Clothing insulation

Last updated October 29, 2024

Clothing insulation is the thermal insulation provided by clothing.^[1]^[2]

Thermophysiological comfort

Thermophysiological comfort is the capacity of the clothing material that makes the balance of moisture and heat between the body and the environment. It is a property of textile materials that creates ease by maintaining moisture and thermal levels in a human's resting and active states. The selection of textile material significantly affects the comfort of the wearer. Different textile fiber holds individual properties that suit in different environments. Natural fibers are breathable and absorb moisture, while synthetic fibers are hydrophobic; they repel moisture and do not allow air to pass. Different environments demand a diverse selection of clothing materials. Hence the appropriate choice is important.^[3]^[4]^[5]^[6]^[7]^[8]^[9] The major determinants that influence Thermophysiological comfort are the permeable construction, heat, and moisture transfer rate.^[10]

Mechanisms of insulation

There are three kinds of heat transfer: conduction (exchange of heat through contact), convection (movement of fluids), and radiation.

Air has a low thermal conductivity but is very mobile. There are thus two elements that are important in protecting from the cold::

setting up a layer of still air which serves as insulation, by the use of fibres (wool, fur, et cetera)
stopping the wind from penetrating and replacing the layer of warm air close to the body

Another important factor is humidity. Water is a better conductor of heat than air, thus if clothes are damp — because of sweat, rain, or immersion — water replaces some or all of the air between the fibres of the clothing, causing thermal loss through conduction and/or evaporation.

Thermal insulation is thus optimal with three layers of clothing:

a layer near the body for hygiene (changed more often than the other clothing), whose role is to get rid of sweat so it does not remain in contact with the skin;
an outer close-knit or closely woven layer as a wind breaker, usually thin — if there is a risk of precipitation this should be impermeable, the ideal being a textile that stops water droplets but allows water vapor to pass so as to remove evaporated sweat (a textile of this sort is said to "breathe");
and between the two, a "thick" layer that traps the air and prevents contact between the skin and the wind-breaking layer (which, as it is thin, gets close to the ambient temperature).

The layers of trapped air between the skin and the exterior surface play a major insulating role. If the clothing is squeezed tight (as by the straps of a backpack), insulation will be poorer in those places. Insulation is improved when convection in the air layers is minimised.

Units and measurement

Clothing insulation may be expressed in clo units.^[11] The clo has the same dimensions as the R value (square metre kelvins per watt or m²⋅K/W) used to describe insulation used in residential and commercial construction—thus, the higher the value, the better the insulation performance.

1 clo = 0.155 K·m²·W⁻¹ ≈ 0.88 K·m²·BTU·W⁻¹·ft ⁻²·°F ⁻¹·hr ⁻¹ R. One clo is the amount of insulation that allows a person at rest to maintain thermal equilibrium in an environment at 21°C (70°F) in a normally ventilated room (0.1 m/s air movement).

There are a number of ways to determine clothing insulation provided by clothes, but the most accurate according to ASHRAE Fundamentals are measurements on heated manikins and on active subjects. Equations may then be used to calculate the thermal insulation. Because clothing insulation cannot be measured for most routine engineering applications, tables of measured values for various clothing ensembles can be used.^[11] According to ASHRAE-55 2010 standard, there are three methods for estimating clothing insulation using the tables provided.

If the ensemble in question matches reasonably well with one on Table 1, the indicated value of intrinsic clothing insulation can be used;
It is acceptable to add or subtract garments on Table 2 from the ensembles in Table 1 to estimate the insulation of ensembles that differ in garment composition;
It is possible to define a complete clothing ensemble as a combination of individual garments using Table 2.^[1]

Another unit that is used is the " tog ":

1 tog = 0.1 K·m²·W⁻¹ ≈ 0.645 clo

1 clo = 1.55 togs

The name comes from the word "togs", British slang for clothes.^[12]

