactured as regular- and tight-fitting by decreasing the size of the undershirts at the girths.³² The physical and structural properties of the fabrics used in the study were characterized according to the related standards for yarn densities (ISO 4921:2000³⁹; ISO 4602:2010⁴⁰), fabric thickness (ISO 5084:1996⁴¹), mass per unit area (ISO 3801:1977⁴²), drape coefficient (ISO 9073-9: 2008⁴³), and air permeability (ISO 9237: 1995⁴⁴), all of which are given in Table 1.

Table 1.

Physical properties of the fabrics. Data are shown as mean values (standard deviation)

SHIRT
Raw material		Weave type	Warp density (ends/cm)	Weft density (picks/cm)	Mass per unit area (g/m²)	Fabric thickness (mm)	Drape coefficient (%)	Air permeability (l/m²/s)
Warp	Weft	Weave type	Warp density (ends/cm)	Weft density (picks/cm)	Mass per unit area (g/m²)	Fabric thickness (mm)	Drape coefficient (%)	Air permeability (l/m²/s)
Cotton	Cotton	3/1 Twill	50.40 (0.52)	37.80 (0.42)	139.29 (1.14)	0.29 (0.01)	36.47 (3.01)	242.70 (7.48)
Bamboo	Bamboo	3/1 Twill	51.10 (0.74)	37.20 (0.63)	142.51 (1.32)	0.30 (0.02)	25.93 (0.10)	122.60 (4.09)
Cotton	Polyester	3/1 Twill	49.70 (0.67)	36.00 (0.47)	142.54 (0.50)	0.30 (0.01)	50.73 (0.22)	310.80 (15.82)
Cotton	Polyester	Plain	49.20 (0.42)	29.10 (0.32)	130.70 (0.87)	0.26 (0.00)	62.56 (0.74)	251.10 (6.97)
UNDERSHIRT
Raw material		Knitted structure	Wale density (wales/cm)	Course density (courses/cm)	Mass per unit area (g/m²)	Fabric thickness (mm)	Drape coefficient (%)	Air permeability (l/m²/s)
Cotton		Single jersey	22.40 (0.52)	16.50 (0.53)	159.36 (2.00)	0.61 (0.01)	24.78 (2.40)	554.30 (17.76)
Polyester		Single jersey	24.90 (0.32)	17.00 (0.82)	187.88 (2.13)	0.69 (0.02)	8.15 (0.86)	741.80 (24.02)

All the garments were manufactured considering the body dimensions of the sweating thermal manikin measured in accordance with ISO 8559:1989.⁴⁵ The circumferences of the sweating thermal manikin and garments were compared, and the ease allowances in the chest and waist were determined as the girth between the body and the garment. Table 2 provides the technical illustrations, the ease allowance of the garments, and the estimated air gap thickness (AGT) and contact area (CA) values between the garments and the skin. To cover all body parts, the lower body and legs of the manikin were dressed in commercial trousers produced from 100% cotton woven fabric.

Table 2.

The sketches of garments, the ease allowance at chest and waist, and the air gap thickness (AGT) and contact area (CA) between garments and the skin

Garment (Fit*)	Shirt (Regular-fitting)	Undershirt (Regular-fitting)	Undershirt (Tight-fitting)
Technical design

Ease allowance (cm)	Shirt–Skin		Undershirt –Skin		Undershirt–Skin
Chest	8		−6		−10
Waist	30		20		4
Body parts	AGT (mm)**	CA (%)	AGT (mm)	CA (%)	AGT (mm)	CA (%)
Chest	10.2	23.5	7.3	32.8	2.9	39.0
Back	16.7	24.6	13.9	30.0	7.1	34.1

*Garment fits were determined following the study of Frackiewicz-Kaczmarek et al.³²

**AGT and CA were predicted from regression models established in the study of Psikuta et al.⁴⁶

A total of 16 different undershirt–shirt combinations were investigated to determine the effect of the weave type and raw material of shirt fabrics on body heat dissipation as well as the effect of the fit and raw material of the undershirts. Two batches of combinations were defined in order to analyze the effects of the fabric and garment properties accurately. In the first group, the combined impacts of the shirt weave type, undershirt raw material, and undershirt fit were investigated. The combined effects of the undershirt and shirt raw materials and the undershirt fit were evaluated in the second group (Table 3).

