desired; this data can  then    Multi-band   Solar   Optical
be  saved  as  a new glazing    Properties:
type and assigned a  library
number.  The default however         The    second    option
is to  use the properties as    available at this point, the
they  appear  on  the screen    F4 option, allows  the  user
and to use the enter key  to    to override the default cal-
go  on  to  the next glazing    culated one band  values  of
layer.   This   process   is    the   glazing  system  solar
repeated for as many glazing    transmittance and individual
layers as  were  defined  on    layer   solar   absorptances
the first screen.  Note that    (Figure 5).   The  procedure
the glazing material  thick-    used   to   calculate  these
ness is now a required input    values is  based  on  a  one
since the  glazing  material    (total solar) band approach.
resistances  are used in the    In cases where two  or  more
calculation procedure.          spectrally selective (within
                                the solar spectrum)  glazing
Frame and Edge Effects:         products are used, such as a
                                double  glazed  system  with
     Once  all  layers  have    green tinted glass and glaz-
been   defined,  two  window    ing with a low-e coating,  a
system  options  are  avail-    multi-band  model  should be
able.  F3, the first option,    used.  We are in the process
allows the user to choose  a    of  revising SPECTRUM 1.1 to
frame   option  (Figure  4).    be  able  to  generate  this
This screen can  be  ignored    data.
if   the  user  only  wishes
center-of-glass     results.    Gaps and Gas Fills:
WINDOW  3.0  will  calculate
center of glass U-values, IG         After  the  above   two
U-values  which  include  an    options  (  F3 and F4 ) have
edge effect, and  window  U-    been used or  skipped  over,
values   which  include  the    the   gap   width/gas   type
frame effect.   At  present,    screen will  appear  (Figure
we  are  using  edge  effect    6).   For each gap, the user
data  submitted  to   ASHRAE    must define a gap thickness,
TC4.5   (Fenestration)   for    and choose a gas or gas mix-
glazing systems  with  metal    ture.  Choosing a  gas  mix-
spacers  and  the  frame  U-    ture will prompt the user to
value  data  shown  on   the    specify the appropriate per-
frame  screen.   This  is an    centages   of   the   gasses
extension of  the  data  and    chosen.  Data for  gas  mix-
methodology reported in [2].    tures  is  based  on regres-
We hope to  include  similar    sions to  gas  mixture  data
data for alternative spacers    calculated analytically [3].
(i.e.   butyl,   fiberglass,    Gas type 16 allows the  user
glassedge).   Note  that the    to temporarily enter the gas
edge area is defined as  the    library in order to define a
perimeter    glazing    area    new  gas  and enter its pro-
within 2.5" of the IG unit's    perties or to see  the  pro-
sight line and that the pro-    perties   of   the  existing
jected frame width is 1.5".     gasses (Figure 7).   If  one
                                of  gas  types 5-8 (gas mix-
