A	auxiliary parameter [m3]
a	width (of glass pane) [m]
B	auxiliary parameter [m5/kN]
b	length (of glass pane) [m]
c	auxiliary parameter [kPa]
D	flexural rigidity (of glass pane) [kNm]
d	thickness (of glass pane) [m] or [mm]
E	Young’s modulus [kPa] or [GPa]
h	thermal conductance [W/(m2·K)]
i	consecutive natural number
Nu	Nusselt number
p	pressure [kPa]
q	load per area, [kN/m2]
R	thermal resistance [(m2·K)/W]
s	thickness (of gas gap) [mm]
T	temperature (of gas in the gap) [K]
t	temperature (of air) [K] or [°C]
U	thermal transmittance [W/(m2·K)]
V	wind velocity [km/h]
v	volume (of the gap) [m3]
w	deflection [mm]
w(x,y)	function of deflection, [m]
x-y	coordinate system
Greek letters
α	proportionality factor, [m5/kN]
α’	dimensionless coefficient [-]
βi	auxiliary parameter [-]
∆p	pressure change [kPa]
∆T	temperature difference [K]
∆v	volume change [m3]
∆Φ	percentage increase in density of heat-flow rate [%]
ε	surface emissivity [-]
λ	thermal conductivity [W/(m·K)]
μ	Poisson’s ratio [-]
π	number “pi”
σ	Boltzmann constant [W/(m2·K4)]
Φ	density of heat-flow rate [W/m2]
Subscripts and markings
0	initial gas parameters
1, 2	specific gas-filled gap
1-2	glass pane (between gaps)
c	center (of glass pane)
a	atmospheric
e	external
ex	exterior glass pane
g	regarding gas or regarding IGU (at Ug, Φg and ∆Φg)
i	internal
in	interior glass pane
m	mean, average
op	operating gas parameters
r	radiative
s	regarding gas gap
sur1, sur2	regarding surfaces
v	regarding volume
w	regarding deflection
z	outside