Table 3.

The undershirt–shirt combinations used in the study

Undershirt		Shirt
Raw material	Garment fit	Raw material	Weave type
1st Group
Polyester	Regular	Cotton/Polyester	3/1 Twill
Cotton	Regular
Polyester	Tight
Cotton	Tight
Polyester	Regular		Plain
Cotton	Regular
Polyester	Tight
Cotton	Tight
2nd Group
Polyester	Tight	Cotton	3/1 Twill
		Cotton/Polyester
		Bamboo
Cotton	Tight	Cotton
		Cotton/Polyester
		Bamboo
Polyester	Regular	Cotton
		Cotton/Polyester
		Bamboo
Cotton	Regular	Cotton
		Cotton/Polyester
		Bamboo

Methodology

The dry heat loss and the evaporative cooling of the garment combinations were measured using an anatomically shaped sweating thermal manikin, which had the body dimensions of an average male adult. The climatic chamber was set at 20℃ (±1℃) with 50% (±5%) relative humidity, and 0.15 ms⁻¹ (±0.1 ms⁻¹) air speed. The garments were acclimatized in the climatic chamber for 24 hours prior to all tests.

The measurements were taken in three phases: the acclimatization phase, sudatory exposure phase, and recovery phase. Each phase was set to a 60-minute duration. The manikin surface temperature was maintained at 34℃ (±0.01℃) for all phases. During the sudatory exposure phase, distilled water was supplied to sweat outlets using hydrostatic pressure as a driving force. The total sweating area of the upper body of the manikin was 0.51 m², and the sweating rate was determined as 176.5 g/m²/h. The sweating rate reflects low to moderate activity for office workers. All experiments were repeated three times, and the surface temperature, power, and weight of the manikin were recorded every minute throughout the measurement.

For a homogeneous distribution of the perspired water on the manikin's surface, the lower and upper body parts were clothed with a knitted fabric (VENOSAN®4000) simulating human skin. The manikin was then dressed in the undershirt, shirt, and trousers (Figure 1). The shirt cuffs were fastened and the trunk at neck level kept open taking into account the findings of Ismail et al.⁴⁷ During the tests, the shirt was tucked into the trousers, and the position of the shirt tail was kept constant in each test so as not to affect the size and shape of the air gaps. Dry thermal resistance and evaporative heat loss were calculated for the upper body, which includes the chest, back, and arms of the manikin. These calculations were also made for the trunk of the manikin, which consists of its chest and back only (Figure 1).

Figure 1.

The sweating thermal manikin and the garments used in the study.

The total clothing thermal resistance was calculated according to the parallel model – surface area averaged thermal insulation (ISO 15831: 2004⁴⁸);

\begin{matrix} I_{t} = \frac{[(\sum_{i} f_{i} \times T_{si}) - T_{a}] \times A}{\sum_{i} H_{ci}} \end{matrix}

(1)

\begin{matrix} I_{cl} = I_{t} - \frac{I_{a}}{f_{cl}} \end{matrix}

(2)

\begin{matrix} H L_{ev} = H L_{wet} - H L_{dry} (W / m^{2} \end{matrix})

(3)

where I_t is the total thermal insulation of the clothing ensemble for the stationary manikin (m²K/W); f_i is the area factor of section i of the nude manikin; T_si is the local surface temperature of section i of the manikin (℃); T_a is the air temperature within the testing chamber (℃); H_ci is the local heat loss from section i of the manikin (W); I_cl is the basic thermal insulation of the clothing ensemble with the manikin stationary (m²K/W); I_a is the total thermal insulation of the boundary air layer measured on the nude stationary manikin (m²K/W); f_cl is the clothing area factor. The f_cl of the manikin's skin was assumed to be 1, and when the manikin was dressed with the shirt, f_cl was 1.11 and 1.17 for the trunk and the upper body of the manikin, respectively.^28,49 The evaporative heat loss (HL_ev) was obtained by subtracting the heat loss from the manikin with dry clothing (HL_dry) from the heat loss from the manikin during sweating (HL_wet).