Clothing ensembles and garments

Table 1 – Typical insulation for clothing ensembles^[11]
Ensemble description	I_cl (clo)
Walking shorts, short-sleeved shirt	0.36
Trousers, short-sleeved shirt	0.57
Trousers, long-sleeved shirt	0.61
Same as above, plus suit jacket	0.96
Same as above, plus vest and T-shirt	0.96
Trousers, long-sleeved shirt, long-sleeved sweater, T-shirt	1.01
Same as above, plus suit jacket and long underwear bottoms	1.30
Sweat pants, sweat shirt	0.74
Long-sleeved pajama top, long pajama trousers, short 3/4 sleeved robe, slippers (no socks)	0.96
Knee-length skirt, short-sleeved shirt, panty hose, sandals	0.54
Knee-length skirt, long-sleeved shirt, full slip, panty hose	0.67
Knee-length skirt, long-sleeved shirt, half slip, panty hose, long-sleeved sweater	1.10
Knee-length skirt, long-sleeved shirt, half slip, panty hose, suit jacket	1.04
Ankle-length skirt, long-sleeved shirt, suit jacket, panty hose	1.10
Long-sleeved coveralls, T-shirt	0.72
Overalls, long-sleeved shirt, T-shirt	0.89
Insulated coveralls, long-sleeved thermal underwear, long underwear bottoms	1.37

Table 2 – Garment insulation^[11]
Garment description	I_cl (clo)	Garment description	I_cl (clo)
Underwear		Dresses and skirts
Bra	0.01	Skirt (thin)	0.14
Panties	0.03	Skirt (thick)	0.23
Men's briefs	0.04	Sleeveless, scoop neck (thin)	0.23
T-shirt	0.08	Sleeveless, scoop neck (thick), i.e., jumper	0.27
Half-slip	0.14	Short-sleeve shirtdress (thin)	0.29
Long underwear bottoms	0.15	Long-sleeve shirtdress (thin)	0.33
Full slip	0.16	Long-sleeve shirtdress (thick)	0.47
Long underwear top	0.20
Footwear		Sweaters
Ankle-length athletic socks	0.02	Sleeveless vest (thin)	0.13
Pantyhose/stockings	0.02	Sleeveless vest (thick)	0.22
Sandals/thongs	0.02	Long-sleeve (thin)	0.25
Shoes	0.02	Long-sleeve (thick)	0.36
Slippers (quilted, pile lined)	0.03
Calf-length socks	0.03	Suit jackets and waistcoasts (lined)
Knee socks (thick)	0.06	Sleeveless vest (thin)	0.10
Boots	0.10	Sleeveless vest (thick)	0.17
Shirts and blouses		Single-breasted (thin)	0.36
Sleeveless/scoop-neck blouse	0.12	Single-breasted (thick)	0.44
Short-sleeve knit sport shirt	0.17	Double-breasted (thin)	0.42
Short-sleeve dress shirt	0.19	Double-breasted (thick)	0.48
Long-sleeve dress shirt	0.25
Long-sleeve flannel shirt	0.34	Sleepwear and Robes
Long-sleeve sweatshirt	0.34	Sleeveless short gown (thin)	0.18
Trousers and coveralls		Sleeveless long gown (thin)	0.20
Short shorts	0.06	Short-sleeve hospital gown	0.31
Walking shorts	0.08	Short-sleeve short robe (thin)	0.34
Straight trousers (thin)	0.15	Short-sleeve pajamas (thin)	0.42
Straight trousers (thick)	0.24	Long-sleeve long gown (thick)	0.46
Sweatpants	0.28	Long-sleeve short wrap robe (thick)	0.48
Overalls	0.30	Long-sleeve pajamas (thick)	0.57
Coveralls	0.49	Long-sleeve long wrap robe (thick)	0.69

Further considerations and examples

Other factors that influence the clothing insulation are posture and activity. Sitting or lying change the thermal insulation due to the compression of air layers in the clothing, but at the same time - depending on the materials that are made of - chairs and bedding can provide considerable insulation. While it is possible to determine the increase of insulation provided by chairs, sleeping or resting situations are more difficult to evaluate unless the individual is completely immobile.^[1] Body motion decreases the insulation of a clothing ensemble by pumping air through clothing openings and/or causing air motion within the clothing. This effect varies considerably depending on the nature of the motion and of the clothing. Accurate estimates of clothing insulation for an active person are therefore not available, unless measurements are made for the specific condition (e.g., with a walking manikin). A rough estimate of the clothing insulation for an active person is:

