Fill power refers to the capacity of a down product to trap air and hold it. The rule of thumb is the higher the fill power the better the product will trap air and insulate. In the case of a duvet, your body heat doesn’t escape from beneath the duvet and keeps you warm.
The numerous codes and testing methods applied by the different world players makes it difficult to compare products, for example in the United States a sample of 28.4 grams is tested while industry players in Europe continue to debate whether 30 or 20 grams should be used.
In the early years, the fill capacity was indicated by the breakdown of the fill material in percentage, for example in 1975, Piumini Danesi® pooq dene® duvets were labelled 98% goose down and 2% semiplumes. Due to the discovery of faudulent labelling practices, the Swedish standard SIS 705015 (weight/volume test) was adopted and mainly used in Northern Europe. The test used a 20 gram sampling of down and measured its fill power on a scale from 1 to 12. Piumini Danesi pooq dene ensured their fill always registered a value between 10,5 and 11.
With the liberalisation of the European market, the European Union member states in the late 90s set out to establish a single index for Europe. SIS 705015 was replaced by the following EU standards on feather and down which remain in force:
EN 12130 (1998) Test methods. Determination of the filling power (massic volume)
EN 12934 (1999) Composition labelling of processed feathers and down for use as sole filling material
EN 13186 (2004) Specification for feather and down filled bedding articles.
While the test remains the same, 20 grams of down tested under pressure, the unit of measurement has changed, the fill power values range from 3 to 13 cm. The obtained value is then transformed into g/cm³ to determine the volumetric meausere which ranges from 199 to 400+ g/cm³. Piumini Danesi pooq dene registers maximum values of 13 cm and 440 g/cm³.
In the United States, the fill power standard of measurement is calculated in ounces/inch³ (oz/in³) based on a scale that ranges from 200 to 800+ oz/in³. In England, the TOG rating is used, which measures the thermal resistance or warmth of a product at a given time, not taking into account the quality of the fill, Another unit of measurement used in Anglo-Saxon countries is the CU IN (cubic inch) which simply indicates the amount of filling expressed in volume.