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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Dear Bldg-Sim folk,<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 think that overdesigning / oversizing is rampant in the
engineering community. Largely, this is a response to concerns about
litigation or worries about non-technical clients who don’t know how they’ll
use a facility. VSD- equipped fans and pumps go a long way toward
reducing the energy penalty associated with oversized systems, but it can still
be severe.<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 think I’ve read recently that many systems are 50% larger
than actually required. This, of course, means that duct, pipe, and water,
gas and electrical service are also oversized and more costly than needed (not
to mention the equipment itself). I recently reviewed some load
calculations where the designer used ~5W / sq.ft. for internal loads in an office
space that was pursuing LEED certification. The same space required ~1W /
sq.f.t for lighting in order to meet the ASHRAE 90.1 requirements and had
normal plug loads, all of which probably didn’t add up to anything near
5W/sq.ft. On top of that, the zone HVAC equipment was heat pumps, so I
have serious doubts about the quality of humidity control for oversized DX
equipment.<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'>Doing the math shows that 1% of the summer hours is , well,
1%! 99% of the time, loads will be met; that’s a lot! In addition,
the 1% hours do not occur all at once; the HVAC has a chance to catch up at
night. They don’t occur at the beginning of the day, either.
Comfort is maintained for the bulk of the day in most cases and the “unmet
loads” may even occur after most occupants have gone home due to the
normal thermal lag.<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'>Early in my career, I UNDER-sized a heating system in the
Midwest and learned that I was TOO close to the capacity line, Since
then, my philosophy has been somewhere between “Make sure capacity is
plenty, with good part load performance” and “Act like an engineer
and believe your own calculations (without padding them)!” Lately,
I’m leaning more toward the second one.<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 align=center style='text-align:center'><b><span
style='font-size:13.5pt;color:#1F497D'>The Building Performance Team<br>
</span></b><b><span style='color:#1F497D'>James V. Dirkes II, P.E., LEED AP<br>
</span></b><span style='color:#1F497D'>1631 Acacia Drive NW<br>
Grand Rapids, MI 49504<br>
616 450 8653<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 style='margin-left:.5in'><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>Nick Caton<br>
<b>Sent:</b> Tuesday, June 22, 2010 12:16 PM<br>
<b>To:</b> Rob Hudson; Seth P. Spangler<br>
<b>Cc:</b> bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Bldg-sim] ASHRAE question<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'>I can confirm: I learned
during and after schooling that the choice to use any set of columns is the
designers’ preference. Some designers will flip between based on
elements of the project at hand, and others will always stick to one set of
columns based on their personal tolerance/perception of the stringency of each
set of conditions.<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:.5in'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:.5in'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'>I don’t know if ASHRAE
intended this, but personally I always use the most stringent figures as a rule
when sizing up equipment. My reasoning is I’m a young designer who
hasn’t fully grasped where less conservative criteria are acceptable, and
I choose to control the potential for oversizing via final “rule-of-thumb”
/ comparative design checks and the occasional investigative energy model.<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:.5in'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:.5in'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'>~Nick<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:.5in'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:.5in'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><img width=119 height=37
id="Picture_x0020_1" src="cid:image001.jpg@01CB120B.9259F3E0"
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 style='margin-left:.5in'><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 style='margin-left:.5in'><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 style='margin-left:.5in'><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 style='margin-left:.5in'><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 style='margin-left:.5in'><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 style='margin-left:.5in'><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 style='margin-left:.5in'><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 style='margin-left:.5in'><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>
<p class=MsoNormal style='margin-left:.5in'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal style='margin-left:.5in'><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>Rob Hudson<br>
<b>Sent:</b> Tuesday, June 22, 2010 10:29 AM<br>
<b>To:</b> Seth P. Spangler<br>
<b>Cc:</b> bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Bldg-sim] ASHRAE question<o:p></o:p></span></p>
</div>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
12.0pt;margin-left:.5in'>My original response to the question was it was
designers preference. This seems to be not entirely wrong, as it could be
clients preference or space use that has some influence on the designers choice
of design conditions. Thanks for you input.<o:p></o:p></p>
<div>
<p class=MsoNormal style='margin-left:.5in'>On Tue, Jun 22, 2010 at 11:29 AM,
Seth P. Spangler <<a href="mailto:sspangle@rmf.com">sspangle@rmf.com</a>>
wrote:<o:p></o:p></p>
<div>
<div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;color:#0070C0'>Rob,</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;color:#0070C0'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;color:#0070C0'>I have never
read specific conditions of when to use one over the other however typically
the conditions used are dictated by the type of building. In my experience
buildings with low tolerances for temperature change use the 99.6%/0.4%. These
buildings would include hospitals, laboratories, R&D etc. Buildings with a
high level of tolerance will use 99%/1%. These buildings are typically office
buildings, higher education, retail etc.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;color:#0070C0'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;color:#0070C0'>In the past six
months I have seen a huge change in design conditions. The latest owner has
specified design conditions of ASHRAE 99%/1% with Summer indoor of 78 deg
F/50%RH and Winter indoor of 68 deg F. However, they want the thermostat set
point to be 73 deg F year round.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;color:#0070C0'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;font-family:"Georgia","serif";
color:#0070C0'>Seth Spangler, LEED® AP </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-family:"Georgia","serif";color:#0070C0'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;font-family:"Georgia","serif";
color:#0070C0'>RMF Engineering, Inc </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;font-family:"Georgia","serif";
color:#0070C0'>Ph: (843) 971-9639 ext:1497</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;font-family:"Georgia","serif";
color:#0070C0'>Fax: (843) 971-9641 </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;font-family:"Georgia","serif";
color:#0070C0'><a href="mailto:sspangle@rmf.com" target="_blank">sspangle@rmf.com</a></span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:10.0pt;color:#0070C0'> </span><o:p></o:p></p>
<div style='border:none;border-top:solid windowtext 1.0pt;padding:3.0pt 0in 0in 0in;
border-color:-moz-use-text-color -moz-use-text-color'>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><b><span style='font-size:10.0pt'>From:</span></b><span
style='font-size:10.0pt'> <a
href="mailto:bldg-sim-bounces@lists.onebuilding.org" target="_blank">bldg-sim-bounces@lists.onebuilding.org</a>
[mailto:<a href="mailto:bldg-sim-bounces@lists.onebuilding.org" target="_blank">bldg-sim-bounces@lists.onebuilding.org</a>]
<b>On Behalf Of </b>Rob Hudson<br>
<b>Sent:</b> Tuesday, June 22, 2010 11:15 AM<br>
<b>To:</b> <a href="mailto:bldg-sim@lists.onebuilding.org" target="_blank">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> [Bldg-sim] ASHRAE question</span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'> <o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'>I was asked what influences an engineers decision over design
conditions, and after looking for some textural support in the books, i could
not find anything to give guidance over when to use 0.4/1/2 or 99/99.6 % design
conditions. Does anyone know if this text exists in the ASHRAE books and
if so which chapter? I also looked into ASHRAE 90.1, but that only
addresses efficiencies of equipment and not the design conditions/capacity calculations.<br>
<br>
Thanks in advance,<br clear=all>
<br>
-- <br>
Rob Hudson<o:p></o:p></p>
</div>
</div>
</div>
</div>
<p class=MsoNormal style='margin-left:.5in'><br>
<br clear=all>
<br>
-- <br>
Rob Hudson<o:p></o:p></p>
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