<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:st1="urn:schemas-microsoft-com:office:smarttags" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=ProgId content=Word.Document>
<meta name=Generator content="Microsoft Word 11">
<meta name=Originator content="Microsoft Word 11">
<link rel=File-List href="cid:filelist.xml@01CA7322.5FF7D440">
<link rel=Edit-Time-Data href="cid:editdata.mso">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]-->
<title>Re: [Bldg-sim] Why should roofs have high emissivity?</title>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="place"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="address"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="PostalCode"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="State"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="City"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="Street"/>
<!--[if gte mso 9]><xml>
<o:OfficeDocumentSettings>
<o:DoNotRelyOnCSS/>
</o:OfficeDocumentSettings>
</xml><![endif]--><!--[if gte mso 9]><xml>
<w:WordDocument>
<w:DontDisplayPageBoundaries/>
<w:DisplayBackgroundShape/>
<w:SpellingState>Clean</w:SpellingState>
<w:GrammarState>Clean</w:GrammarState>
<w:DocumentKind>DocumentEmail</w:DocumentKind>
<w:EnvelopeVis/>
<w:ValidateAgainstSchemas/>
<w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid>
<w:IgnoreMixedContent>false</w:IgnoreMixedContent>
<w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText>
<w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel>
</w:WordDocument>
</xml><![endif]--><!--[if gte mso 9]><xml>
<w:LatentStyles DefLockedState="false" LatentStyleCount="156">
</w:LatentStyles>
</xml><![endif]--><!--[if !mso]>
<style>
st1\:*{behavior:url(#default#ieooui) }
</style>
<![endif]-->
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;
mso-font-charset:0;
mso-generic-font-family:swiss;
mso-font-pitch:variable;
mso-font-signature:1627421319 -2147483648 8 0 66047 0;}
@font-face
{font-family:"Franklin Gothic Medium";
panose-1:2 11 6 3 2 1 2 2 2 4;
mso-font-charset:0;
mso-generic-font-family:swiss;
mso-font-pitch:variable;
mso-font-signature:647 0 0 0 159 0;}
@font-face
{font-family:Webdings;
panose-1:5 3 1 2 1 5 9 6 7 3;
mso-font-charset:2;
mso-generic-font-family:roman;
mso-font-pitch:variable;
mso-font-signature:0 268435456 0 0 -2147483648 0;}
@font-face
{font-family:Verdana;
panose-1:2 11 6 4 3 5 4 4 2 4;
mso-font-charset:0;
mso-generic-font-family:swiss;
mso-font-pitch:variable;
mso-font-signature:536871559 0 0 0 415 0;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{mso-style-parent:"";
margin:0in;
margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;
text-underline:single;}
a:visited, span.MsoHyperlinkFollowed
{color:blue;
text-decoration:underline;
text-underline:single;}
span.EmailStyle17
{mso-style-type:personal-reply;
mso-style-noshow:yes;
mso-ansi-font-size:10.0pt;
mso-bidi-font-size:10.0pt;
font-family:Arial;
mso-ascii-font-family:Arial;
mso-hansi-font-family:Arial;
mso-bidi-font-family:Arial;
color:navy;}
span.SpellE
{mso-style-name:"";
mso-spl-e:yes;}
span.GramE
{mso-style-name:"";
mso-gram-e:yes;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.25in 1.0in 1.25in;
mso-header-margin:.5in;
mso-footer-margin:.5in;
mso-paper-source:0;}
div.Section1
{page:Section1;}
-->
</style>
<!--[if gte mso 10]>
<style>
/* Style Definitions */
table.MsoNormalTable
{mso-style-name:"Table Normal";
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-parent:"";
mso-padding-alt:0in 5.4pt 0in 5.4pt;
mso-para-margin:0in;
mso-para-margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:10.0pt;
font-family:"Times New Roman";
mso-ansi-language:#0400;
mso-fareast-language:#0400;
mso-bidi-language:#0400;}
</style>
<![endif]-->
</head>
<body lang=EN-US link=blue vlink=blue style='tab-interval:.5in'>
<div class=Section1>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I’ll add some general info to the
discussion and do a little summing up.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>LBL has studied emissivity and reflectance