The results were evaluated with the univariate analysis of variance (ANOVA) using SPSS version 22.0 statistical package program (IBM, Armonk, NY, USA), and p < 0.05 was considered to be significant for all statistical analyses. However, when the group variances were not statistically equal, the Brown-Forsythe ANOVA test was performed. In addition, the statistical effect size (eta squared, η², for the one-way ANOVA; partial eta squared, $η_{partial}^{2}$ , for the univariate analysis of variance)⁵⁰ of the factors, which have significant differences in the dry thermal resistance and the evaporative heat loss measured from the garment combinations, was also calculated. The statistical effect size is described as the strength of the relationship between the dependent and independent variables and/or the magnitude of the difference between the levels of the independent variables according to the dependent variable.⁵¹ According to Cohen's criteria, the statistical effect size is large when the independent variable accounts for 14% of the variability in a dependent variable (η² = 0.14)⁵²; the factors having only strong effects were examined in this study.

Results

The dry thermal resistance and evaporative heat loss from the different manikin body segments of interest (i.e., upper body, trunk, chest, and back) were examined in this study. The graphs below (figures 2–5) show the measured properties for the upper body (on the right) and trunk (on the left) of the manikin. Because the undershirt did not cover the arms of the manikin, the data for the trunk of the manikin is more salient in explaining the factors that affect heat exchange. The results of the dry thermal resistance and evaporative heat loss calculated for the chest and back of the manikin are given in Appendix 1.

Figure 2.

Dry thermal resistance of garment combinations including different shirt weave types, undershirt raw materials, and undershirt fits for (a) the upper body and (b) the trunk of the manikin. Data are shown as mean values with error bars indicating 1 standard error.

Effects of the shirt weave type and the undershirt raw material and fit

Dry thermal resistance

Figures 2a and 2b present the dry thermal resistance of the undershirt–shirt combinations, which includes different shirt weave types, undershirt raw materials, and undershirt fits, measured for the upper body and trunk of the manikin. As these figures indicate, similar trends were observed for the dry thermal resistances measured from the trunk and upper body of the manikin. The dry thermal resistance of garment combinations with twill shirts was slightly higher than that with plain shirt fabrics. In addition, the dry thermal resistance in the trunk increased by approximately 6–8% in the combinations with the regular-fitting undershirts when compared to the tight undershirts. A slight difference between the dry thermal resistance of garment combinations with the polyester and the cotton undershirts was observed. The garment combinations including the polyester undershirt revealed greater thermal resistance than those with the cotton undershirt.

Statistical analyses were performed to determine the factors influencing the dry thermal resistance of garment combinations for the upper body, trunk, chest, and back of the manikin (Table 4). The fit of undershirt had a significant effect on the dry thermal resistance values, which was calculated for all body regions. The weave type of shirt showed a statistically significant difference in the dry thermal resistance of the upper body and back of the manikin. In these body parts, the statistical effect size of weave type (

η_{partial}^{2}

) on the dry thermal resistance was lower than that of the undershirt fit. However, there was no effect of the raw material of undershirt on the dry thermal resistance of garment combinations used in the study (p < 0.05).

Table 4.

Statistically significant differences among the dry thermal resistance of garment combinations in terms of shirt weave type, undershirt raw material, and undershirt fit

Upper body	F	p	$η_{partia l^{*}}^{2}$
Weave type (Shirt)	4.547	.049	.221
Fit (Undershirt)	14.727	.001	.479
Trunk	F	p	$η_{partia l^{*}}^{2}$
Fit (Undershirt)	40.213	.000	.715
Chest	F	p	η²*
Fit (Undershirt)	23.099	.000	.512
Back	F	p	$η_{partia l^{*}}^{2}$
Weave type (Shirt)	5.692	.030	.262
Fit (Undershirt)	18.567	.001	.537

*η² and $η_{partial}^{2}$ show the statistical effect size of factors examined.