I_{cl, active} = I_cl ×(0.6+0.4/M) 1.2 met < M < 2.0 met

where M is the metabolic rate in met units and I_cl is the insulation without activity. For metabolic rates less than or equal to 1.2 met, no adjustment is recommended.^[1]

Clothing insulation is correlated with outdoor air temperature, indoor operative temperatures, relative humidity and also by the presence of a dress code in the environment in question. Recent studies have developed dynamic predictive clothing insulation models that allow more precise thermal comfort calculation, energy simulation, HVAC sizing and building operation than previous practice. As a matter of fact, usually simplifications are used (0.5 clo in the summer, 1.0 in the winter). This may lead to systems that are incorrectly sized and/or operated. A model that is able to predict how building occupants change their clothing would greatly improve HVAC system operation.^[2]

As mentioned, clothing adaptation has an important role in achieving thermal comfort and is probably the most effective adjustment that occupants can make to adapt themselves in a thermal environment. Moreover, clothing variability may also depend on factors unrelated to thermal conditions, such as for a dress code or social influences, style preferences that may differ due to gender or work position. According to ASHRAE-55 standard, only if individuals are freely making adjustments in clothing to suit their thermal preferences, it is acceptable to use a single representative average value for everyone.^[1]

Some basic insulation values can be considered as examples of typical conditions^[13]

naked body: 0;
summer clothing: 0.6 clo;
ski outfit: 2 clo;
light polar equipment: 3 clo;
heavy polar equipment: 4 clo;
polar down duvet: 8 clo.

Temperature of thermal equilibrium

The ambient temperature at which someone's body will be at thermal equilibrium depends on the rate of heat generation per unit area P and the thermal insulance of the clothing R. The empirical formula is:^{[ citation needed ]}

T = 31°C − P·R

or, if R is taken to be the number of clos and P the number of watts per square metre,

T = (31 − 0.155·P·R)°C

Temperature of thermal equilibrium

person in summer dress (shorts and bare torso) at rest (P = 60 W/m², R = 0.4 clo): T = +27 °C;
heavy polar equipment, at rest (P = 60 W/m², R = 4 clo): T = −6 °C;
slow walking in light polar equipment (P = 120 W/m², R = 3 clo): T = −25 °C;
sleeping in a polar duvet (P = 48 W/m², R = 8 clo): T = −28 °C;
fast walking in heavy polar equipment (P = 180 W/m², R = 4 clo) : T = −80 °C.

Related Research Articles

<span class="mw-page-title-main">Clothing</span> Objects worn to cover the body

Clothing is any item worn on the body. Typically, clothing is made of fabrics or textiles, but over time it has included garments made from animal skin and other thin sheets of materials and natural products found in the environment, put together. The wearing of clothing is mostly restricted to human beings and is a feature of all human societies. The amount and type of clothing worn depends on gender, body type, social factors, and geographic considerations. Garments cover the body, footwear covers the feet, gloves cover the hands, while hats and headgear cover the head, and underwear covers the private parts.

Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present.

Thermal insulation is the reduction of heat transfer between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials.

In building design, thermal mass is a property of the matter of a building that requires a flow of heat in order for it to change temperature. In scientific writing the term "heat capacity" is preferred. It is sometimes known as the thermal flywheel effect. The thermal mass of heavy structural elements can be designed to work alongside a construction's lighter thermal resistance components to create energy efficient buildings.

The R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat, in the context of construction. R-value is the temperature difference per unit of heat flux needed to sustain one unit of heat flux between the warmer surface and colder surface of a barrier under steady-state conditions. The measure is therefore equally relevant for lowering energy bills for heating in the winter, for cooling in the summer, and for general comfort.

