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This is an important discussion, at least it is timely for my needs both
as a reviewer and submitter. I am very interested in hearing from
other LEED (and other energy program, HPNC, Manitoby Hydro, etc.), energy
simulation reviewers. <br><br>
And with all due respect, Gord, I do welcome your consideration and
thoughts on this issue, it needs to be made clear by the CaGBC and USGBC
as to what the intentions are as to the budget case outdoor air
requirements and exactly who "the authority having
juristiction" is?<br><br>
The first question is about "the authority having jurisdiction"
- as far as labs, health care facilities, etc. The second question
is about air system design and what constitutes proper design as far as
the outdoor air calculation and the intended long term purposes of the
facility.<br><br>
So first, "the authority having jurisdiction": <br><br>
This is an excellent question about ASHRAE 90.1; without and with Appedix
G cases; LEED - USGBC and that Review Organization and "the
authority having juristiction". For example, from the Green
Care For Health Guide, Version 2.2, Appendix G, Design Assumptions &
Procedures for Modeling for the GGHC Energy Credits:<br><br>
"Ventilation, air changes and air pressure relationships: Use
specific ventilation rates, air changes, and pressure relationships, as
required by authorities having jurisdiction. If the authorities having
jurisdiction have no specific requirements, use the requirements from
2006 AIA Guidelines for Design and Construction of Hospital and Health
Care Facilities, or most recent version. "<br><br>
Then forther on, in the same document, it states:<br>
"Process Ventilation loads: Special ventilation requirements
in a health care facility are not unusual. While Table OCC-1
quantifies the typical ventilation in a health care facility, some spaces
may require higher ventilation rates. The higher ventilation rates
shall be simulated in both the Baseline and Proposed building simulation
runs, making this an energy neutral feature. "<br><br>
From the health care prospective, ventilation is very specific and the
"authority having jurisdiction" is basically the facility and
their designers. Therefore the calculation of outdoor air
requirements would have to be accompanied by letters from that authority
- whom ever it might be. In my experience these letters typically
are submitted with a fairly detailed air system balance calculation
noting the standards the designer is following.<br><br>
I agree with this intent and I believe that the requirements for heat
recovery cover cases like this where, in reality, HVAC systems often have
in excess of 70% outdoor air and greater than 5000 cfm and therefore the
budget case system has heat recovery as a requirement (at least in
reading 90.1-2004). For smaller systems, the budget case will
perform significantly poorer than the proposed design that has heat
recovery. <br><br>
I believe that the outdoor air requirements should be based on the
minimums suggested in ASHRAE 62 and other standards such as CSA-Z317, but
each facility had to determine their outdoor air requirements and should
not be penalized by artificially restricting the budget case how the
reviewer interprets the requirements of 90.1, LEED, 62.1, CSA Z317, the
ASHRAE Application Table, Table 7.6.3 Ventilation Requirements for Areas
Affecting Patient Care In Hosptitals and Outpatient Facilities,
etc.<br><br>
For example, in the case of a University facility with a new medical
medical education facility complete with medical labs, exam areas,
etc. The "Owner" deemed certain spaces, systems as
medical facilities and mandated typical health care, higher, ventilation
rates. While not all the building falls into this category, a
reviewer must accept the design outdoor air requirements as
meeting the requirements of "the authority having jurisdiction"
and allow the budget case to have the same outdoor air amounts.<br><br>
I believe that labs any medical labs fall into this category. A
level 3 lab had very strict ventilation requirements and the budget
case will necessarily have the same outdoor air requirements and will
have any heat recovery, ventilation control as required by ASHRAE 90.1,
and the other standards to which the facility is designed.
<br><br>
SECOND - what constitutes "correct design" in terms of the
level of outdoor air delivered.<br><br>
Example, two examples, one a large long term, expandable, flexible HVAC
system on a university campus - as the building will have, at one time or
another in the detailed life cycle analysis for the facility, labs, dense
occupant lecture theatres, offices, perhaps dormitories. At any
rate, the designers have decided, in their wisdom and I mean that with
due respect, that the system should simply be a 100% OA system with
variable flow control for all current and intended space functions.