Evaporative heat loss

Figures 3a and 3b show the evaporative heat losses measured from the upper body and trunk of the manikin for the garment combinations, which include two shirt weave types (3/1 twill, plain), two undershirt raw materials (cotton, polyester) and two undershirt fits (regular, tight). It was observed that the combinations with the polyester undershirt had generally higher evaporative heat losses than those with the cotton undershirt in both the upper body and the trunk. Conversely, the garment combination of the twill shirt and the polyester regular-fitting undershirt had a lower value than the combination consisting of the twill shirt and the cotton regular-fitting undershirt. The differences between the cotton and polyester undershirts were statistically significant for the garment combinations using tight-fitting undershirts (p < 0.05). On the other hand, the differences between the evaporative heat loss of combinations with the polyester and cotton regular-fitting undershirts were insignificant (p < 0.05) (Figure 3b).

Figure 3.

Evaporative heat losses from garment combinations including different shirt weave types, undershirt raw materials, and undershirt fits for (a) the upper body and (b) the trunk of the manikin. Data are shown as mean values with error bars indicating 1 standard error.

The statistical analyses showed that the interaction of shirt weave type, undershirt fit, and undershirt raw material had a significant effect on the evaporative heat loss from the upper body (Table 5). However, the effects of the undershirt properties alone (raw material and garment fit) were significant for the evaporative heat loss of the trunk. Examining the effects of related factors on the evaporative heat loss in the chest and back of the manikin separately (Table 5), the evaporative heat loss from the chest was found to be related to the raw material of the undershirts. The fit of the undershirt was more important for the evaporative heat loss from the back of the manikin (p < 0.05).

Table 5.

Statistically significant differences among the evaporative heat losses from the garment combinations in terms of shirt weave type, undershirt raw material, and undershirt fit

Upper body	F	P	$η_{partia l^{*}}^{2}$
Raw material (Undershirt)	9.348	.008	.369
Weave type (Shirt) * Raw material (Undershirt)	5.034	.039	.239
Weave type (Shirt) * Raw material (Undershirt) * Fit (Undershirt)	3.930	.065	.197
Trunk
Raw material (Undershirt)	8.158	.011	.338
Fit (Undershirt)	4.822	.043	.232
Raw material (Undershirt)*Fit (Undershirt)	9.842	.006	.381
Chest
Raw material (Undershirt)	6.992	.018	.304
Back
Fit (Undershirt)	10.805	.005	.403
Raw material (Undershirt)*Fit (Undershirt)	11.900	.003	.427

* $η_{partial}^{2}$ shows the statistical effect size of factors examined.

Effects of the shirt raw material and the undershirt raw material and fit

Dry thermal resistance

Dry thermal resistance values of the garment combinations, which consist of the shirts manufactured from cotton, cotton/polyester, and bamboo woven fabrics and the tight- or regular-fitting undershirts made from cotton and polyester knitted fabrics, were calculated for the upper body and trunk of the manikin, illustrated in figures 4a and 4b. The dry thermal resistance of the combination including the polyester regular-fitting undershirt and the cotton/polyester shirt was the highest of all combinations for both the upper body and trunk of the manikin. It can be seen from figures 4a and 4b that the dry thermal resistance of the regular-fitting polyester undershirt was slightly higher compared with the tight-fitting polyester undershirt. However, no similar tendency was observed in the combinations of the cotton undershirt with either the cotton or the bamboo shirts. When the regular and tight cotton undershirts were used in these combinations, the dry thermal resistance values were almost identical.

Figure 4.

Dry thermal resistance of garment combinations including different shirt raw materials, undershirt raw materials, and undershirt fits for (a) the upper body and (b) the trunk of the manikin. Data are shown as mean values with error bars indicating 1 standard error.

Figure 5.

The evaporative heat loss from the garment combinations including different shirt raw materials, undershirt raw materials and undershirt fits for (a) the upper body and (b) the trunk of the manikin. Data are shown as mean values with error bars indicating 1 standard error.

Statistical analyses demonstrated that the raw material of the shirt, the fit of the undershirt, and the interaction of these factors had significant effects on the dry thermal resistance of garment combinations measured for both the upper body and trunk of the manikin (Table 6).

Table 6.

