The development
of hard low emissivity coatings widens the possibility
of including coated monolithic glazing in secondary
frames applied to existing windows; the earlier,
softer low emissivity coatings were restricted
to protected use in sealed glazed units only.
Metallic surfaces, including some metallic oxides,
provide low emissivity.
Water on the
coated surface of the glass, perhaps as a result
of condensation, will cancel out the effect of
the Low E coating because of the high emissivity
of water.
The present
technology of on-line, hard Low E coatings can
provide slightly higher solar heat transmission
than that exhibited by soft coatings, giving improvements
to passive solar gain applications. In cold climates
the higher temperature of the inner glass surface
of double glazed units using Low E coatings diminishes
the effect of colder long wave radiation causing
discomfort near the window.
