Page 37 - Between light and shade
P. 37

Light, transparency and reflection

   This initial double glazing comprises two
panes of 3-mm-thick float glass set 0.3 mm
apart, between which there is a vacuum. Small
stainless steel cylindrical columns with a diame-
ter of 0.5 mm, positioned every 20 mm in both
directions, prevent the panes being drawn toge-
ther by the vacuum. Traditional double glazing
edge dividers, generally made from synthetic
sealant and a rigid profile (aluminium, steel, etc.)
forming a 20 − 25 mm opaque black edge, reduce
the glazing’s energy performances the smaller
the latter is (what is commonly known as the
edge effect). Moreover, it is not recyclable 21. In
this case it is replaced by a ceramic sinter, which
is less than 6 mm wide, reducing the edge effect
to the bare minimum.

   By stretching the argument, the system has
a number of virtues. In the currently anticipa-
ted versions, its level of thermal insulation is
far superior to what can be achieved with the
best energy performance triple glazing known
to date. The new vacuum glazing produced in
Europe should therefore have a heat transfer
coefficient of U=0.3 W/m2 °K 22, in both a vertical

21	 While the terms “circular economy” and “cradle to cradle” are
     on everyone’s lips, no-one is concerned about the “mountains”
     of aluminium slats, sealants and fragments of glass that are
     piling up in the waste tips of our ports.
22	  The heat transmission coefficient U (in W/m² °K) of 6 mm

     single glazing is 5.7; that of basic double glazing varies between
     2.7 and 3.3; that of the best current insulating glass is 1.0 to 1.2

     37
   32   33   34   35   36   37   38   39   40   41   42