[esp-r] Re: Types of glass

[Jon Hand (clcv10)]

A recent question about optical properties (outside and inside panes)

> The absorptions at the external and internal clear float glass  
> layers are taken from DCF7671_06nb, which appear to be:
> 0.157 0.172 0.185 0.201 0.202
> 0.117 0.124 0.127 0.112 0.077

The treatment of optical properties, as calculated by tools such as  
WIS and
Window 5.2 and used by simulation tools such as ESP-r are based on
absorption being calculated from the outside to the inside.

The absorption of an inner layer, is, by tradition, calculated  
"relative" to that of
an outer layers.  Another way of saying this is if 100 units reach  
the outer glass
and it absorbs 40 units any inside layers of glass can only know  
about the
remaining 60 units rather than the initial 100 units.  The values  
seen in the
optical database take this into account.

In ESP-r the thermophysical properties of glass are held separately from
the optial properties of the glass.  A thermophysical material  
labeled as
clear float might have a range of possible optical properties.  It is  
up to
authors that define databases and the links between databases to ensure
that the names of the entities are clear and the correct associations
are defined.  It is certainly the case that some of the names that have
been given to database entities are a bit opaque.  We are working  
towards
allowing longer (and hopefully more expressive names).

-ESRU
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