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in reality, i would agree with you. if you were attempting to compare
energy simulations for two different types of systems and were
comparing the difference in outdoor air loads on system size/capacity
(and costs of different systems) using the minimum per the different
system types would be beneficial.<br>
<br>
in leedality though the approach is a little different. 90.1 app g
requires the minimum outdoor ventilation be the same to help prevent
gaming the energy simulations, and is "enforced" by the leed reviewer's
commenting on it. the outdoor ventilation rate is the minimum
designed outdoor ventilation rate. so if the design is for a DOAS
system then the minimum outdoor air rate for that system type is to be
used in the baseline system. same as if it the design were a packaged
system but the baseline were VAV based on SF of the building (it
happens) - the minimum oa rate would be what is designed for the
packaged system.<br>
<br>
except for the exception noted on page 182 when using dcv in the
proposed if it is not required in the baseline.<br>
<br>
look in the user's manual on page g-26, right column in the 1st
ventilation paragraph, "outdoor air ventilation can be a major
contributor to building energy consumption, but i is not considered an
opportunity for energy savings under the performance rating method.
the minimum ventilation rates designed for the proposed building (not
counting extra ventilation for economizer cooling) must also be modeled
the same in both the baseline building and the proposed building."<br>
<br>
in other words, in order to comply with the energy simulation
requirements of 90.1 appendix g (the performance rating method) the
minimum outdoor air rate has to be the same in both the proposed and
baseline energy simulations (models). so yes, outside of the one
exception for dcv systems, the baseline outdoor air rate is the same as
the proposed if you are only providing the minimum required per ashrae
62 regardless of what system type the baseline building is required to
use.<br>
<br>
On 8/18/11 7:47 AM, Michael A. Eustice wrote:
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<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">Unless
I’m misunderstanding something, your sentence:
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color: black;">‘</span>when would
the baseline be the same? when you only provide the minimum required
outside air per ashrae 62.’
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">Seems
untrue to me. Just so everyone is clear, under exact same conditions
(occupancy, sqft, bldg type etc.), with the only difference being
system type (VAV versus DOAS), the minimum required ventilation cfm
required by ASHRAE 62.1 will be different. The VAV system will almost
always demand a higher minimum ventilation cfm, sometimes significantly
more, since one zone can drive the system towards 100% outside air.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">Michael</span><span
style="color: rgb(31, 73, 125);"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<div>
<div
style="border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">From:</span></b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">
<a class="moz-txt-link-abbreviated" href="mailto:bldg-sim-bounces@lists.onebuilding.org">bldg-sim-bounces@lists.onebuilding.org</a>
[<a class="moz-txt-link-freetext" href="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</a>]
<b>On Behalf Of </b>Patrick J. O'Leary, Jr.<br>
<b>Sent:</b> Thursday, August 18, 2011 10:33 AM<br>
<b>To:</b> Anne Juran<br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> Re: [Bldg-sim] DOAS and baseline OA<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">note that 90.1 requires the
<i>minimum</i> outdoor ventilation rates be the same in
both the proposed and baseline models. this is to prevent gaming of
the baseline system sizes by adding capacity/increasing unit sizes
which will increase baseline energy cost. <br>
<br>
though the baseline ventilation rate(s) can be the same or less than
the proposed they can't be more.
<br>
<br>
when would the baseline be the same? when you only provide the minimum
required outside air per ashrae 62.
<br>
<br>
when would they be different? when you provide more outside air in the
proposed design than is required by ashrae 62.
<br>
e.g.1 providing 30% more outdoor air than required to obtain 1 leed
point via ieqc2 (increased ventilation) (or using the international
mechanical code ventilation rates if your local jurisdiction does not
accept ashrae 62)<br>
e.g.2 using evap cooling systems sized on air change rate by volume
& 100% outdoor air. ashrae 62 may require only 2,000 cfm but if
you provide 20,000 cfm (based on space volume) then the proposed would
have 20,000 cfm outdoor air and the baseline would have 2,000 cfm. in
a case such as this using 20,000 cfm in the baseline would require a
very oversized unit that would use a lot more energy to condition the
outdoor air and would reward you with more points under eac1/eap2.<br>
<br>
On 8/18/11 7:03 AM, Anne Juran wrote: <o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";">I
agree that the OA difference is extreme… I just let Trace run wild and
do the calculation so I’m sure I have some crazy factors that would be
adjusted for a “real” design. In retrospect, I should have looked at
it closer BEFORE submitting to USGBC. I’m sure it made them closer at
it, whereas if I was only slightly different they may have not
questioned it. Lesson learned!</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";">It
doesn’t look like I’ll get anywhere with USGBC, though, as the reviewer
explicitly stated, “the total minimum outdoor air ventilation volume in
the Baseline model must never be greater than the Proposed model.”</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";">Thanks
for all the input!</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";"> </span><o:p></o:p></p>
<div>
<div
style="border-style: solid none none; border-color: -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">From:</span></b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">
<a moz-do-not-send="true"
href="mailto:bldg-sim-bounces@lists.onebuilding.org">bldg-sim-bounces@lists.onebuilding.org</a>