<span class="mw-page-title-main">Extreme cold weather clothing</span> Clothing for arctic or high altitude conditions

Extreme cold weather clothing is clothing for arctic or mountainous areas. Its primary function is to trap air as an insulator to prevent heat loss from the wearer's body. Secondary and necessary is to conduct water vapor away from the body to keep the insulating layers dry. A shell keeps the wind from disturbing the still air in the insulating layers. In warmer conditions, the shell protects from water intrusion.

Superinsulation is an approach to building design, construction, and retrofitting that dramatically reduces heat loss by using much higher insulation levels and airtightness than average. Superinsulation is one of the ancestors of the passive house approach.

Underfloor heating and cooling is a form of central heating and cooling that achieves indoor climate control for thermal comfort using hydronic or electrical heating elements embedded in a floor. Heating is achieved by conduction, radiation and convection. Use of underfloor heating dates back to the Neoglacial and Neolithic periods.

Building insulation is material used in a building to reduce the flow of thermal energy. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation. Often an insulation material will be chosen for its ability to perform several of these functions at once.

<span class="mw-page-title-main">Thermal comfort</span> Satisfaction with the thermal environment

Thermal comfort is the condition of mind that expresses subjective satisfaction with the thermal environment. The human body can be viewed as a heat engine where food is the input energy. The human body will release excess heat into the environment, so the body can continue to operate. The heat transfer is proportional to temperature difference. In cold environments, the body loses more heat to the environment and in hot environments the body does not release enough heat. Both the hot and cold scenarios lead to discomfort. Maintaining this standard of thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC design engineers.

A thermal bridge, also called a cold bridge, heat bridge, or thermal bypass, is an area or component of an object which has higher thermal conductivity than the surrounding materials, creating a path of least resistance for heat transfer. Thermal bridges result in an overall reduction in thermal resistance of the object. The term is frequently discussed in the context of a building's thermal envelope where thermal bridges result in heat transfer into or out of conditioned space.

The tog is a measure of thermal insulance of a unit area, also known as thermal resistance. It is commonly used in the textile industry and often seen quoted on household items such as duvets, sleeping bags and carpet underlay.

PrimaLoft® is a brand of patented synthetic microfiber thermal insulation material that was developed for the United States Army in the 1980s. PrimaLoft is a registered trademark of PrimaLoft, Inc., the brand's parent company.

Dynamic insulation is a form of insulation where cool outside air flowing through the thermal insulation in the envelope of a building will pick up heat from the insulation fibres. Buildings can be designed to exploit this to reduce the transmission heat loss (U-value) and to provide pre-warmed, draft free air to interior spaces. This is known as dynamic insulation since the U-value is no longer constant for a given wall or roof construction but varies with the speed of the air flowing through the insulation. Dynamic insulation is different from breathing walls. The positive aspects of dynamic insulation need to be weighed against the more conventional approach to building design which is to create an airtight envelope and provide appropriate ventilation using either natural ventilation or mechanical ventilation with heat recovery. The air-tight approach to building envelope design, unlike dynamic insulation, results in a building envelope that provides a consistent performance in terms of heat loss and risk of interstitial condensation that is independent of wind speed and direction. Under certain wind conditions a dynamically insulated building can have a higher heat transmission loss than an air-tight building with the same thickness of insulation. Often the air enters at about 15 °C.

Comfort is a sense of physical or psychological ease, often characterised as a lack of hardship. Persons who are lacking in comfort are uncomfortable, or experiencing discomfort. A degree of psychological comfort can be achieved by recreating experiences that are associated with pleasant memories, such as engaging in familiar activities, maintaining the presence of familiar objects, and consumption of comfort foods. Comfort is a particular concern in health care, as providing comfort to the sick and injured is one goal of healthcare, and can facilitate recovery. Persons who are surrounded with things that provide psychological comfort may be described as being "in their comfort zone". Because of the personal nature of positive associations, psychological comfort is highly subjective.

