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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Unless you are looking at very small spaces, I just don’t see
the extra volume being added to the space as introducing that significant of an
inaccuracy to the model compared to all of the other approximations,
estimations, and outright guesses we have to make to construct an energy model.<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'>Just think of any wall that is a curved surface that most
programs have to approximate as a series of planar surfaces. You can’t
perfectly match the proper volume there either.<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-family:"Franklin Gothic Demi","sans-serif";
color:#1F497D'>Nathan Miller</span><span style='color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><i><span style='font-size:10.0pt;color:#1F497D'>Senior
Energy Engineer/Mechanical Engineer<o:p></o:p></span></i></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'>direct:
206.788.4577<o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'>fax:
206.285.7111 </span><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"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> bldg-sim-bounces@lists.onebuilding.org
[mailto:bldg-sim-bounces@lists.onebuilding.org] <b>On Behalf Of </b>Chip
Barnaby<br>
<b>Sent:</b> Friday, September 11, 2009 10:37 AM<br>
<b>To:</b> Nick Caton; Ryan Del Balso; bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Bldg-sim] Where should you choose your wall location
forsimulations, inside, outside or center of wall<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>All,<br>
<br>
I generally agree with Nick's approach. I said the same thing in the
ASHRAE HOF Residential Loads chapter (which I revised in 2005). For
residences, this scheme reconciles with US practice for determining floor area
(a nominal 1000 ft2 house is 1000 ft2 only if you include the exterior wall
thickness) -- that makes it easy to check input.<br>
<br>
Volume is overstated, as noted, but generally only minimally. I've also
seen procedures for doing blower door leakage tests that recommend estimating
volume from outside dimensions.<br>
<br>
All in all, then, the outside dimension method is simple to apply consistently,
easy to check, and accurate enough.<br>
<br>
On the other hand, it does NOT agree with other standards and procedures that
are in use. There is an ASTM standard that defines floor area (I think)
and uses inside dimensions. Also, I think rentable space is sometimes
measured from the window inside surface (which I guess is the real estate
version of split the difference?).<br>
<br>
As automated data exchange procedures become more ubiquitous, definitions like
this will have to be rigorously standardized so building model fidelity can be
retained as data is passed among applications. There is an ASHRAE project
getting underway related to consistent extraction of a thermal model from a
BIM. That is a step.<br>
<br>
Chip Barnaby<br>
<br>
At 01:14 PM 9/11/2009, Nick Caton wrote:<br>
<br>
<o:p></o:p></p>
<p class=MsoNormal>Content-class: urn:content-classes:message<br>
Content-Type: multipart/related; type="multipart/alternative";<br>
boundary="----_=_NextPart_001_01CA3303.5E089D7A"<br>
<br>
My practice with all load calculation/energy modeling software has been:<br>
<br>
All floors/roofs: Top of surface<br>
Exterior glazing/walls: Outermost surface<br>
Interior walls/partitions: Center of construction<br>
<br>
I know this is the advice offered by IES-VE’s support staff, but that doesn’t
mean all modeling engines behave the same. As you may gather, I’ve always
assumed energy modeling and HVAC load calculation models “subtract out” the
thickness of constructions from calculated space volumes. I don’t know
whether this is a “universal standard practice” between software packages /
modeling engines.<br>
<br>
Since I would ultimately much rather slightly oversize than undersize an HVAC
system, I’m of the mindset that the potential for a little extra surface area /
conditioned space would if anything bump my results in a desired, conservative
direction regarding space loads. If absolute accuracy is your goal, then
in lieu of a “universal standard,” I’d imagine you would have to ask the
developers/users of the specific program you’re using at the moment to
determine its true behavior in this regard.<br>
<br>
~Nick<br>
<br>
<img width=119 height=37 id="_x0000_i1025"
src="cid:image001.jpg@01CA32CD.0FB5FD30" alt="cid:489575314@22072009-0ABB"><br>
<b> <br>
NICK CATON, E.I.T.<br>
</b>PROJECT ENGINEER<br>
25501 west valley parkway<br>
olathe ks 66061<br>
direct 913 344.0036<br>
fax 913 345.0617<br>
<i>Check out our new web-site @ </i><a href="www.smithboucher.htm">www.smithboucher.com</a><u>
<br>
</u> <br>
<b>From:</b> bldg-sim-bounces@lists.onebuilding.org [<a
href="mailto:bldg-sim-bounces@lists.onebuilding.org">
mailto:bldg-sim-bounces@lists.onebuilding.org</a>] <b>On Behalf Of </b>Ryan Del
Balso<br>
<b>Sent:</b> Friday, September 11, 2009 11:50 AM<br>
<b>To:</b> bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> [Bldg-sim] Where should you choose your wall location
forsimulations, inside, outside or center of wall<br>
<br>
Are there standard practice recommendations for where to place your wall for a
simulation? Knowing every wall has thickness, but the simulation engines
are generally just using no thickness walls with a calculated U/R value, where
should you define your walls for the simulation? Should they be defined
at the exterior face of the wall, the interior face or the center of the
wall. It seems the exterior face can greatly increase the zone volume,
thus incorrectly determining the energy usage, but the interior face
underestimates the exterior exposure of the wall. The center of wall
seems a good compromise, but is difficult to identify and draw. <br>
<br>
For interior walls/zone delineation the same question applies. >From an
energy standpoint is it better to place the zone boundary on the face of the
higher load zone or the lower load zone or split the difference?<br>
Thanks for any advice or direction to standard practices.<br>
<br>
<br>
<img border=0 width=252 height=97 id="_x0000_i1026"
src="cid:7.1.0.9.0.20090911131745.070a4af8@wrightsoft.com.3"
alt="154683_logo_final"><br>
<br>
<b>Ryan Del Balso<br>
Building Performance Engineer II<br>
ryan@ambient-e.com<br>
130 W. 5th Avenue, Denver, CO 80204 <br>
t 303.278.1532x210 | f 303.278.8533 |<br>
<a href="http://www.ambient-e.com/">ambient-e.com</a><br>
<br>
<br>
<br>
</b> <br>
<br>
<br>
<br>
<br>
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<p>---------------------------------------------------------<br>
Chip
Barnaby
cbarnaby@wrightsoft.com<br>
Vice President of Research<br>
Wrightsoft
Corp.
781-862-8719 x118 voice<br>
131 Hartwell
Ave
781-861-2058 fax<br>
Lexington, MA 02421 <a
href="http://www.wrightsoft.com/">www.wrightsoft.com<br>
</a>---------------------------------------------------------<o:p></o:p></p>
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