and has annual energy impact results for hot and cold climates:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><a
href="http://eetd.lbl.gov/HeatIsland/CoolRoofs/HeatTransfer/Heating.html">http://eetd.lbl.gov/HeatIsland/CoolRoofs/HeatTransfer/Heating.html</a><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The Heat Island Group has a lot of
information available pertinent to the emissivity discussion:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><a href="http://eetd.lbl.gov/HeatIsland/">http://eetd.lbl.gov/HeatIsland/</a><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>We’ve been focusing on roofs, but window
design also has to consider the same effects. For glazing, we add the property
of <span class=SpellE>transmissivity</span> (radiation passing through the
surface) and we have to get more specific about the types of radiation (solar,
visible, UV, infrared) and the direction (outside vs. inside, as well as angle
of incidence).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><a
href="http://www.commercialwindows.umn.edu/issues_energy1.php">http://www.commercialwindows.umn.edu/issues_energy1.php</a><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>For opaque building surfaces, such as
roofs, walls and window frames, it is understood that unless stated otherwise:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Reflectivity and <span class=SpellE>absorptivity</span>
values are for solar radiation.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Emissivity values are for
thermal/far-infrared radiation.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>1 – <span class=GramE>reflectivity</span>
= <span class=SpellE>absorptivity</span><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>So when ASHRAE 90.1 Table G3.1 requires
you to model a roof reflectivity of 0.30, you can use an <span class=SpellE>absorptance</span>
of 0.70 (such as when modeling in eQUEST).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>While there are technical distinctions,
the following terms are generally used interchangeably:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Reflectance/reflectivity<o:p></o:p></span></font></p>
<p class=MsoNormal><span class=SpellE><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Absorptance/absorptivity</span></font></span><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><span class=SpellE><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Emittance</span></font></span><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>/emissivity<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>~Bill<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><font size=2
color=black face="Franklin Gothic Medium"><span style='font-size:10.0pt;
font-family:"Franklin Gothic Medium";color:black;font-weight:bold;mso-bidi-font-weight:
normal;mso-no-proof:yes'>William Bishop, EIT, LEED<sup>®</sup> AP </span></font></b><b
style='mso-bidi-font-weight:normal'><font size=2 color="#006600"
face="Franklin Gothic Medium"><span style='font-size:10.0pt;font-family:"Franklin Gothic Medium";
color:#006600;font-weight:bold;mso-bidi-font-weight:normal;mso-no-proof:yes'>|</span></font></b><b
style='mso-bidi-font-weight:normal'><font size=2 color=black
face="Franklin Gothic Medium"><span style='font-size:10.0pt;font-family:"Franklin Gothic Medium";
color:black;font-weight:bold;mso-bidi-font-weight:normal;mso-no-proof:yes'> </span></font></b><b
style='mso-bidi-font-weight:normal'><font size=2 color=black
face="Franklin Gothic Medium"><span style='font-size:10.0pt;mso-bidi-font-size:
12.0pt;font-family:"Franklin Gothic Medium";color:black;font-weight:bold;
mso-bidi-font-weight:normal;mso-no-proof:yes'>Pathfinder Engineers &
Architects LLP</span></font></b><b><font size=2 color=black
face="Franklin Gothic Medium"><span style='font-size:10.0pt;font-family:"Franklin Gothic Medium";
color:black;font-weight:bold;mso-no-proof:yes'><o:p></o:p></span></font></b></p>