Radiant heating and cooling is a category of HVAC technologies that exchange heat by both convection and radiation with the environments they are designed to heat or cool. There are many subcategories of radiant heating and cooling, including: "radiant ceiling panels", "embedded surface systems", "thermally active building systems", and infrared heaters. According to some definitions, a technology is only included in this category if radiation comprises more than 50% of its heat exchange with the environment; therefore technologies such as radiators and chilled beams are usually not considered radiant heating or cooling. Within this category, it is practical to distinguish between high temperature radiant heating, and radiant heating or cooling with more moderate source temperatures. This article mainly addresses radiant heating and cooling with moderate source temperatures, used to heat or cool indoor environments. Moderate temperature radiant heating and cooling is usually composed of relatively large surfaces that are internally heated or cooled using hydronic or electrical sources. For high temperature indoor or outdoor radiant heating, see: Infrared heater. For snow melt applications see: Snowmelt system.

The thermal manikin is a human model designed for scientific testing of thermal environments without the risk or inaccuracies inherent in human subject testing. Thermal manikins are primarily used in automotive, indoor environment, outdoor environment, military and clothing research. The first thermal manikins in the 1940s were developed by the US Army and consisted of one whole-body sampling zone. Modern-day manikins can have over 30 individually controlled zones. Each zone contains a heating element and temperature sensors within the “skin” of the manikin. This allows the control software to heat the manikin to a normal human body temperature, while logging the amount of power necessary to do so in each zone and the temperature of that zone.

ANSI/ASHRAE Standard 55: Thermal Environmental Conditions for Human Occupancy is an American National Standard published by ASHRAE that establishes the ranges of indoor environmental conditions to achieve acceptable thermal comfort for occupants of buildings. It was first published in 1966, and since 2004 has been updated every three to six years. The most recent version of the standard was published in 2023.

Textile performance, also known as fitness for purpose, is a textile's capacity to withstand various conditions, environments, and hazards, qualifying it for particular uses. The performance of textile products influences their appearance, comfort, durability, and protection. Different textile applications require a different set of performance parameters. As a result, the specifications determine the level of performance of a textile product. Textile testing certifies the product's conformity to buying specification. It describes product manufactured for non-aesthetic purposes, where fitness for purpose is the primary criterion. Engineering of high-performance fabrics presents a unique set of challenges.

Clothing physiology is a branch of science that studies the interaction between clothing and the human body, with a particular focus on how clothing affects the physiological and psychological responses of individuals to different environmental conditions. The goal of clothing physiology research is to develop a better understanding of how clothing can be designed to optimize comfort, performance, and protection for individuals in various settings, including outdoor recreation, occupational environments, and medical contexts.

References

1 2 3 4 5 ANSI/ASHRAE Standard 55-2010, Thermal Environmental Conditions for Human Occupancy
1 2 Schiavon, S.; Lee, K. "H. (2012), Dynamic predictive clothing insulation models based on outdoor air and indoor operative temperatures" (PDF). Building and Environment. 59: 250–260. doi:10.1016/j.buildenv.2012.08.024.
↑ Cubrić, Ivana Salopek; Skenderi, Zenun (March 2013). "Evaluating thermophysiological comfort using the principles of sensory analysis". Collegium Antropologicum. 37 (1): 57–64. ISSN 0350-6134. PMID 23697251.
↑ Song, Guowen (2011-01-20). Improving Comfort in Clothing. Elsevier. p. 114. ISBN 978-0-85709-064-5.
↑ Stevens, Katy (2008). Thermophysiological comfort and water resistant protection in soft shell protective garments. University of Leeds (School of Design).
↑ Textile Trends. Eastland Publications. 2001. p. 16.
↑ Conference, Textile Institute (Manchester, England) (1988). Pre-print of Conference Proceedings: Textile Institute 1988 Annual World Conference, Sydney, Australia, 10-13 July. Textile Institute. p. 9. ISBN 978-1-870812-08-5.{{cite book}}: CS1 maint: multiple names: authors list (link)
↑ Ruckman, J.E.; Murray, R.; Choi, H.S. (1999-01-01). "Engineering of clothing systems for improved thermophysiological comfort: The effect of openings". International Journal of Clothing Science and Technology. 11 (1): 37–52. doi:10.1108/09556229910258098. ISSN 0955-6222.
↑ Varshney, R. K.; Kothari, V. K.; Dhamija, S. (2010-05-17). "A study on thermophysiological comfort properties of fabrics in relation to constituent fibre fineness and cross-sectional shapes". The Journal of the Textile Institute. 101 (6): 495–505. doi:10.1080/00405000802542184. ISSN 0040-5000. S2CID 135786524.
↑ Collier, Billie J. (2000). Understanding textiles. Internet Archive. Upper Saddle River, NJ : Prentice Hall. p. 539. ISBN 978-0-13-021951-0.
1 2 3 4 Thermal Comfort chapter, Fundamentals volume of the ASHRAE Handbook , ASHRAE, Inc., Atlanta, GA, 2005.
↑ ""U.S. Soldiers in Alaska Get Super-Warm Togs". The Science News-Letter. Vol. 39, No. 8 (Feb. 22, 1941), pp. 124-125. Published by: Society for Science & the Public". JSTOR 3917809.{{cite journal}}: Cite journal requires |journal= (help)
↑ Notes for course "Human Factors: Ambient Environment" by Prof. Alan Hedge, Cornell University

