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<P><FONT SIZE=2>We have successfully taken credit for reduced OSA rates in a number of applications where a "cascading" make-up air system has been designed. In a kitchen hood application for instance, the traditional design might bring in 100% OSA to offset the hood exhaust from a separate intake or unit. In certain projects (schools come to mind), this make-up air can be transferred into the space via adjacent spaces with high OSA requirements (i.e. commons), thus saving all or a portion of the mechanical energy to heat/cool this air. We have always taken the path of the exceptional calculation for LEED purposes because this is definitely a grey area as far as Appendix G is concerned.<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: bldg-sim-bounces@lists.onebuilding.org on behalf of Mitchell Dec<BR>
Sent: Fri 11/7/2008 1:50 PM<BR>
To: Paul Riemer; Brandon Nichols; Michael Tillou<BR>
Cc: bldg-sim@lists.onebuilding.org<BR>
Subject: Re: [Bldg-sim] Exhaust, outside air and infiltration for LEED<BR>
<BR>
Bill, Paul, Mike, et al -<BR>
<BR>
<BR>
<BR>
We also have not mentioned another item relative to Appendix G, which<BR>
requires sizing the flow rate based on a 20-degree delta T. If the<BR>
system is a 100% OSA unit, and the baseline is sized for a 20-degree<BR>
space-to-coil temperature differential, what happens if the makeup air<BR>
unit is not designed with a 20-degree delta-T? Then it is possible the<BR>
peak CFM rates could potentially vary. So right there, we could<BR>
potentially have a contradiction between 2 lines in Appendix G - (1) OSA<BR>
ventilation rates are to be identical, and (2) The baseline AHU flow<BR>
rate is specified by a 20-degree delta T - now, which statement in<BR>
Appendix G "over rules" the other?<BR>
<BR>
<BR>
<BR>
This seems like this should fall under the Exceptional Calculation<BR>
methodology to explicitly document where the savings come from, and<BR>
whether the savings are justified...<BR>
<BR>
<BR>
<BR>
Also regarding an earlier item from this thread, that one cannot take<BR>
credit for UFAD and displacement ventilation systems with reduced CFM<BR>
rates - as long as the OSA CFM rates are identical, then credit can be<BR>
taken from the UFAD/DV system design. You'll be providing the same OSA,<BR>
but different Total CFM rates could be calculated based on the different<BR>
mixed air temperatures and designed coil leaving temperatures. This can<BR>
be either a positive or negative, which truly depends on the climate and<BR>
the ability to maximize the economizer hours...<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
Mitch Dec<BR>
Senior Energy Analyst, EIT<BR>
<BR>
LEED(r) Accredited Professional<BR>
<BR>
<BR>
<BR>
<BR>
<<A HREF="http://www.glumac.com/">http://www.glumac.com/</A>><BR>
<BR>
________________________________<BR>
<BR>
320 SW Washington, Suite 200<BR>
Portland, OR 97204-2640<BR>
T. 503.227.5280 F. 503.274.7674<BR>
<BR>
Thinking. Inside the building.<BR>
www.glumac.com <<A HREF="http://www.glumac.com/">http://www.glumac.com/</A>> <BR>
<<A HREF="http://www.glumac.com/">http://www.glumac.com/</A>><BR>
<BR>
<BR>
<BR>
<BR>
<BR>
From: bldg-sim-bounces@lists.onebuilding.org<BR>
[<A HREF="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</A>] On Behalf Of Paul Riemer<BR>
Sent: Friday, November 07, 2008 1:37 PM<BR>
To: 'Brandon Nichols'; Michael Tillou<BR>
Cc: bldg-sim@lists.onebuilding.org<BR>
Subject: Re: [Bldg-sim] Exhaust, outside air and infiltration for LEED<BR>
<BR>
<BR>
<BR>
Bill,<BR>
<BR>
This is a fascinating convergence of issues. <BR>
<BR>
<BR>
<BR>
Appendix G's requirement for the same minimum ventilation rate in the<BR>
baseline as the proposed is true but also a bit incomplete when<BR>
considering a design of a 100% OA VAV systems serving fume hoods.<BR>
<BR>
<BR>
<BR>
We have a similar scenario of a small building with likely VAV hoods,<BR>
possibly lower flow, likely served by a 100% outside air system BUT with<BR>
my favorite added complexity of district heating and cooling. <BR>
<BR>
<BR>
<BR>
Alas, while I was scratching my head, the client abandoned their LEED<BR>
goal.<BR>
<BR>
<BR>
<BR>
So I have not fully solved it for myself and cannot solve for it your<BR>
project but I do suggest the following actions:<BR>
<BR>
1) Read the 90.1-2004 prescriptive requirements for certain systems<BR>
serving fume hoods to be VAV or have heat recovery. <BR>
<BR>
2) Read the 90.1-2004 Appendix G base system selection section<BR>
