Two diverse environmental requirements have stimulated the production and use of various forms of double and triple glazing: a desire for improved heat insulation and the need for protection against external noise. The essential difference between double glazing designs to meet these two needs lies in the width of the air space. For heat insulation, air-space widths as small as 6 mm are of some value; for sound insulation, air-space widths of not less than 100 mm, and preferably more, are essential but there are other factors which are also discussed in this Digest
