The term used when referring to the denseness of a quilt set is Thermal Overall Grade and is the measure of thermal resistance/insulation per unit area. It was developed by an Institute in Manchester as a simple alternative to the SI unit of m2K/W, and is used mainly by the textile industry. It is a representative of how warm a duvet is, not how heavy or thick. It is also based on how well the duvet can trap warm air, thus providing more insulation. Natural filled duvets have a higher rating than synthetic filled ones. The seasonal tog guidelines set by all well known retailers are between 4.5 and 13.5 the lowest being the spring months and the highest being the winter months.
Some manufacturers have developed a pair of these products which can be combined together using press studs or Velcro. This enables you to put them together should one or the other not be warm enough. These Manufacturers also provide duvets that have two halves with two different tog ratings, this is for those people who share a duvet but may have an alternative resistance to the cold.
King Bedspread Set
Natural filling can consist of feathers or down from geese and ducks, and are great at trapping air which is considered to be an effective form of insulation. Goose feathers are lighter than duck feathers; however, they still provide the same amount of warmth. They have long life spans, a top quality one will last you approximately thirty years. However, they need to be professionally washed and dried or their life span and insulation ability will diminish.
Synthetic filling is good, however, if you have allergies especially asthma the duvets need to be washed frequently at home. Some synthetic duvets can be washed at 60oC, this is the temperature required to get rid of dust mites. They don't provide as much insulation or last as long as natural fillings, but they can be light and can last up to ten years if they're good quality.
Because children only need small quilt sets which trap more air and provide more insulation than adult duvets, they should only have a tog rating of 4.5-9.0; unless their room is especially cold. Duvets and pillows are not recommended for those under twelve months, and health professionals suggest a room temperature of about 18oC. This is important as newborn babies cannot regulate their own body temperature properly, and overheating in babies is a common cause of cot death.