<HTML dir=ltr><HEAD>
<META http-equiv=Content-Type content="text/html; charset=unicode">
<META content="MSHTML 6.00.6000.16674" name=GENERATOR></HEAD>
<BODY>
<DIV id=idOWAReplyText31729 dir=ltr>
<DIV dir=ltr><FONT face=Arial color=#000000 size=2>Evan,</FONT></DIV>
<DIV dir=ltr><FONT face=Arial size=2></FONT> </DIV>
<DIV dir=ltr><FONT face=Arial size=2>The glass panes in your examples have very different properties, namely conductivity: 0.760 vs. 1.050. ~1.000 sounds right for glass; I've seen commercial products in with ~0.800 ... 0.760 seems very low. In doubt, you should rely on LBNL's Window: <A href="http://windows.lbl.gov/software/window/window.html">http://windows.lbl.gov/software/window/window.html</A> ... or WIS (<A href="http://www.windat.org/wis/html/index.html">http://www.windat.org/wis/html/index.html</A>) which will provide you with properties for a vast number of commercially-available glass types.</FONT></DIV>
<DIV dir=ltr><FONT face=Arial size=2></FONT> </DIV>
<DIV dir=ltr><FONT face=Arial size=2>Hope this helps,</FONT></DIV>
<DIV dir=ltr><FONT face=Arial size=2>Denis</FONT></DIV></DIV>
<DIV dir=ltr><BR>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>De:</B> esp-r-bounces@lists.strath.ac.uk de la part de Evan Sterling<BR><B>Date:</B> ven. 2008-07-11 12:01<BR><B>À:</B> esp-r@lists.strath.ac.uk<BR><B>Objet :</B> [esp-r] Perplexing U-values with low-e glass<BR></FONT><BR></DIV>
<DIV>I am modelling some triple-glazed windows, by copying the default double-glazed units provided in the database and adding an extra air gap and pane (see below for details). But when I substitute low-e glass for plate glass, the U-value calculated automatically actually rises somewhat, when I would expect it to drop. Is there something I'm missing here?<BR><BR><BR><B>Normal glass</B><BR>
<P><SPAN> </SPAN>Layer|Prim|Thick |Conduc-|Density|Specif|IR<SPAN> </SPAN>|Solr|Diffu| R<SPAN> </SPAN>|Descr<SPAN> </SPAN>|db<SPAN> </SPAN>|(mm)<SPAN> </SPAN>|tivity |<SPAN> </SPAN>|heat<SPAN> </SPAN>|emis|abs |resis|m^2K/W</P>
<P><SPAN> </SPAN>Ext<SPAN> </SPAN>242<SPAN> </SPAN>6.0<SPAN> </SPAN>0.760<SPAN> </SPAN>2710.<SPAN> </SPAN>837. 0.83 0.05 19200.<SPAN> </SPAN>0.01 plate glass : Plate glass with placeholder s</P>
<P><SPAN> </SPAN>2<SPAN> </SPAN>0<SPAN> </SPAN>12.0<SPAN> </SPAN>0.000<SPAN> </SPAN>0.<SPAN> </SPAN>0. 0.99 0.99<SPAN> </SPAN>1.<SPAN> </SPAN>0.17 air<SPAN> </SPAN>0.17 0.17 0.17</P>
<P><SPAN> </SPAN>3<SPAN> </SPAN>242<SPAN> </SPAN>6.0<SPAN> </SPAN>0.760<SPAN> </SPAN>2710.<SPAN> </SPAN>837. 0.83 0.05 19200.<SPAN> </SPAN>0.01 plate glass : Plate glass with placeholder s</P>
<P><SPAN> </SPAN>4<SPAN> </SPAN>0<SPAN> </SPAN>12.0<SPAN> </SPAN>0.000<SPAN> </SPAN>0.<SPAN> </SPAN>0. 0.99 0.99<SPAN> </SPAN>1.<SPAN> </SPAN>0.17 air<SPAN> </SPAN>0.17 0.17 0.17</P>
<P><SPAN> </SPAN>Int<SPAN> </SPAN>242<SPAN> </SPAN>6.0<SPAN> </SPAN>0.760<SPAN> </SPAN>2710.<SPAN> </SPAN>837. 0.83 0.05 19200.<SPAN> </SPAN>0.01 plate glass : Plate glass with placeholder s</P>
<P><SPAN> </SPAN>ISO 6946 U values (horiz/upward/downward heat flow)=<SPAN> </SPAN><B>1.874<SPAN> </SPAN>1.985<SPAN> </SPAN>1.743</B> (partition)<SPAN> </SPAN>1.603</P><BR><BR><B>Low-E glass</B><BR>
<P><SPAN> </SPAN>Layer|Prim|Thick |Conduc-|Density|Specif|IR<SPAN> </SPAN>|Solr|Diffu| R<SPAN> </SPAN>|Descr<SPAN> </SPAN>|db<SPAN> </SPAN>|(mm)<SPAN> </SPAN>|tivity |<SPAN> </SPAN>|heat<SPAN> </SPAN>|emis|abs |resis|m^2K/W</P>
<P><SPAN> </SPAN>Ext<SPAN> </SPAN>246<SPAN> </SPAN>6.0<SPAN> </SPAN>1.050<SPAN> </SPAN>2500.<SPAN> </SPAN>750. 0.05 0.06 19200.<SPAN> </SPAN>0.01 low_e glass : 6mm CF Low_e glass with placeh</P>
<P><SPAN> </SPAN>2<SPAN> </SPAN>0<SPAN> </SPAN>12.0<SPAN> </SPAN>0.000<SPAN> </SPAN>0.<SPAN> </SPAN>0. 0.99 0.99<SPAN> </SPAN>1.<SPAN> </SPAN>0.17 air<SPAN> </SPAN>0.17 0.17 0.17</P>
<P><SPAN> </SPAN>3<SPAN> </SPAN>246<SPAN> </SPAN>6.0<SPAN> </SPAN>1.050<SPAN> </SPAN>2500.<SPAN> </SPAN>750. 0.05 0.06 19200.<SPAN> </SPAN>0.01 low_e glass : 6mm CF Low_e glass with placeh</P>
<P><SPAN> </SPAN>4<SPAN> </SPAN>0<SPAN> </SPAN>12.0<SPAN> </SPAN>0.000<SPAN> </SPAN>0.<SPAN> </SPAN>0. 0.99 0.99<SPAN> </SPAN>1.<SPAN> </SPAN>0.17 air<SPAN> </SPAN>0.17 0.17 0.17</P>
<P><SPAN> </SPAN>Int<SPAN> </SPAN>246<SPAN> </SPAN>6.0<SPAN> </SPAN>1.050<SPAN> </SPAN>2500.<SPAN> </SPAN>750. 0.05 0.06 19200.<SPAN> </SPAN>0.01 low_e glass : 6mm CF Low_e glass with placeh</P>
<P><SPAN> </SPAN>ISO 6946 U values (horiz/upward/downward heat flow)=<SPAN> </SPAN><B>1.897<SPAN> </SPAN>2.011<SPAN> </SPAN>1.763</B> (partition)<SPAN> </SPAN>1.620</P><BR>
<P></P>Thanks,<BR clear=all>Evan Sterling<BR>Mathematics & Engineering<BR>Queen's University<BR></DIV></BODY></HTML>