Fiber Glass

There are no industry or government standards that address settlement of fiber glass insulation, in spite of the fact that several studies indicate blown fiber glass settles. The FTC R-Value Rule acknowledges that fiber glass settles, but contains no provisions requiring manufacturers to account for loss of thickness after installation. Settlement will be greatest (and the R-value less) if the material is deliberately fluffed during installation, an all too common occurrence. ASTM has adopted a test method that can accurately determine the installed thickness of any loose-fill insulation. If manufacturers use this test accurate coverage charts can be developed.