BS 6993-1:1989

Foreword
Committees responsible
Method
1 Scope
2 Definitions
3 Symbols
4 Basic equations
5 Basic material properties
6 Exterior and interior heat transfer coefficients
7 Standardized values
8 Accuracy
Appendices
A Emissivity
B Gas properties
C Heat transfer coefficients
D Examples of U-value calculation for standardized
   values
Tables
1 Values of constant C and exponent n
2 Effective emissivity and inter-surface emittance for
   one surface glass, one coated low-emissivity surface
3 Effective emissivity and inter-surface emittance for
   two similarly coated low-emissivity surfaces
4 Hemispherical emissivity, epsilon h
5 Gas properties at 283 K mean
6 Exterior heat transfer coefficients
7 Interior heat transfer coefficients
Figure
1 Variation of U-value with normal emissivity of air
   and argon filled glazing units of 6 mm glass

Method for calculating the U-value in the central area of single, double and multiple glazing with uncoated or two coated low-emissivity surfaces bounding the spaces.