This Standard specifies the assumptions to be used in calculating the system R-values and total R-values of building constructions, which include IR reflective or IR non-reflective airspaces, for the purposes of designing building components to be used in thermal insulation systems.   NZS 4859.2:2018 D N Z N C , , A N t 0 N N O J Australian/New Zealand Standard" Thermal insulation materials for buildings Part 2: Design /1-. i STANDARDS？, . JAML au/ NEW ZEALAND AS/NZS 4859.2:2018 This Joint Australian/New Zealand Standard was prepared by Joint Technical Committee BD-058, Thermal Insulation. It was approved on behalf of the Council of Standards Australia on 8 October 2018 and by the New Zeala