Photo Source: Summerhill Photo Source: Roxul (Rockwool)

Photo Source: Summerhill Photo Source: Summerhill

Installing batts in an empty wall cavity :

Glass fibre batts need to be installed into the cavities created by the framing. All walls that separate the heated area from unheated areas require insulation. Most interior walls do not.

All cavities that require insulation must be filled so that the insulation is flush with the framing members. If the insulation extends out beyond the framing members, it will get compressed and the R-value of that cavity will be reduced. If the cavity is not filled completely with insulation, there will be an air space that creates a convection current to start, which will increase the rate of heat transfer in that cavity.