Difference between revisions of "Tog (unit)"

Latest revision as of 09:16, 20 September 2010

The tog is a measure of thermal resistance, commonly used in the textile industry, and often seen quoted on, for example, duvets and carpet underlay. The word may come from toga, a Roman garment from which the English slang togs (meaning clothes) is probably derived.

The basic unit of insulation coefficient is the R_SI, (1 m² K / watt). 1 tog = 0.1 R_SI. There is also a clo clothing unit equivalent to 0.155 R_SI or 1.55 tog ^[1] 1 tog is roughly equivalent to the insulation provided by one broad sheet newspaper in dry conditions.

The Shirley Institute in Britain developed the tog as an easy-to-follow alternative to the SI unit of m²K/W. Launched in the 1960s, the Shirley Togmeter is the standard apparatus for rating thermal resistance of textiles, commonly known as the Tog Test.

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.

According to British retailer John Lewis, tog guidelines for duvets are as follows:^[2]

A few enterprising manufacturers have marketed combined duvet sets consisting of two duvets; one of approximately 4.5 tog and one of approximately 9.5 tog. These can be used individually as summer (4.5 tog) and spring/autumn (9.5 tog). When joined together using press studs around the edges, or Velcro strips across each of the corners, they become a 14 tog winter duvet and as such can be made to suit all seasons.

Notes

1. ↑ Cornell University Ergonomics Web
2. ↑ John Lewis Partnership website