[Equest-users] DOAS in baseline

[Mirza Sajjal]

This is a CIR that was recently answered in regards to DOAS systems in
the baseline:

 

FINAL Ruling:

The applicant is requesting clarification of the baseline building
modeling requirements for outside air delivery and energy recovery when
the proposed design system utilizes a 100% dedicated outside air unit
ducted to zone fan coil units, and where each fan coil unit has a supply
volume less than 5,000 cfm and an outside air ratio less than 70%. The
baseline building should be modeled with the systems defined in ASHRAE
90.1-2007 Appendix G Section G3.1.1, with ventilation rates identical to
those of the proposed building, and with untreated outside air ducted
directly to the units (no dedicated make up air unit). Energy recovery
would not be required for the Baseline Case for this project since the
energy recovery requirement is determined based on the properties of
each individual Baseline Case air handler (not based on the total
building supply air flow and percentage outside air).  Fan coils or air
handlers in the Baseline Case would be required to be modeled with
energy recovery only if the conditions of Section G3.1.2.10 apply (i.e.
design supply air capacity for the air handler greater than 5,000 cfm
and a minimum outdoor air supply of 70% or greater).

 

Mirza

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick
Caton
Sent: Thursday, January 27, 2011 2:17 PM
To: David Eldridge; Susan F
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] DOAS in baseline

 

Susan et al:

 

"Where it's not allowed" is found simply where the quantity of systems
is mandated:  3.1.1.  Model reviewers will actively challenge baseline
system quantities & exceptions taken if they suspect this isn't being
followed to the letter.

 

You should probably inform your colleagues that System 8 is VAV and
would not be CV in any case.  You might leave it at that for your own
sanity, but this segways into a shaky possibility...

 

I mentioned 3.1.1 has exceptions - some of these would dictate the
baseline have a single-zone unit of type 3 or 4, which would be (!)
constant volume, if the zone is significantly different from the rest of
the model - read those exceptions carefully.  I have never tried this,
but you might explore applying one of these exceptions (which were
almost certainly not intended for artificial dummy zones in eQuest/DOE2
models) to force an analogous type 3 or 4 baseline system to a DOAS
dummy zone...  I would personally not advise this approach but I'm
bringing it up so you might consider all angles if you're having to
argue your case.

 

It's totally possible the proposed DOAS design will ultimately cause a
net performance decrease - if so, the most you can do is focus on
ensuring the proposed system is designed well and is being modeled
correctly.  

 

Proposed:  You should carefully explore the DOAS control sequences to be
sure you're addressing its setpoints, efficiencies and when it's VAV
fan(s) do and don't run.  Much of this is often buried in submittal
information and cryptic control sequences that only the designer may
understand.  If it's a challenge (and it usually is) I'd encourage you
make a quick "fill in the blank" for all inputs and have your colleagues
research & fill it out for you.  

 

Baseline:  Do explore fan energy bump-ups per Bill below.  

 

I'm going to tangent a bit - I hope this helps you, but this is
partially a form of selfish venting also =):

 

Remind your colleagues that the baseline is what it is: an arbitrary,
imaginary system that may not be a realistic design, but is supposed to
represent the minimum requirements of the 90.1 standard.  Nobody can
claim a design is "efficient" or suggest it's "inefficient" without a
reference, and 90.1 baseline models are (often) a poor reference in this
context, as they are supposed to be arbitrary to an extent.
Unfortunately, some entities adopting & enforcing the USGBC/LEED rating
system and the finger-pointing culture that occasionally surfaces
through the submission process have collectively done a lot to suggest
the contrary: that such baseline models fundamentally represent some
form of real-world design (rather than a set of minimum requirements in
an energy standard), and so may be appropriately used to accurately
judge the value of a building's designers.  Some designers & LEED
project managers will, in turn, "pass the buck" and judge the value of
the person doing the energy modeling when the numbers aren't favorable.

 

No (practical) energy standard could account for all the variables and
design constraints of real-world building design - there will inevitably
be disconnects where "good" real-world design decisions are not rewarded
(even punished) in a rating system using a baseline based on an energy
standard.

 

People shouldn't have lose sleep over this, but they do.  We as energy
modelers sometimes have a duty to both inform and set an example in this
industry's culture.  

 

~Nick

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: David Eldridge [mailto:dse at grummanbutkus.com] 
Sent: Thursday, January 27, 2011 10:38 AM
To: Susan F
Cc: Nick Caton
Subject: RE: [Equest-users] DOAS in baseline

 

A baseline DOAS would probably have to have heat recovery (many
exceptions of course), that may not be required in your 1 per floor
AHUs.

 

 


 

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, HBDP

Grumman/Butkus Associates

 


 

 

From: Bishop, Bill [mailto:wbishop at pathfinder-ea.com] 
Sent: Thursday, January 27, 2011 10:35 AM
To: Susan F; Nick Caton
Cc: equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] DOAS in baseline

 

Susan,

 

My short answer is no, there is nothing in Appendix G that requires you
or allows you to model a DOAS system that preconditions outside air. As
you and Nick said, first use G3.1.1 for the system type. Then refer to
G3.1.2.10 to determine if exhaust air energy recovery is required. Keep
minimum outside air requirements identical between the baseline and
proposed per G3.1.2.5. If the DOAS penalizes your proposed design from
an energy perspective, check Table 6.5.3.1.1B for potential adjustments
to your baseline fan pressure drop, per the note to Table G3.1.2.9.

 

Regards,

Bill

 

William Bishop, PE, BEMP, LEED(r) AP | Pathfinder Engineers & Architects
LLP

Mechanical Engineer

 

 134 South Fitzhugh Street                 Rochester, NY 14608
T: (585) 325-6004 Ext. 114            F: (585) 325-6005

wbishop at pathfinder-ea.com           www.pathfinder-ea.com
<http://www.pathfinder-ea.com/> 

P   Sustainability - the forest AND the trees. P    

 

 

From: Susan F [mailto:modelsenergy at gmail.com] 
Sent: Thursday, January 27, 2011 10:31 AM
To: David Eldridge
Cc: Nick Caton
Subject: Re: [Equest-users] DOAS in baseline

 

I don't necessary but I have co-workers convinced that it will help us.
They want to claim savings for using a VAV OA system by saying that the
baseline would be constant volume and also want to claim savings for
other control measures.  I don't really buy this because I can't see
where 90.1 would allow that.  But they are arguing that they can't find
where it's not allowed.  

On Thu, Jan 27, 2011 at 11:26 AM, David Eldridge <dse at grummanbutkus.com>
wrote:

I'm not sure why you want to have it in the baseline?

 

 


 

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, HBDP

Grumman/Butkus Associates

 


 

From: equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] On Behalf Of Susan F
Sent: Thursday, January 27, 2011 10:13 AM
To: Nick Caton
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] DOAS in baseline

 

Nick,

So if my baseline is system 8 and I'm using 1 system per floor as
indicated in G.3.1.1, I don't really see an exception that would allow
the DOAS.  Am I missing something that would actually allow it?

 



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