The single glazing that was standard up until the mid 1970s was characterised by high heat loss (Ug = 5.0 W/m2K). Increased use of double glazing brought improved Ug values of an average of 3.0 W/m2K. Further reductions in heat loss followed with the application of modern thin-film coatings. Today double glazing with a Ug value of 1.1 W/m2K with...