[<a moz-do-not-send="true"
href="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</a>]
<b>On Behalf Of </b>Jeremy Poling<br>
<b>Sent:</b> Thursday, August 18, 2011 9:40 AM<br>
<b>To:</b> <a moz-do-not-send="true"
href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> Re: [Bldg-sim] DOAS and baseline OA</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">While I
don’t intend to discuss the merits of VAV systems and know I’m part of
a minority in that area, this is exactly why DOAS systems are being
explored more right now on the research side (take for example the
number of ASHRAE Journal articles on the topic over the past few
years). Without seeing your OA calcs I would also agree that the
difference is more than I would expect between the two systems, but I’m
more inclined to think the DOAS might be a bit low if it is being used
in conjunction with FCUs. VAV systems are typically underventilated
due to two common mistakes in the calculations: not analyzing with the
correct Ez and not using the minimum expected primary airflow for
design purposes (refer to ASHRAE 62.1-2007 Section 6.2.5.1,
specifically the note in that section). When fixing these two typical
mistakes in calculations without optimizing the primary airflow rates,
I typically see OA requirements double from the incorrectly calculated
values.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">This
situation is a good example of when to do one of two things (possibly
both together)</span><o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><span
style="color: rgb(31, 73, 125);">If this is a LEED project, submit a
project-specific CIR</span><o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent: -0.25in;"><span
style="color: rgb(31, 73, 125);">Use section ASHRAE 90.1-2007 Section
2.5 Exceptional Calculation Methodology to get around the requirement
and document the energy savings from reduced OA requirements for a DOAS
system.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"> </span><o:p></o:p></p>
<div>
<p class="MsoNormal" style="margin-bottom: 12pt;"><b><span
style="font-size: 7.5pt; font-family: "Verdana","sans-serif"; color: rgb(31, 73, 125);">Jeremy
R. Poling, PE, LEED AP+BDC</span></b><o:p></o:p></p>
</div>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"> </span><o:p></o:p></p>
<div>
<div
style="border-style: solid none none; border-color: -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">From:</span></b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">
<a moz-do-not-send="true"
href="mailto:bldg-sim-bounces@lists.onebuilding.org">bldg-sim-bounces@lists.onebuilding.org</a>
[<a moz-do-not-send="true"
href="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</a>]
<b>On Behalf Of </b>Mark Sorensen<br>
<b>Sent:</b> Wednesday, August 17, 2011 11:42 AM<br>
<b>To:</b> <a moz-do-not-send="true"
href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> Re: [Bldg-sim] DOAS and baseline OA</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Anne,<br>
<br>
While LEED/ASHRAE 90.1 requires the ventilation rates to be the same in
both the Baseline and Proposed systems, the calculated difference for
the two systems is much higher than expected. Suggest taking another
look at the calculations and confirming that the critical zone for the
VAV system has been properly determined and whether appropriate factors
for the zone air distribution effectiveness (Ez) and system ventilation
efficiency (Ev) have been applied.<br>
<br>
Mark Sorensen<br>
Diversified Energy Services<br>
Fruitport, Michigan<br>
231-578-1264<br>
<br>
On 8/16/2011 9:12 AM, Jim Dirkes wrote: <o:p></o:p></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">Dear Anne,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">I’m not
sure why you think the OA requirement varies by system. I’m not well
versed in Standard 62, but my basic understanding is that one of the
calculation methods is the result of building area and number of
occupants. Those are unchanged by system selection … which is why it
makes sense for Appendix G to require matching volumes.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"> </span><o:p></o:p></p>
<div>
<p class="MsoNormal" style="text-align: center;" align="center"><b><span
style="font-size: 13.5pt; color: rgb(31, 73, 125);">The Building
Performance Team<br>
</span></b><b><span style="color: rgb(31, 73, 125);">James V. Dirkes
II, P.E., BEMP , LEED AP<br>
</span></b><span style="color: rgb(31, 73, 125);">1631 Acacia Drive NW<br>
Grand Rapids, MI 49504<br>
616 450 8653</span><o:p></o:p></p>
</div>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"> </span><o:p></o:p></p>
<div>
<div
style="border-style: solid none none; border-color: -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif";">From:</span></b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif";">
<a moz-do-not-send="true"
href="mailto:bldg-sim-bounces@lists.onebuilding.org">bldg-sim-bounces@lists.onebuilding.org</a>
[<a moz-do-not-send="true"
href="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</a>]
<b>On Behalf Of </b>Anne Juran<br>
<b>Sent:</b> Tuesday, August 16, 2011 8:33 AM<br>
<b>To:</b> <a moz-do-not-send="true"
href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> [Bldg-sim] DOAS and baseline OA</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";">I’m
curious how everyone is handling the OA for Appendix G simulations when
using a DOAS in the proposed system. We have a design that is DOAS +
FCU with a total OA of 8,000 CFM. When you run the OA calcs for this
same building with a VAV system (the baseline), the total OA required
to meet Standard 62 is 39,000 CFM. This difference in OA represents a
significant energy savings (in climate zone 4A), yet Appendix G
requires the OA volumes to match. It does not seem “fair” to me that
the proposed case cannot take credit for design choice when it comes to
OA. I feel like Appendix G should make an exception for DOAS. Am I
missing something? Is there a way around this? Any thoughts are
appreciated!</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";">Anne</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size: 12pt; font-family: "Times New Roman","serif";"> </span><o:p></o:p></p>
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