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<div class=Section1>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Peter, Marques et al:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Thank you so much for sharing your collective insights! My
initial comments were intended only to open the discussion, as I have heard
contrarian opinions in the past and didn’t want a friend to be unaware of
them =). Consider me an interested student, certainly not an authority on the
subject!<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I for one have been motivated by this discussion to do some
homework, and now have a much better grasp of the fundamentals. Apparently ASHRAE
Journal put out a good primer roughly a year ago for others in the same boat of
curiosity to understand the concepts and challenges present in DSF design better
– I found this handy: <a
href="http://www.rwdi.com/cms/publications/76/200904_Ventilating_Facades.pdf">http://www.rwdi.com/cms/publications/76/200904_Ventilating_Facades.pdf</a><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Thanks again,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>~Nick<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><img border=0 width=119 height=37 id="Picture_x0020_1"
src="cid:image001.jpg@01CB8246.57FB26F0" alt="cid:489575314@22072009-0ABB"></span><b><span
style='font-size:11.0pt;font-family:"Stylus BT","sans-serif";color:#2D4D5E'><o:p></o:p></span></b></p>
<p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Stylus BT","sans-serif";
color:#2D4D5E'><o:p> </o:p></span></b></p>
<p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Stylus BT","sans-serif";
color:#2D4D5E'>NICK CATON, E.I.T.</span></b><b><span style='font-family:"Stylus BT","sans-serif";
color:#2D4D5E'><o:p></o:p></span></b></p>
<p class=MsoNormal><span style='font-size:7.5pt;font-family:"Calibri","sans-serif";
color:#CC9900'>PROJECT ENGINEER</span><span style='font-size:7.5pt;color:#CC9900'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>25501 west valley parkway<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>olathe ks 66061<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>direct 913 344.0036<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>fax 913 345.0617<o:p></o:p></span></p>
<p class=MsoNormal><i><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>Check out our new web-site @ </span></i><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><a
href="www.smithboucher.com" title="blocked::www.smithboucher.com"><span
style='font-size:10.0pt'>www.smithboucher.com</span></a></span><u><span
style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:blue'> </span></u><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:
"Tahoma","sans-serif";color:windowtext'> Marques da Silva [mailto:fms@lnec.pt] <br>
<b>Sent:</b> Friday, November 12, 2010 3:32 AM<br>
<b>To:</b> Peter Simmonds<br>
<b>Cc:</b> Nick Caton; Sami, Vikram; bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Bldg-sim] Is there a quick model for double skins facades?<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Hi Peter <br>
<br>
I think you are only considering DSF gap forced ventilation (<i>when the air
system was switched off after occupation?</i>). This not an issue is it's
naturally ventilated. My opinion, and I am not a designer but I've been
monitoring a few occupied DSF façades in the warm climate of Lisbon, is that as
for any other building system it has to be properly designed having in mind
location and use. I monitored really bad façades but also façades that behave
quite well allowing the interior temperature to remain within comfort levels
during weekends when HVAC is switched off.<br>
I don't know ROOM but TRNSYS is a good option for modelling DSF (see the work
of Haase et al).<br>
I agree that cold climates are preferable when considering a DSF option, but
there are other issues like, for example, tall and wind exposed façades,
specially if glazzed, where inside shading is thermally a bad option and
for outside positioning fast damage is certain. Anyway owners may allways impose
a look for their building...<br>
<br>
<o:p></o:p></p>
<div>
<p>Nick and Vikram, double skin facades or climate walls or windows have been
around for many years now. Vikram's question is really how do you produce a
back of the envelope calculation to see if a double skin façade is a viable
option. Well here goes, the basic improvement by using a double façade is the
improvement of the U value decreasing energy loss. Take a look around the world
and the successful applications of double facades is mostly in regions where
heating is the dominant energy consumer. One of the first things were learnt
more than 30 years ago was the U value was improved so long as air was
ventilated through the cavity, but what happened to the U value when the air
system was switched off after occupation? which consumed more energy, the
energy loss of the building without the function of the double façade or the
energy consumption of the air system to maintain the functionality of the
double façade. Beyond the improvement of the U value we can then start looking
at improved shading coefficients and surface temperature control of the inside
surface of the double façade. For these different aspects of double façade
design I believe the design criteria was simplified in a series of tables
issued in a couple of ISSO publications in the 80's. These documents will get
you rough data to be able to assess whether or not the double façade is
feasible. As far as deluxe simulation tools probably the best is the ROOM
program by Mike Holmes and Andrew White and then there is also TRNSYS. <o:p></o:p></p>
<p>Getting back to Nick's comments, I have found over the years that the most
comments regarding double facades come from people that have never designed
them, here I am referring to the article and not you Nick. <o:p></o:p></p>
<p>I first started designing double facades in the late 70's in the Netherlands
and over the years have designed quite few and completed quite a few repair
jobs on attempted double facades. One thing I have learned is that if it isn't
cold then the double façade is there for show only! <o:p></o:p></p>
<p> <o:p></o:p></p>
<div>
<div>
<p><b>Peter Simmonds, Ph.D. </b><br>
<b>Senior Associate<br>
Head of the Advanced Technology Group<br>
IBE Consulting Engineers</b><br>
<b>14130 Riverside Drive, Suite 201</b><br>
<b>Sherman Oaks, CA 91423 <br>
p: (818) 377-8220 x246 m: (818) 219-1284 f: (818) 377-8230<br>
<br>
<a href="http://www.ibece.com/" title="http://www.ibece.com/">www.ibece.com</a><br>
<i>Ideas for the built environment</i></b> <o:p></o:p></p>
</div>
</div>
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<div>
<div>
<p><b>From:</b> Nick Caton [<a href="mailto:ncaton@smithboucher.com">mailto:ncaton@smithboucher.com</a>]
<br>
<b>Sent:</b> Thursday, November 11, 2010 8:11 AM<br>
<b>To:</b> Sami, Vikram; <a href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> Re: [Bldg-sim] Is there a quick model for double skins facades?
