Human Comfort

Evaluating Comfort and Related Physical Properties of Textiles

28 - 30° C

Human Comfort

Comfort is freedom from pain, freedom from discomfort. It is a neutral state1

Comfort is a pleasant state of physiological, psychological and physical harmony between a human being and the environment2

1 Hatch, K.L. (1993). Textile science. Minneapolis, MN: West Publishing Co., p. 26.

2 Slater, K. (1985). Human comfort. Springfield, IL: Charles C. Thomas Publisher, p. 4.

What Comfort really is:

RelativeSubjective

PsychologicalPhysiological

Thermal-Sensorial-Mobile-

Human ComfortPsychological Comfort implies that

individuals need specific garments, fabrics, colors and design features to help them feel confident and at ease within the context of the various roles they assume.

Factors: Self-Image Relationship with others: Trust, love and

respect Need of privacy: Solitude, silence, anonymity

Human ComfortPhysiological Comfort refers to

maintenance of thermal balance: The proper relationship between body heat production and loss.Factors: Cardiovascular system Skeleto-muscular system Central nervous system Pulmonary system Digestive system Thermoregulatory mechanism

Human ComfortPhysical Aspects of Comfort refer to

different sensations and feelings of discomfort and/or pain, which influence the two types of comfort.

Factors: Touch Sight Hearing Taste Smell

Comfort-Related Physical Properties of Textiles

Thermo-physiological Comfort Thermal resistance Water vapor permeability (breathability) Wickability Sorption of water Water resistance, repellency and proofness Drying rate

Sensorial (Neuro-physiological) Comfort Prickliness, itchiness, inflammation Roughness Thermal character (warm/cool feeling) Electrostatic propensity

Body-Movement Comfort Stretch Weight Pressure/compression

Physical Characteristics of Textile Materials Influencing Thermal Comfort

Fabric MassFabric ThicknessFiber, Yarn, and Fabric StructuresPorosity is the ratio of air space to the total

volume of the fabric, expressed as a percentage

Cover Factor is defined as the opacity or hiding power in textiles

The Physics of Human Comfort

Body metabolism Heat transferEvaporation

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Comfort Model

Body Thermal Balance

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Body Thermal Balance

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21

Heat Transfer

Heat Transfer refers to the transfer of heat energy from one environment to another. Heat transfer occurs whenever a temperature difference (T) exists between two environments; heat moves from the warmer surface or area to the cooler surface or area.

The rate at which heat is transferred depends on T as well as any resistance imposed between the two environments.

Modes of Heat Transfer Conduction: is the transfer of heat by physical

contact, either within a body or between two touching bodies

Convection: is heat transfer via a moving air mass within space

Radiation: involves heat transfer through space in the form of electromagnetic energy

Heat Transfer

Units. Several terms are used to quantify heat transfer: Thermal transmittance (U): is the rate of heat transfer

per unit area, U = W/m2K°. Thermal conductance ©: is defined by the same

formula, C = W/m2K° Thermal resistance (r): the rate of flow of heat

through a fabric under standard conditions. The r-value is the inverse of thermal transmittance (r = 1/U).

A fabric has a thermal resistance of one “tog” when a temperature difference between two surfaces of 0.1°C produces a heat flow equal to 1 W/m2.

A “clo” is the resistance necessary to keep a resting person (producing heat at a rate of 58 W/m2) comfortable at 21°C and at an air movement rate of 0.1 m/s.

1 clo = 1.55 togs; 1 clo = 0.1548r; 1 clo = U/0.1548

Effect of Fabric Properties on Heat Transfer Fiber type and structure Yarn type and structure Fabric type and structure Finishes applied

Heat Transfer

Heat Transfer

Standard Test Methods CAN/CGSB-4.2 No. 70.1 – 94, Thermal

insulation performance of textile materials ASTM D 1518 – 85, Thermal transmittance of

textile materials

Thermal Insulation

cold plate

hot plate

specimenProcedure 1

cold platespecimen

hot plate

Procedure 2

cold plate

cold platespecimen

specimenhot plate Guarded Hot Plate

Thermal CharacterThermal absorptivity (b) is a transient-state

parameter that describes the thermal contact properties of a textile material (warm-cool feeling) at the beginning (first two seconds) of its contact with human skin.

Where: = thermal conductivity

c = thermal capacity

The lower the value of (b), the warmer the feeling

b = (c)1/2 [Ws1/2/m2K]

Alambeta: measurement of

transient and steady-state

thermo-physical properties

Moisture TransferIt refers to the transfer of liquid water or vapor.

The transfer of moisture generally is from the wetter environment to the drier environment until equilibrium is reached. Moisture is produced by the body in the form of perspiration (insensible and sensible perspirations).

Types of Moisture Transfer Diffusion Sorption Wicking Evaporation

Water-Proof FabricOUTER

INNER

Breathable Fabric

water vapour

Liquid water

Moisture Transfer

Factors Affecting Moisture Transfer Fiber type and structure Yarn type and structure Fabric type and structure Finishes applied

Moisture TransferStandard Test Methods

CAN/CGSB-4.2 No. 49 – 99, Resistance of materials to water vapour diffusion

ASTM F1868-98, Thermal and evaporative resistance of clothing materials using a sweating hot plate

ISO 11092: 1993 (E), Measurement of thermal and water-vapour resistance under steady-state conditions (sweating guarded-hotplate test)

ASTM E 96, Water vapor transmission of materials ASTM D 4772, Standard test method for surface

water absorption of terry fabrics (water flow test method)

AATCC Method 79, Absorbency of bleached textiles

WATER VAPOUR

DIFFUSION

Sweating Guarded Hot Plate

Water Resistance and RepellencyWater Resistance: a physical barrier to

water penetrationWater Repellent: does not allow water

penetration in one side but it allows moisture transfer from body

Water-proof: does not allow any penetration of water from either side to the other.

Shower-proof, Rain-proof

AIR

water drop

Hydrophilic

Cotton (attractive surface)

AIRwater drop

Hydrophobic

Olefin (repulsive surface)

Factors Affecting Water Resistance and Repellency Fiber type and structure Yarn type and structure Fabric type and structure Finishes applied

Water Resistance and Repellency

Water Resistance and RepellencyStandard Test Methods

AATCC Method 21, Water repellency: Static absorption test

AATCC Method 22, Water repellency: Spray test AATCC Method 35, Water resistance: rain test AATCC Method 42, Water resistance: Impact

penetration test AATCC Method 70, Water repellency: Tumble jar

dynamic absorption test AATCC Method 127: Water resistance: Hydrostatic

pressure test

Impact penetration tester

Rain tester Hydrostatic pressure tester

Air Permeability

It is the degree to which the material is penetrable by air. It is also the rate of air flow through a fabric when there is a different air pressure on either surface of the fabric.

Air Permeability

Factors Affecting Air Permeability Fiber type and structure Yarn type and structure Fabric type and structure Finishes applied

Standard Test Methods CAN/CGSB-4.2 No. 36 – M89, Air

permeability ASTM D – 737, Air permeability of textile

fabrics