Statistically significant differences among the dry thermal resistance of garment combinations in terms of shirt raw material, undershirt raw material, and undershirt fit

Upper body	F	p	$η_{partia l^{*}}^{2}$
Raw material (Shirt)	14.138	.000	.541
Fit (Undershirt)	6.755	.016	.220
Raw material (Shirt) * Fit (Undershirt)	3.853	.035	.243
Trunk
Raw material (Shirt)	9.340	.001	.438
Fit (Undershirt)	19.807	.000	.452
Raw material (Shirt) * Fit (Undershirt)	9.156	.001	.433
Chest
Fit (Undershirt)	14.672	.001	.379
Raw material (Shirt) * Fit (Undershirt)	6.160	.007	.339
Back
Raw material (Shirt)	7.983	.002	.399
Fit (Undershirt)	5.779	.024	.194
Raw material (Shirt) * Fit (Undershirt)	4.053	.030	.252

* $η_{partial}^{2}$ shows the statistical effect size of factors examined.

As seen in Table 6, while the factor having the greatest effect on the upper body was the raw material of the shirt ( $η_{partial}^{2}$ : 0.541), all factors affecting dry thermal resistance at the trunk had similar statistical effect sizes. Examining the chest and back segments of the manikin separately (Table 6), it was determined that the fit of undershirt was a more important factor for the chest, whilst the dry thermal resistance calculated for the back of the manikin was largely affected by the raw material of the shirt. Furthermore, the dry thermal resistance of garment combinations was not associated with the raw material of the undershirts used in the study (p < 0.05).

Evaporative heat loss

Figures 5a and 5b illustrate the evaporative heat losses measured from the upper body and trunk of the manikin dressed with the garment combinations, which consist of the cotton, cotton/polyester, and bamboo shirts and the regular- and the tight-fitting undershirts manufactured from cotton and polyester fabrics. The results indicate that when examining the garment combinations of tight-fitting undershirts, the combinations with polyester undershirts had higher evaporative heat losses than those with cotton undershirts. However, there was no similar tendency for the combinations of regular-fitting undershirts.

According to the ANOVA results performed to evaluate the effects of the raw materials of the shirt and undershirt fabrics on the evaporative heat loss of garment combinations with regular-fitting undershirts, the raw materials of the undershirt and the shirt did not show any significant effect (p < 0.05). As can be seen in Table 7, the effect of the undershirt fit on evaporative heat loss was more significant for the back of the manikin (p < 0.05). On the other hand, evaporative heat loss from the chest was associated with the raw material of the undershirt. Furthermore, the raw material of the shirt was significant for evaporative heat loss from the upper body and trunk of the manikin (p < 0.05).

Table 7.

Statistical significant differences among the evaporative heat loss from the garment combinations in terms of shirt raw material, undershirt raw material, and undershirt fit

Upper body	F	P	$η_{partial}^{2} *$
Raw material (Shirt) * Fit (Undershirt)	5.205	.013	.303
Raw material (Shirt) * Raw material (Undershirt) * Fit (Undershirt)	4.065	.030	.253
Trunk
Raw material (Undershirt)	7.102	.014	.228
Raw material (Shirt) * Raw material (Undershirt) * Fit (Undershirt)	2.256	.127	.158
Chest
Raw material (Undershirt)	5.790	.024	.194
Back	F	P	$η^{2} *$
Fit (Undershirt)	5.838	.021	.147

*η² and $η_{partial}^{2}$ show the statistical effect size of factors examined.

Appendix 1.

The dry thermal resistance and the evaporative heat loss through the garment combinations for the chest and the back of the manikin. Data are shown as mean (standard deviation)