<p class=MsoNormal><font size=1 color=black face=Arial><span style='font-size:
9.0pt;font-family:Arial;color:black;mso-no-proof:yes'>Mechanical Engineer<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=1 color=black face=Arial><span style='font-size:
5.0pt;font-family:Arial;color:black;mso-no-proof:yes'><o:p> </o:p></span></font></p>
<p class=MsoNormal><st1:address w:st="on"><st1:Street w:st="on"><font size=1
color=navy face=Arial><span style='font-size:9.0pt;font-family:Arial;
color:navy;mso-no-proof:yes'>134 South Fitzhugh Street</span></font></st1:Street><font
size=1 color=navy><span style='font-size:9.0pt;color:navy;mso-no-proof:yes'><br>
</span></font><st1:City w:st="on"><font size=1 color=navy face=Arial><span
style='font-size:9.0pt;font-family:Arial;color:navy;mso-no-proof:yes'>Rochester</span></font></st1:City><font
size=1 color=navy face=Arial><span style='font-size:9.0pt;font-family:Arial;
color:navy;mso-no-proof:yes'>, <st1:State w:st="on">NY</st1:State> <st1:PostalCode
w:st="on">14608</st1:PostalCode></span></font></st1:address><font size=1
color=navy><span style='font-size:9.0pt;color:navy;mso-no-proof:yes'><br>
</span></font><font size=1 color=navy face=Arial><span style='font-size:9.0pt;
font-family:Arial;color:navy;mso-no-proof:yes'>T: (585) 325-6004 </span></font><font
size=1 color=black face=Arial><span style='font-size:9.0pt;font-family:Arial;
color:black;mso-no-proof:yes'>Ext. 114</span></font><font size=1 color=navy><span
style='font-size:9.0pt;color:navy;mso-no-proof:yes'><br>
</span></font><font size=1 color=navy face=Arial><span style='font-size:9.0pt;
font-family:Arial;color:navy;mso-no-proof:yes'>F: (585) 325-6005</span></font><font
size=1 color=black face=Arial><span style='font-size:9.0pt;mso-bidi-font-size:
12.0pt;font-family:Arial;color:black;mso-no-proof:yes'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=1 color=black face=Arial><span style='font-size:
9.0pt;font-family:Arial;color:black;mso-no-proof:yes'>wbishop@pathfinder-ea.com<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=1 color=black face=Arial><span style='font-size:
9.0pt;mso-bidi-font-size:12.0pt;font-family:Arial;color:black;mso-no-proof:
yes'>www.pathfinder-ea.com</span></font><font color=navy><span
style='color:navy;mso-no-proof:yes'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=5 color=green face=Webdings><span
style='font-size:18.0pt;font-family:Webdings;mso-bidi-font-family:Webdings;
color:green;mso-no-proof:yes'>P</span></font><font color=green><span
style='color:green;mso-no-proof:yes'> </span></font><font size=1 color=green><span
style='font-size:7.5pt;color:green;mso-no-proof:yes'>Please strive to live
sustainably.</span></font><font color=green><span style='color:green'><o:p></o:p></span></font></p>
</div>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
bldg-sim-bounces@lists.onebuilding.org
[mailto:bldg-sim-bounces@lists.onebuilding.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Christopher Schaffner<br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, December 02, 2009
6:48 AM<br>
<b><span style='font-weight:bold'>To:</span></b> muehleisen@iit.edu; Chris
Jones<br>
<b><span style='font-weight:bold'>Cc:</span></b> bldg-sim@lists.onebuilding.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [Bldg-sim] Why should
roofs have high emissivity?</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=2 face=Verdana><span
style='font-size:11.0pt;font-family:Verdana'>Of course, if your roof is well
insulated, it will be covered with snow. I doubt very much that your
“warm” roof will really help much. Go with the cool roof. <br>
<br>
--<br>
<br>
Chris Schaffner, PE, LEED AP, LEED Faculty™<br>
Founder and Principal<br>
<br>
The Green Engineer, LLP<br>
Sustainable Design Consulting<br>
<st1:Street w:st="on"><st1:address w:st="on">50 Beharrell Street</st1:address></st1:Street><br>
<st1:place w:st="on"><st1:City w:st="on">Concord</st1:City>, <st1:State w:st="on">MA</st1:State>
<st1:PostalCode w:st="on">01742</st1:PostalCode></st1:place><br>
