Low-E Glazing: Should External Emissivity Be <0.9?

Looking at the parameters of the default setting for external glazing [e.g. low-e double glazing (6mm+6mm) (2002 regs) in Apache Constructions Database], as this is a 'low e' glazing unit, should the emissivity of the external surface of the glazing unit be less than 0.9? Something in the order of 0.3 or even 0.16 for Pilkington Energy advantage 'low e'?

The special coatings for almost all 'low-e' glazing systems face into the cavity, so do not affect the emissivities on their outer surfaces. These have a value appropriate for glass, i.e. about 0.9. The low-e coatings are taken into account via an increase in the cavity resistance.

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