The tog is a measure of

thermal insulance In the context of construction, 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. R-value is the temperature difference per ...

of a unit area, also known as

thermal resistance Thermal resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow. Thermal resistance is the reciprocal of thermal conductance. * (Absolute) thermal resistance ''R'' in kelvi ...

. It is commonly used in the

textile industry The textile industry is primarily concerned with the design, production and distribution of yarn, cloth and clothing. The raw material may be natural, or synthetic using products of the chemical industry. Industry process Cotton manufactu ...

and often seen quoted on, for example,

duvet A duvet (, ; ), usually called a comforter or (''down-filled'') quilt in US English, and a doona in Australian English, is a type of bedding consisting of a soft flat bag filled with either down, feathers, wool, cotton, silk, or a synthetic ...

s and carpet

underlay Underlay may refer to flooring or roofing materials, bed padding, or a musical notation. Flooring Underlay or underlayment"Underlayment." ''The Oxford English Dictionary''. 2nd ed. 1989. generally refers to a thin layer of cushioning made of mate ...

. The

Shirley Institute The Shirley Institute was established in 1920 as the British Cotton Industry Research Association at The Towers in Didsbury, Manchester, as a research centre dedicated to cotton production technologies. It was funded by the Cotton Board throug ...

in Manchester, England developed the tog as an easy-to-follow alternative to the SI unit of m²⋅K/W. The name comes from the informal word ''togs'' for 'clothing', which itself was probably derived from the word ''

toga The toga (, ), a distinctive garment of ancient Rome, was a roughly semicircular cloth, between in length, draped over the shoulders and around the body. It was usually woven from white wool, and was worn over a tunic. In Roman historical tr ...

'', a Roman garment. The

backronym A backronym is an acronym formed from an already existing word by expanding its letters into the words of a phrase. Backronyms may be invented with either serious or humorous intent, or they may be a type of false etymology or folk etymology. The ...

''thermal overall grade'' is also attested. The basic unit of insulation coefficient is the ''R''_SI, (1 m²⋅K/W). 1 tog = 0.1 ''R''_SI. There is also a US clothing unit, the clo, equivalent to 0.155 ''R''_SI or 1.55 tog, described in ASTM D-1518. A tog is 0.1 m²⋅K/W. In other words, the thermal resistance in togs is equal to ten times the temperature difference (in °C) between the two surfaces of a material, when the flow of heat is equal to one

watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Watt ...

per square metre. British duvets are sold in steps of 1.5 tog from 3.0 tog (summer) to 16.5 tog (extra-warm). The stated values are a minimum; actual values may be up to 3 tog higher. Also, these values assume there is no added duvet cover that can trap air. A few manufacturers have marketed combined duvet sets consisting of two duvets; one of approximately 4.5 tog and one of approximately 9.0 tog. These can be used individually as summer (4.5 tog) and spring/autumn (9.0 tog). When joined together using press studs around the edges, or

Velcro Velcro, officially known as Velcro IP Holdings LLC and trading as Velcro Companies, is a British privately held company, founded by Swiss electrical engineer George de Mestral in the 1950s. It is the original manufacturer of hook-and-loop fasten ...

strips across each of the corners, they become a 13.5 tog winter duvet and as such can be made to suit all seasons.

Testing

Launched in the 1940s by the

, the Shirley Togmeter is the standard apparatus for rating thermal resistance of textiles, commonly known as the Tog Test. This apparatus, described in BS 4745:2005, measures a sample of textile, either between two metal plates (for underclothing) or between a metal plate and free air (for outer layers). Each industry has its own specifications and methods for measuring thermal properties.

References

{{DEFAULTSORT:Tog (Unit) Thermodynamics Textiles Units of measurement

Testing

See also

References