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<DIV dir=ltr align=left><SPAN class=355085316-22092008><FONT face=Arial
size=2>Table C3.5 from ASHRAE 90.1, 2004 gives baseline Visible Light
Transmission factors which are multiplied by the Solar Heat Gain
Coefficient to determine VLT for the base case when using the envelope trade-off
option for compliance. </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=355085316-22092008><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=355085316-22092008><FONT face=Arial
size=2>Mike</FONT></SPAN></DIV><!-- Converted from text/rtf format -->
<P><B><FONT face=Verdana color=#d47500>__________________________</FONT></B>
</P>
<P><B><FONT face=Verdana>Michael Rosenberg</FONT></B> <BR><FONT face=Verdana
size=2>Senior Commercial Buildings Energy Analyst</FONT> <BR><FONT face=Verdana
size=2>ENERGY & ENVIRONMENT DIRECTORATE </FONT></P>
<P><FONT face=Verdana size=2>Pacific Northwest National Laboratory
</FONT><BR><FONT face=Verdana size=2>2032 Todd Street </FONT><BR><FONT
face=Verdana size=2>Eugene, OR 97405 </FONT><BR><FONT face=Verdana size=2>(541)
844-1960 </FONT><BR><FONT face=Verdana size=2>michael.rosenberg@pnl.gov
</FONT><BR><FONT face=Verdana color=#d47500 size=2>www.pnl.gov</FONT> </P>
<DIV> </DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> bldg-sim-bounces@lists.onebuilding.org
[mailto:bldg-sim-bounces@lists.onebuilding.org] <B>On Behalf Of </B>karen
mozes<BR><B>Sent:</B> Monday, September 22, 2008 9:47 AM<BR><B>To:</B> Josh
Greenfield<BR><B>Cc:</B> equest-users@lists.onebuilding.org;
bldg-sim@lists.onebuilding.org<BR><B>Subject:</B> Re: [Bldg-sim] Glass
center-of-glass to assembly U-Value?<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=ltr>
<DIV>Hi,</DIV>
<DIV>Chapter 31 (Fenestration) of Ashrae handbook fundamentals has average
overall U-values for different frame types (weighted average for a frane of 2.5"
I believe, which also includes the glassedge effect). Accurate U-values need to
be calculated using NFRC standards, using approved software (in the US this is
LBNL Windows and Therm). </DIV>
<DIV> </DIV>
<DIV>I am not aware of a visible light transmittance requirement, but the lower
the transmittance, the less daylighting benefits you will get, as you know, so
there are no energy benefits for having a low Vt. Glass manufacturers work
hard to keep light transmittances high and SHGC low.</DIV>
<DIV> </DIV>
<DIV>Hope this helps</DIV>
<DIV>Kind regards,</DIV>
<DIV>Karen</DIV>
<DIV>(Arup Facades)<BR><BR></DIV>
<DIV class=gmail_quote>On Mon, Sep 22, 2008 at 12:06 PM, Josh Greenfield <SPAN
dir=ltr><<A
href="mailto:JGreenfield@primerachicago.com">JGreenfield@primerachicago.com</A>></SPAN>
wrote:<BR>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<DIV lang=EN-US link="blue" vlink="purple">
<DIV>
<P>Does anyone have any rules of thumb on a quick/easy approximation for
taking a Center-of-Glass U-value and converting it to an Assembly U-value
based on industry standard assembly constructions? I know this depends
on a lot of variables, like frame material and conductance, and the size of
the overall glass assembly, etc., but I'm just looking for a quick estimate on
performance reduction for comparisons to other window types for a particular
building.</P>
<P> </P>
<P>Also, is there an ASHRAE 90.1-2004 Baseline glass Visible Light
Transmittance (VLT)?</P>
<P> </P>
<P><SPAN style="FONT-SIZE: 10pt">Josh Greenfield, <SPAN
style="FONT-SIZE: 7.5pt">PE</SPAN></SPAN><SPAN style="FONT-SIZE: 7.5pt">, LEED
AP</SPAN><SPAN style="FONT-SIZE: 10pt"><BR>Senior Associate<BR>Primera
Engineers, Ltd.<BR>100 S. Wacker Drive, Suite 700<BR>Chicago, IL
60606<BR>312.606.0910 Main<BR>312.242.6392 Direct<BR>312.606.0415
Fax<BR></SPAN><SPAN style="FONT-SIZE: 10pt"><A
title=blocked::mailto:jgreenfield@primerachicago.com><SPAN
style="COLOR: blue">jgreenfield@primerachicago.com</SPAN></A><BR><A
title=blocked::http://www.primerachicago.com/
href="http://www.primerachicago.com/" target=_blank><SPAN
style="COLOR: blue">http://www.primerachicago.com</SPAN></A></SPAN><SPAN
style="FONT-SIZE: 12pt"></SPAN></P>
<P><SPAN style="FONT-SIZE: 10pt; COLOR: green">Be Green...please consider the
environment before printing this
email.</SPAN></P></DIV></DIV><BR>_______________________________________________<BR>Bldg-sim
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clear=all><BR>-- <BR>Karen Elisabeth Mozes<BR></DIV></BODY></HTML>