Tog (unit)
Encyclopedia
The tog is a measure of thermal resistance of a unit area, also known as thermal insulance, commonly used in the textile industry
, and often seen quoted on, for example, duvet
s and carpet underlay
.
The Shirley Institute
in Manchester, England developed the tog as an easy-to-follow alternative to the SI
unit of m2K/W. The name comes from the informal word "togs" for clothing which itself was probably derived from the word toga
, a Roman garment.
The basic unit of insulation coefficient is the RSI
, (1 m² K / Watt). 1 tog = 0.1 RSI. There is also a clo
clothing unit equivalent to 0.155 RSI or 1.55 tog.
A tog is 0.1 m2K/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
per square metre.
British duvets are sold in steps of 1.5 tog from 4.5 tog (summer) to 15 tog (extra-warm). The stated values are minima, actual values may be up to 3 tog higher.
According to British retailer John Lewis
, tog guidelines for duvets are as follows:
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
strips across each of the corners, they become a 13.5 tog winter duvet and as such can be made to suit all seasons.
Each industry has its own specifications and methods for measuring thermal properties. The Shirley Togmeter is unsuitable for duvets because the large scale of their quilted construction makes it impractical to obtain a representative sample of suitable size. BS5335 describes apparatus for duvet tog testing. This consists of a metal plate at least 1000mm x 600mm at skin temperature (33°C) arranged to support the whole duvet, and a mechanism for measuring the air temperature above the quilt. This requires very precise control of the laboratory environment in order to get reliable results.
BS8510 describes tog testing for baby products, the concern here being to ensure that babies do not overheat.
Measurement of the clo, a similar measure used in the USA, is described in ASTM D-1518.
Textile industry
The textile industry is primarily concerned with the production of yarn, and cloth and the subsequent design or manufacture of clothing and their distribution. The raw material may be natural, or synthetic using products of the chemical industry....
, and often seen quoted on, for example, duvet
Duvet
A duvet from the French duvet "down"), is a type of bedding — a soft flat bag filled with down, feathers, or a synthetic alternative, and protected with a removable cover, analogous to a pillow and pillow case...
s and carpet underlay
Underlay
Underlay or underlayment generally refers to a thin layer of cushioning made of materials such as sponge rubber, foam, felt, or crumb rubber; this material is laid beneath carpeting to provide comfort underfoot, to reduce wear on the carpet, and to provide insulation against sound, moisture, and...
.
The Shirley Institute
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...
in Manchester, England developed the tog as an easy-to-follow alternative to the SI
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...
unit of m2K/W. The name comes from the informal word "togs" for clothing which itself was probably derived from the word toga
Toga
The toga, a distinctive garment of Ancient Rome, was a cloth of perhaps 20 ft in length which was wrapped around the body and was generally worn over a tunic. The toga was made of wool, and the tunic under it often was made of linen. After the 2nd century BC, the toga was a garment worn...
, a Roman garment.
The basic unit of insulation coefficient is the RSI
R-value (insulation)
The R-value is a measure of thermal resistance used in the building and construction industry. Under uniform conditions it is the ratio of the temperature difference across an insulator and the heat flux through it or R = \Delta T/\dot Q_A.The R-value being discussed is the unit thermal resistance...
, (1 m² K / Watt). 1 tog = 0.1 RSI. There is also a clo
Thermal comfort
Thermal comfort is a term used by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, an international body. It is defined as the state of mind in humans that expresses satisfaction with the surrounding environment...
clothing unit equivalent to 0.155 RSI or 1.55 tog.
A tog is 0.1 m2K/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
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
per square metre.
British duvets are sold in steps of 1.5 tog from 4.5 tog (summer) to 15 tog (extra-warm). The stated values are minima, actual values may be up to 3 tog higher.
According to British retailer John Lewis
John Lewis Partnership
The John Lewis Partnership is an employee-owned UK partnership which operates John Lewis department stores, Waitrose supermarkets and a number of other services...
, tog guidelines for duvets are as follows:
| Lightweight summer duvet: | 4.5 tog |
| Spring/Autumn weight duvet: | 9.0 - 10.5 tog |
| Winter weight duvet: | 12.0 - 13.5 tog |
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
Velcro is the brand name of the first commercially marketed fabric hook-and-loop fastener, invented in 1948 by the Swiss electrical engineer George de Mestral...
strips across each of the corners, they become a 13.5 tog winter duvet and as such can be made to suit all seasons.
Tog Testing
Launched in the 1940s, the Shirley Togmeter is the standard apparatus for rating thermal resistance of textiles, commonly known as the Tog Test. This apparatus, described in BS4745 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. The Shirley Togmeter is unsuitable for duvets because the large scale of their quilted construction makes it impractical to obtain a representative sample of suitable size. BS5335 describes apparatus for duvet tog testing. This consists of a metal plate at least 1000mm x 600mm at skin temperature (33°C) arranged to support the whole duvet, and a mechanism for measuring the air temperature above the quilt. This requires very precise control of the laboratory environment in order to get reliable results.
BS8510 describes tog testing for baby products, the concern here being to ensure that babies do not overheat.
Measurement of the clo, a similar measure used in the USA, is described in ASTM D-1518.