US-European R Value Convertion Tables
A source of ingoing confusion is the difference between R values in the US and "SI" R values in Europe (and here in New Zealand).
As an example; an R 4.0 fiberglass Pink Batt in New Zealand would be labeled "R-23" in the USA. This is important to keep in mind when reading about insulation online.
Convert US R-values to European metric R values
Convert European metric R values to US R-values
To convert IP R-values to metric R-values, multiply by 0.1761. Source: http://en.wikibooks.org/wiki/Straw_Bale_Construction/Characteristics/Insulation
Also: http://www.allwallsystem.com/design/RValueTable.html (US R values)