<BR>
3) Now read those same sections in 90.1-2007 and ponder which changes<BR>
represent revisions and which ones represent clarifications of original<BR>
intent<BR>
<BR>
4) And maybe read the User's Manuals too<BR>
<BR>
5) Consider the exceptional calculation method as the venue to claim<BR>
energy savings, that you consider real but are not explicitly allowed or<BR>
defined by the document, for consideration by the LEED reviewer<BR>
<BR>
6) Research the existing CIR's<BR>
<BR>
7) Before spending numerous hours on an approach that may or may not be<BR>
accepted, buy a CIR and propose your tact to the USGBC itself. If they<BR>
reject yours they almost certainly will dictate a new tact that their<BR>
reviewer would be obligated to accept for your project.<BR>
<BR>
<BR>
<BR>
And lastly, do not wade too much further through this on a Friday<BR>
afternoon unless you have to do so. For me, tasks like this should be<BR>
tackled early in the day and early in the week.<BR>
<BR>
<BR>
<BR>
Good luck,<BR>
<BR>
<BR>
<BR>
Paul<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
________________________________<BR>
<BR>
From: bldg-sim-bounces@lists.onebuilding.org<BR>
[<A HREF="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</A>] On Behalf Of Brandon<BR>
Nichols<BR>
Sent: Friday, November 07, 2008 2:47 PM<BR>
To: Michael Tillou<BR>
Cc: bldg-sim@lists.onebuilding.org<BR>
Subject: Re: [Bldg-sim] Exhaust, outside air and infiltration<BR>
for LEED<BR>
<BR>
My two cents...<BR>
<BR>
The same OSA for baseline vs as-designed makes sense for<BR>
occupant-required OSA, such that there is no reward for compromising<BR>
occupant health to gain LEED points.<BR>
<BR>
However, that fraction of the fumehood OSA over and above<BR>
occupancy-required is process OSA, an opportunity where LEED should be<BR>
encouraging savings. Now I'm not saying they do, just that they<BR>
should...<BR>
<BR>
And after rereading the requirements it shakes out that LEED<BR>
really doesn't give credit for reducing process outside air loads, keep<BR>
the parametric run in your model -- the local utility may see things<BR>
differently, and 'recognize you' with a big fat rebate check.<BR>
<BR>
Cheers<BR>
<BR>
Brandon Nichols<BR>
BW Nichols PE<BR>
Seattle WA<BR>
206-228-8707<BR>
<BR>
On Fri, Nov 7, 2008 at 11:53 AM, Michael Tillou <<BR>
michael.tillou@gmail.com> wrote:<BR>
<BR>
You are correct that Appendix G requires outside air to be the<BR>
same for both as-designed and baseline models. You would not be able to<BR>
claim savings for reduced ventilation airflow from a more efficient fume<BR>
hood. Similarly you cannot claim credit for reduced ventilation<BR>
airflow on displacement ventilation and UFAD systems.<BR>
<BR>
<BR>
<BR>
However I see no reason why you wouldn't be able to claim the<BR>
fan energy savings associated with a more efficient fume hood.<BR>
<BR>
<BR>
<BR>
Mike<BR>
<BR>
<BR>
<BR>
Michael Tillou, PE, LEED<BR>
<BR>
Tillou Engineering, LLC<BR>
<BR>
Williamstown, MA 01267<BR>
<BR>
P: 413-458-9870 C: 413-652-1087<BR>
<BR>
________________________________<BR>
<BR>
From: bldg-sim-bounces@lists.onebuilding.org [mailto:<BR>
bldg-sim-bounces@lists.onebuilding.org] On Behalf Of Bishop, Bill<BR>
Sent: Friday, November 07, 2008 9:04 AM<BR>
To: bldg-sim@lists.onebuilding.org<BR>
Subject: [Bldg-sim] Exhaust, outside air and infiltration for<BR>
LEED<BR>
<BR>
The mechanical engineer for a campus laboratory building with<BR>
100% OA wants to claim energy savings for reduced exhaust from more<BR>
efficient fume hoods. (Established design practice uses hoods with 100<BR>
fpm flow - they are installing 70 fpm hoods. This reduces peak exhaust<BR>
from 700 to 490 CFM per hood.) My approach has always been to keep<BR>
outside air, exhaust and infiltration flows identical between the<BR>
proposed and baseline models (except for DCV). (This was not easy for<BR>
this model with proposed VAV and baseline constant volume packaged<BR>
rooftops.)<BR>
<BR>
<BR>
<BR>
Has anybody successfully claimed OA/exhaust/infiltration savings<BR>
for a LEED project?<BR>
<BR>
<BR>
<BR>
Thanks,<BR>
<BR>
Bill<BR>
<BR>
<BR>
<BR>
William Bishop, EIT, LEED(r) AP | Pathfinder Engineers LLP<BR>
<BR>
Mechanical Engineer<BR>
<BR>
<BR>
<BR>
3300 Monroe Ave., Suite 306<BR>
Rochester, NY 14618<BR>
<BR>
TEL (585) 218-0730 Ext. 114<BR>
FAX (585) 218-0737<BR>
<BR>
bbishop@pathfinderengineers.com<BR>
<BR>
<BR>
<BR>
www.pathfinderengineers.com<BR>
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