<o:p></o:p></p>
</div>
</div>
<p> <o:p></o:p></p>
<p>Hi Vik, <o:p></o:p></p>
<p> <o:p></o:p></p>
<p>I hate to trample over anyone’s little flower patch, but I’ve
read some scathing assessments of double-facades as an energy-saving
strategy. You might want to check this and the associated references out:
<a
href="http://www.buildingscience.com/documents/insights/bsi-007-prioritizing-green-it-s-the-energy-stupid">http://www.buildingscience.com/documents/insights/bsi-007-prioritizing-green-it-s-the-energy-stupid</a>.
<o:p></o:p></p>
<p> <o:p></o:p></p>
<p>That said you might not be satisfied until you develop your own conclusions.
Proponents of this approach repeatedly cite benefits of CFD, so to give a
“fair/proper” assessment any tool you work with would probably need
to be modeling convective airflows between floors. <o:p></o:p></p>
<p> <o:p></o:p></p>
<p>~Nick <o:p></o:p></p>
<p> <o:p></o:p></p>
<div>
<p><img border=0 width=119 height=37 id="_x0000_i1025"
src="cid:image001.jpg@01CB8246.57FB26F0" alt="cid:489575314@22072009-0ABB"><o:p></o:p></p>
<p><b> </b><o:p></o:p></p>
<p><b>NICK CATON, E.I.T. </b><o:p></o:p></p>
<p>PROJECT ENGINEER <o:p></o:p></p>
<p>25501 west valley parkway <o:p></o:p></p>
<p>olathe ks 66061 <o:p></o:p></p>
<p>direct 913 344.0036 <o:p></o:p></p>
<p>fax 913 345.0617 <o:p></o:p></p>
<p><i>Check out our new web-site @ </i><a href="www.smithboucher.com"
title="blocked::www.smithboucher.com">www.smithboucher.com</a> <o:p></o:p></p>
</div>
<p> <o:p></o:p></p>
<div>
<div>
<p><b>From:</b> <a href="mailto:bldg-sim-bounces@lists.onebuilding.org">bldg-sim-bounces@lists.onebuilding.org</a>
[<a href="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</a>]
<b>On Behalf Of </b>Sami, Vikram<br>
<b>Sent:</b> Thursday, November 11, 2010 8:59 AM<br>
<b>To:</b> <a href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> [Bldg-sim] Is there a quick model for double skins facades? <o:p></o:p></p>
</div>
</div>
<p> <o:p></o:p></p>
<p>We are doing a project in a pretty cold climate. The project design has a
really big glass façade facing south. One of the ideas to reduce conductive heat
loss is to create a double skin façade on the south side. <o:p></o:p></p>
<p> <o:p></o:p></p>
<p>Now I realize that this is going to take a fair amount of analysis work to
design it properly. What I was wondering is if there is a quick analysis
tool/methodology to tell if this is even feasible to go into more detailed
analysis. <o:p></o:p></p>
<p> <o:p></o:p></p>
<p>Any help would be much appreciated <o:p></o:p></p>
<p> <o:p></o:p></p>
<p><b>Vikram Sami</b>, LEED AP <o:p></o:p></p>
<p>Sustainable Design Analyst <o:p></o:p></p>
<p>1382 Peachtree St. NE, Atlanta, GA 30309 <o:p></o:p></p>
<p>t: 404-443-7462 f: <span lang=ES>404.892.5823 </span>
e: <a href="mailto:vikram.sami@perkinswill.com">vikram.sami@perkinswill.com</a>
<a href="http://www.perkinswill.com/">www.perkinswill.com</a> <o:p></o:p></p>
<p><b>Perkins+Will.</b> Ideas + buildings that honor the broader goals of
society <o:p></o:p></p>
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