T: 978.369.8978<br>
M:978.844.1464<br>
<a href="chris@greenengineer.com">chris@greenengineer.com</a><br>
www.greenengineer.com<br>
<br>
<br>
On 12/2/09 12:26 AM, "Ralph Muehleisen" <<a
href="muehleisen@gmail.com">muehleisen@gmail.com</a>> wrote:</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=2 face=Verdana><span style='font-size:11.0pt;
font-family:Verdana'>Chris makes a good point to consider with cool roofs.<br>
<br>
A cool roof will indeed reduce solar heat gain to the roof which reduces its
temp (good in summer) and reduces cooling requirements in summer but will
increase heating requirements in the winter.<br>
<br>
Until someone develops a material where the emissivity changes with temperature
(and not just wavelength) a cool roof that is good in summer will be bad in
winter.<br>
<br>
So, in colder climates, a cool roof can indeed increase the overall energy use
of a building.<br>
<br>
Even so, some northern cities like <st1:City w:st="on"><st1:place w:st="on">Chicago</st1:place></st1:City>,
mandate cool roofs in building code. Why? Because the cool roof
will reduce the urban heat island effect where the city has increased
temperatures compared to the surrounding areas. <br>
<br>
The thought is that the overall benefits of the reduction in urban heat
island effect in summer is more important than the increased energy use that
comes from increased winter cooling load.<br>
<br>
<br>
Ralph<br>
<br>
Ralph Muehleisen, Ph.D., P.E., LEED AP, FASA<br>
Assistant Professor and Director of the Miller Acoustics Lab<br>
Civil, Architectural and Environmental Engineering<br>
Illinois Institute of Technology<br>
<st1:place w:st="on"><st1:City w:st="on">Chicago</st1:City>, <st1:State w:st="on">IL</st1:State>
<st1:PostalCode w:st="on">60616</st1:PostalCode></st1:place><br>
<a href="muehleisen@iit.edu">muehleisen@iit.edu</a><br>
tel: 312-567-3545 fax:312-567-3519<br>
<br>
<br>
On Tue, Dec 1, 2009 at 6:28 PM, Chris Jones <<a href="cj@cr-jay.ca">cj@cr-jay.ca</a>>
wrote:</span></font><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=2 face=Verdana><span
style='font-size:11.0pt;font-family:Verdana'>In some cases it may be counter
productive to use a high emissivity roof. I have worked on uncooled
warehouses where the team used an approved roofing product to get that point
but the heating energy increased enough to lower the savings enough to lose an
EAc1 point. <br>
<br>
<br>
<br>
<br>
<br>
<br>
Chris Jones<br>
<st1:Street w:st="on"><st1:address w:st="on">14 Oneida Avenue</st1:address></st1:Street><br>
<st1:place w:st="on"><st1:City w:st="on">Toronto</st1:City>, <st1:State w:st="on">ON</st1:State>
<st1:PostalCode w:st="on">M5J 2E3</st1:PostalCode></st1:place>.<br>
Tel. 416-203-7465<br>
Fax. 416-946-1005<br>
<br>
<br>
_______________________________________________<br>
Bldg-sim mailing list<br>
<a href="http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org">http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org</a><br>
To unsubscribe from this mailing list send a blank message to <a
href="BLDG-SIM-UNSUBSCRIBE@ONEBUILDING.ORG">BLDG-SIM-UNSUBSCRIBE@ONEBUILDING.ORG</a></span></font><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=2 face=Verdana><span
style='font-size:11.0pt;font-family:Verdana'><o:p> </o:p></span></font></p>
<div class=MsoNormal align=center style='text-align:center'><font size=2
face=Verdana><span style='font-size:11.0pt;font-family:Verdana'>
<hr size=3 width="95%" align=center>
</span></font></div>
<p class=MsoNormal><font size=2 face=Verdana><span style='font-size:10.0pt;
font-family:Verdana'>_______________________________________________<br>
Bldg-sim mailing list<br>
<a href="http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org">http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org</a><br>
To unsubscribe from this mailing list send a blank message to <a
href="BLDG-SIM-UNSUBSCRIBE@ONEBUILDING.ORG">BLDG-SIM-UNSUBSCRIBE@ONEBUILDING.ORG</a></span></font><o:p></o:p></p>
</div>
</body>
</html>