So, yes there will be offices with 100% OA. As this is a single fan
system, any critical outdoor air calculation will result in a 100% OA
system. It will have variable flow control, demand ventilation
control in zones with variable occupancy - either CO2 or occupancy
sensor. It will have heat recovery. <br><br>
In this case, the budget case will indeed be a 100% OA system, with heat
recovery as per 90.1-2004 6.5.6 and exhaust air control as per 6.5.7 (as
appropriate). I don't believe that the USGBC, its review arm, the
CaGBC, etc. can mandate that the outdoor air has to be lower because the
system has use a critical zone calculation that results in more than 20%
above the sum of the space by space, uncorrected ventilation rates - or
some other arbitrary percentage. <br><br>
In the other case, the facility is a smaller, fixed use but mixed use
facility with a small portion requiring a 100% OA system and the other
small portion being office, storage, corridors, etc. The pressure
and filtration requirements, and other design requirements (regardless of
what standards), initial cost, controllability and the other myriad of
design goals, results in a 100% OA system. It is less than 5000
cfm, and but more than 70% OA. In this case I believe that the
budget case will should have the same 100% OA system and the not have
heat recovery, exhaust control as per 90.1-2004.<br><br>
I am very interested in hearing from other LEED (and other energy
programs, 90.1, GGHC, HPNC, Manitoby Hydro, etc.) energy simulation
reviewers.<br><br>
Note that I am quoting 90.1-2004, that is the latest I can access, the
2007 electronic version has the wonderful feature of rendering itself
useless when you upgrade your computer, apparently I have to contact
ASHRAE somehow to provide an unlocking key, now where did I jot down that
password?<br><br>
<br><br>
At 04:20 PM 26/08/2010, Paul Erickson wrote:<br>
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Vikram,<br>
<br>
Good question…a bit interesting to try and answer. <br>
<br>
First, your calculations are correct. <br>
<br>
Second, it is interesting that only “educational science laboratories”
are mentioned, somehow suggesting that their use is different from
corporate and institutional labs. <br>
<br>
Third, EH&S often makes this determination and there is no agreement
among standards/guidelines dealing with lab ventilation so to impose this
bit of Std 62 seems like something that the USGBC should be considering
as it moves towards connecting Appendix G to Std 62 rates. <br>
<br>
Fourth, related to that last point, while Appendix G does not yet
directly require Std 62 rates for the baseline, LEED requires Std 62
rates for the proposed and 90.1 requires the baseline ventilation to
match the proposed. So, it would seem that models should be
reflecting the 1 cfm/sf requirement. <br>
<br>
There is a grey area that I think may also be a point of
discussion. Minimum exhaust rates of various types are often only
required when the space is occupied. As such, and considering that
many university EH&S folks are at least beginning to bat around the
notion of, if not adopt, a 4 ACH minimum during unoccupied periods, it
seems fair to have a value lower than 1 cfm/sf during unoccupied
periods. What’s your perspective on this?<br>
<br>
It’d be good if others chime in and help develop a consensus.<br>
<br>
Paul<br>
<br>
<br>
<b>Paul Erickson </b>LEED® AP <br>
SR. Sustainable Design COnsultant<br>
<br>
<b>AEI</b> | AFFILIATED ENGINEERS, INC. <br>
5802 Research Park Blvd. | Madison, WI 53719<br><br>
P: 608.236.1112 | F: 608.238.2614 <br>
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<br>
<br>
<b>From:</b> bldg-sim-bounces@lists.onebuilding.org
[<a href="mailto:bldg-sim-bounces@lists.onebuilding.org" eudora="autourl">
mailto:bldg-sim-bounces@lists.onebuilding.org</a>] <b>On Behalf Of
</b>Sami, Vikram<br>
<b>Sent:</b> Tuesday, August 24, 2010 10:49 AM<br>
<b>To:</b> bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> [Bldg-sim] ASHRAE 62 question<br>
<br>
Just going through table 6.4 in ASHRAE 62.1-2007 it looks like the
minimum exhaust rates for labs (educational science laboratories) is 1
cfm/ft2. That amounts to an ACH of 6 (for a 10ft ceiling) and 6.7 for a
9ft ceiling. <br>
<br>
Am I interpreting that correctly? Does that mean for LEED projects we
cannot go below 6 – 7 ACH? Is there a way around it?<br>
<br>
<br>
<b>Vikram Sami</b>, LEED AP<br>
Sustainable Design Analyst<br>
1382 Peachtree St. NE, Atlanta, GA 30309<br>
t: 404-443-7462 f:
404.892.5823 e:
<a href="mailto:vikram.sami@perkinswill.com">
vikram.sami@perkinswill.com</a>
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www.perkinswill.com</a><br>
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