Meet the duvets

Tog

Tog is a measure of warmth (not comfort) of an item of bedding

Tog is a measure of warmth (not comfort) of an item of bedding, especially duvets. It is a quintessential English standard of measure not found in other parts of the world.

Wikipedia has the following to say about it:

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 RSI, (1 m² K / watt). 1 tog = 0.1 RSI.

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 Togmetre 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:

The tog rating of an item is therefore affected by a number of factors, not least the type of fibre under consideration. Some manufacturers of wool duvets maintain that tog ratings should only be applied to synthetic fibre and not natural fibres like wool. Our Southdown duvets contain 350gr of pure wool per square metre of duvet.

This equates to a 7.4 tog which presents an all-weather, all-year duvet most commonly sold, for example, in Germany.

Our reasoning behind an all-purpose duvet is simple - we don’t expect our customers to have buy two duvets of differing weights to get a decent night’s sleep all year round or to have to buy two light weight duvets and then have to Velcro them together in winter.

The other important factor is that tog measures thermal resistance and not levels of comfort which, with duvets, are two totally different things. A very warm duvet with a 13.5 tog might appear to be ideal but can turn out to be very heavy if its alpaca, for example, or it might result in disturbing night sweats if it’s synthetic.

A feather/down duvet with a medium tog might offer the right warmth but the fill might clump,and cause hot and cold spots in the duvet or aggravate asthma or allergies.

Compare

	Wool	Synthetic	Feather/Down	Pure Down
Wicking absorbs moisture
Breathable
Sustainable
Cruelty Free		N/A
Chemical Free
Flame Retardant
Dust mite free
Hypoallergenic
Level Of Comfort	HIGH	LOW	MEDIUM	HIGH