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[Ashrae_55_Standard-1] 1 2 3 4 5 ANSI/ASHRAE Standard 55-2010, Thermal Environmental Conditions for Human Occupancy

[Schiavon_&_Lee,_2012-2] 1 2 Schiavon, S.; Lee, K. "H. (2012), Dynamic predictive clothing insulation models based on outdoor air and indoor operative temperatures" (PDF). Building and Environment. 59: 250–260. doi:10.1016/j.buildenv.2012.08.024.

[3] Cubrić, Ivana Salopek; Skenderi, Zenun (March 2013). "Evaluating thermophysiological comfort using the principles of sensory analysis". Collegium Antropologicum. 37 (1): 57–64. ISSN 0350-6134. PMID 23697251.

[4] Song, Guowen (2011-01-20). Improving Comfort in Clothing. Elsevier. p. 114. ISBN 978-0-85709-064-5.

[5] Stevens, Katy (2008). Thermophysiological comfort and water resistant protection in soft shell protective garments. University of Leeds (School of Design).

[6] Textile Trends. Eastland Publications. 2001. p. 16.

[7] Conference, Textile Institute (Manchester, England) (1988). Pre-print of Conference Proceedings: Textile Institute 1988 Annual World Conference, Sydney, Australia, 10-13 July. Textile Institute. p. 9. ISBN 978-1-870812-08-5.{{cite book}}: CS1 maint: multiple names: authors list (link)

[8] Ruckman, J.E.; Murray, R.; Choi, H.S. (1999-01-01). "Engineering of clothing systems for improved thermophysiological comfort: The effect of openings". International Journal of Clothing Science and Technology. 11 (1): 37–52. doi:10.1108/09556229910258098. ISSN 0955-6222.

[9] Varshney, R. K.; Kothari, V. K.; Dhamija, S. (2010-05-17). "A study on thermophysiological comfort properties of fabrics in relation to constituent fibre fineness and cross-sectional shapes". The Journal of the Textile Institute. 101 (6): 495–505. doi:10.1080/00405000802542184. ISSN 0040-5000. S2CID 135786524.

[10] Collier, Billie J. (2000). Understanding textiles. Internet Archive. Upper Saddle River, NJ : Prentice Hall. p. 539. ISBN 978-0-13-021951-0.

[ASHRAE_Fundamentals-11] 1 2 3 4 Thermal Comfort chapter, Fundamentals volume of the ASHRAE Handbook , ASHRAE, Inc., Atlanta, GA, 2005.

[tog-12] ""U.S. Soldiers in Alaska Get Super-Warm Togs". The Science News-Letter. Vol. 39, No. 8 (Feb. 22, 1941), pp. 124-125. Published by: Society for Science & the Public". JSTOR 3917809.{{cite journal}}: Cite journal requires |journal= (help)

[13] Notes for course "Human Factors: Ambient Environment" by Prof. Alan Hedge, Cornell University

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