Undershirt		Shirt		Dry thermal resistance (m²K/W)		Evaporative heat loss (W/m²)
Raw material	Garment fit	Raw material	Weave type	Chest	Back	Chest	Back
Polyester	Regular	Cotton/Polyester	3/1 Twill	0.264 (0.005)	0.377 (0.016)	26.576 (5.607)	11.554 (1.164)
Cotton	Regular			0.257 (0.004)	0.374 (0.020)	26.216 (2.100)	15.458 (2.431)
Polyester	Tight			0.245 (0.002)	0.348 (0.017)	29.878 (3.043)	18.467 (2.445)
Cotton	Tight			0.242 (0.007)	0.345 (0.004)	24.369 (2.710)	13.740 (1.756)
Polyester	Regular		Plain	0.259 (0.012)	0.361 (0.029)	26.781 (3.005)	15.248 (3.704)
Cotton	Regular			0.258 (0.003)	0.357 (0.010)	25.300 (1.860)	14.142 (2.895)
Polyester	Tight			0.250 (0.013)	0.329 (0.005)	29.718 (2.389)	21.743 (0.551)
Cotton	Tight			0.245 (0.005)	0.333 (0.012)	23.925 (1.866)	15.537 (2.968)
Polyester	Tight	Cotton	3/1 Twill	0.245 (0.005)	0.337 (0.000)	27.743 (1.955)	19.055 (2.274)
		Cotton/Polyester		0.245 (0.002)	0.348 (0.017)	29.878 (3.043)	18.467 (2.445)
		Bamboo		0.248 (0.003)	0.342 (0.016)	27.057 (1.540)	15.824 (1.198)
Cotton		Cotton		0.251 (0.010)	0.333 (0.015)	25.832 (0.918)	14.213 (0.673)
		Cotton/Polyester		0.242 (0.007)	0.345 (0.004)	24.369 (2.710)	13.740 (1.756)
		Bamboo		0.241 (0.011)	0.359 (0.013)	26.414 (2.531)	14.178 (1.078)
Polyester	Regular	Cotton		0.250 (0.006)	0.348 (0.012)	26.758 (3.342)	14.045 (5.067)
		Cotton/Polyester		0.264 (0.005)	0.377 (0.016)	26.576 (5.607)	11.554 (1.164)
		Bamboo		0.253 (0.002)	0.354 (0.012)	29.384 (2.910)	14.004 (4.492)
Cotton		Cotton		0.246 (0.006)	0.335 (0.010)	24.089 (0.813)	11.339 (1.076)
		Cotton/Polyester		0.257 (0.004)	0.374 (0.020)	26.216 (2.100)	15.458 (2.431)
		Bamboo		0.248 (0.006)	0.342 (0.018)	26.365 (4.121)	14.789 (3.850)

Discussion

Thermal comfort is largely related to changes in temperature and moisture on the skin, and the overall thermal sensation is affected by local thermal sensations of the different body regions, particularly the chest and back.⁵³ The findings of this study showed clearly the combined effects of the fabric properties (raw material and weave type) and garment properties (garment fit) of the undershirt and shirt layers on the dry thermal resistance and evaporative heat loss measured from different upper body regions.

In this study, a small difference between the dry thermal resistances of the garment combinations including the regular- and the tight-fitting undershirts was observed. The dry thermal resistance of the combinations with regular-fitting undershirts was generally about 6–8% higher than those with tight-fitting undershirts (Figure 2b). This might be related to the lower AGT values calculated in the tight-fitting undershirts (Table 2). On the other hand, while the difference between regular- and tight-fitting polyester undershirts combined with the cotton or bamboo shirts dropped to 1–2%, there was no difference between the dry thermal resistances of the regular- and tight-fitting cotton undershirts, which were combined with the cotton or bamboo shirts (Figure 4b). These observations might be explained by the drape behavior of the garment layers. When the second layer with a high drape coefficient (i.e., cotton/polyester shirt with a low propensity to drape) was used in the garment combinations, the effect of the undershirt fit on the dry thermal resistance was observed (Table 4). The stiffer fabric might create larger air gaps on the regular-fitting undershirt since the folds of the regular-fitting undershirt acted as a kind of cantilever. On the other hand, when the second layer was produced from the fabrics with a lower drape coefficient (i.e., bamboo or cotton shirt), this layer may have collapsed onto the first layer, particularly on the regular-fitting undershirt. Finally, this might lead to no or a very small difference between the dry thermal resistances of the garment combinations with the regular- and tight-fitting undershirts.

This study demonstrated that both the raw material of the shirt and the fit of the undershirt have a significant effect on the dry thermal resistance of the upper body and the trunk and, thus, should be considered when manufacturing comfortable office wear (Table 6). Moreover, examining the crucial factors in relation to the chest and back of the manikin, it was observed that the dry thermal resistance of the back region depended on the shirt properties, whilst the chest was not directly affected by them (tables 4 and 6). This finding might be due to the body shape of the manikin. While the back of the manikin has a largely concave form, the chest is a convex body region. Accordingly, the back region has a higher AGT than the chest of the manikin (Table 2). Hence, the variability in the dry thermal resistance of the back region with a change in outer layer properties might be more apparent owing to the large air gaps in comparison with the chest region of the manikin.

