INNERS

Tog is a measure of thermal resistance – in simple terms, it indicates how warm a duvet will keep you. Developed by the Shirley Institute in the UK, tog was introduced in the 1960s as an easy-to-understand alternative to the scientific SI unit (m?K/W).

Using the Shirley Togmeter – the industry-standard testing apparatus – textiles are measured for their ability to retain heat. The higher the tog rating, the warmer the product.

One tog is equal to 0.1 m?K/W, meaning the thermal resistance in togs is ten times the temperature difference (in ?C) between the two surfaces of a material when heat flow equals one watt per square metre.

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