Compressible insulation element with reduced friction

A method of installing an insulation product comprising a compressible insulation element between a pair of beams or rafters, comprising the steps of:

• providing a compressible mineral fiber insulation element having a first major surface opposed to a second major surface, and having side surfaces connecting the first and second major surfaces and defining a thickness of the insulation element, said thickness being at least 10 cm, said insulation element having a first facing which is attached to at least a part of said first major surface and which is provided with at least one extension flange having an outer end and where said outer end is not directly secured to said insulation element and where an outer surface of said extension flange has a coefficient of friction in relation to a wood surface which is smaller than a coefficient of friction of a side surface of the mineral fiber insulation in relation to the same wood surface, a second facing on said second major surface of said insulation element which is provided with flanges extending beyond said second major surface, wherein neither said first facing or said second facing is directly attached to a major part of each of the side surfaces of the insulation element and said extension flange and said flanges of said second facing are not directly joined;
• covering at least a part of at least one side surface with said extension flange with said outer end thereof being on said at least one side surface;
• and
• introducing the insulation element in between a pair of beams or rafters with said first major surface with the first facing attached thereto entering first.