Shirt fabric properties had statistically significant effects on both the dry thermal resistance (tables 4 and 6) and the evaporative heat loss of the upper body of the manikin (tables 5 and 7). This might be due to the fact that the arms of the manikin were covered with the shirt fabric only. On the other hand, only undershirt properties influenced the evaporative heat loss from the trunk (tables 5 and 7). When the produced sweat is wicked away from the skin before evaporating and is absorbed by the undershirt, the cooling efficiency decreases.^26,27,54 Thus, the undershirts made out of the fabric with the good absorption and transfer properties (i.e., cotton) had lower evaporative heat loss than those made of hydrophobic fibers (i.e., polyester) (figures 3b and 5b).

Tight-fitting undershirts have a higher CA where the sweat can be distributed evenly over a larger area^26,28 and thus, it is expected that they would have more evaporative heat loss than regular-fitting undershirts (Table 2). In this study, the difference between the evaporative heat losses of the tight- and regular-fitting undershirts was more apparent for the garment combinations with the polyester undershirts than those with the cotton undershirts (Figure 3b). This can be explained by the better drapability (lower drape coefficient) and wickability properties of the polyester undershirts. Fabric drapability influences the AGT and the CA between the skin and the garment,³² and as the drape coefficient of the fabric decreases, the CA in the clothing increases. There was no significant difference between the evaporative heat losses measured for the combinations of the regular- or tight-fitting undershirts and the bamboo shirt (Figure 5b). This might arise from the high water absorption capacity of the bamboo fibers used in the shirt.^35,55 Moreover, the bamboo shirt layer, which has a lower drape coefficient, may collapse onto the undershirt layer and thereby, might eliminate the difference between the regular- and tight-fitting undershirts.

In considering the evaporative heat loss from the back and chest regions, the undershirt fit was revealed to have a significant impact on the back region. On the other hand, the evaporative heat loss from the chest was strongly dependent on the raw material of the undershirt (tables 5 and 7). In the chest region, the effect of the undershirt fit on evaporative heat loss may not be observed due to the smaller air gaps and the larger CA between the skin and the undershirt.^28,32 Furthemore, higher evaporative heat loss in the chest compared with the back of the manikin might point to the impact of the air gaps between the layers on evaporative heat loss (Appendix 1).

Conclusions

In this study, the effects of fabric properties (weave type, raw material) and garment fit on the heat transfer behavior of garment combinations (undershirt and shirt) were investigated using a sweating thermal manikin. This study revealed that the dry thermal resistance of the combinations was mainly affected by the undershirt fit and the raw material of the shirt because of their effect on the air layers between the skin and clothing. In addition, the evaporative heat losses from the garment combinations were influenced by the undershirt properties (raw material, garment fit). Furthermore, the magnitude of the effects varied over different body regions. The impact of the undershirt fit on the evaporative heat loss in the back region of the manikin was found to be higher than that in the chest region. The raw material of the undershirt was the primary factor in the difference in evaporative heat loss measured at the chest. Whilst the dry thermal resistance at the back was associated with the raw material of the shirt, the dry thermal resistance at the chest was mostly dependent on the fit of the undershirt. Moreover, the magnitude of the effect of shirt properties was found to be higher in the upper body because the arms of the manikin were covered with only shirt fabric. The findings of the study contribute to the understanding of the influence of fabric and garment properties on heat exchanges through garments. This knowledge will enable garment designers to improve the thermal comfort of office clothing combinations. Further studies are required to determine the effects of different functional materials, environmental conditions, and body movements on office thermal comfort of various combinations consisting of upper- and lower-body garments.

Footnotes

Acknowledgment

The authors wish to thank Dr Emel Mert for her valuable comments and her assistance in the preparation of the garments.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by The Scientific and Technological Research Council of Turkey (TÜBİTAK) – 2214-A Research Fellowship Program.

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