[Equest-users] Building area method ASHRAE 90.1

Wed May 23 14:09:46 PDT 2012

Patrick, 

I agree with Bill that it is irrelevant for energy modeler whether
space-by-space or building area method was used to document compliance of
the lighting design with the energy code (see his discussion on mandatory
versus prescriptive requirements of 90.1). As a side note, when compliance
with energy code is documented using prescriptive path (for example via
ComCheck), exceeding LPD allowances for individual space types does not mean
that project fails to comply using space-by-space method, as you seem to
imply below. Space by space method does allow trade-offs between spaces,
because it compares the total specified lighting wattage for the entire
building to the sum of space-by-space allowances (see section 9.6.1 d). I
also agree with Bill that space-by-space method is the only way to provide
meaningful feedback to the design team. It also helps to catch issues with
LPD calculations, such as treating partial or temporary lighting in core and
shell spaces as complete lighting system, or failing to include unspecified
plug-in lighting in hotels into LPD calculations. Space-by-space method also
comes with a carrot of increased lighting allowances as described in 9.6.2.

Maria 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Patrick J.
O'Leary, Jr.
Sent: Wednesday, May 23, 2012 3:41 PM
To: Bishop, Bill
Cc: eQuest Users; Oscar B.
Subject: Re: [Equest-users] Building area method ASHRAE 90.1

referencing this comment:  "The only obvious case for using the Building
Area Method to determine modeled LPD is the case that Nick mentioned where
lighting neither exists nor is specified."

or when the lighting designer/electrical engineer has higher lighting
densities that exceed one (or more) of the space-by-space maximum allowable
lpds but compensates for it by having lower lpds in other spaces such that
the whole building lpd does not exceed the maximum allowable by the whole
building method.

On 5/23/12 7:45 AM, Bishop, Bill wrote: 

Building Area and Space-by-Space are not methods for designing lighting
systems. They are prescriptive requirements for demonstrating lighting
energy compliance in 90.1. The LPD allowances in Tables 9.5.1 and 9.6.1 do
not need to be complied with if using energy modeling to demonstrate
compliance for 90.1 and for LEED. (Only the Mandatory Provisions of 9.4 need
to be met for the lighting design.) Energy modelers only need to know the
lighting power and space use categorizations of the design as shown on the
drawings (along with schedules and controls), not the process used to design
it (which typically considers light levels in footcandles or lux).

I think that if a lighting system has been designed, a strong argument can
be made that the space-by-space method needs to be used in both the proposed
and baseline cases, and that lighting power needs to be entered individually
for each space/zone.

                "If construction documents are complete, the proposed
building lighting system power is modeled as shown on the design documents."
(ASHRAE 90.1 User's Manual, p. G-17)  

"The LPD for the proposed design is taken from the design documents for the
building. The LPD specified in the models must correspond to the spaces
within each thermal block." (ASHRAE 90.1 User's Manual, p. 11-14 and also p.
G-18)

The only obvious case for using the Building Area Method to determine
modeled LPD is the case that Nick mentioned where lighting neither exists
nor is specified.

As Maria Karpman, Nick and Patrick have mentioned, you are likely to show
higher energy savings using the Space-by-Space method. Beyond that, using
Space-by-Space allows you to give valuable feedback to the design team,
which I would argue is a responsibility of energy modelers. It is routine
for me to point out areas of potential improvement of the lighting design in
every project I model, based on the allowances in Table 9.6.1. "Yes, Ms.
Architect, that is a lovely looking light fixture, but 2.6 W/ft2 of lounge
lighting is more than twice the baseline allowance." I don't know how you
give helpful feedback if you are just comparing two building-averaged
lighting power densities.

Regards,

Bill

 <mailto:wbishop at pathfinder-ea.com> 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Patrick J.
O'Leary, Jr.
Sent: Tuesday, May 22, 2012 7:28 PM
To: Nick Caton
Cc: eQuest Users; Oscar B.
Subject: Re: [Equest-users] Building area method ASHRAE 90.1

actually nick, i agree with you.  since i don't design lighting systems i
always ask the lighting designer which method they're using before i start
building a model.  almost all of the lighting designer's i've worked with
use the whole building area method, though as you point out the
space-by-space method can actually do a bit better for energy savings.

my point is that there isn't a mandate to use either the space-by-space or
whole building area method and there is no justification as far as 90.1-200x
is concerned for a usgbc reviewer to claim that the space-by-space method be
used.  the requirement per 90.1 is that the method be consistent in both the
proposed and baseline models.  space-by-space in both or whole building in
both.  this is what i've had to point out to reviewer's when i've received
comments.  just quote chapter & verse to show that the method
(space-by-space or whole building) used meets the 90.1 app g requirement and
is applied the same in both models.

as far as comcheck, comcheck reports from lighting designers are only as
good as the individual filling them out.  i've had lighting designers (with
all of their extra letters including pe after their names) fill them out
incorrectly.  i.e. not having all the lighting fixtures the same in drawing
schedules as input into comcheck, not having same number of fixtures in
drawings and in comcheck, not having the same floor areas in drawings and in
comcheck, and worst of all, not using the same methodology in comcheck that
they've used to design the lighting system in the first place.   yes, i've
seen comcheck reports that indicate space-by-space when the lighting
designer has told me whole building method.  and vice versa.  so i always
end up confirming my lighting take-offs (from the lighting plans) and
methodology with the lighting designer/electrical engineer and their
comcheck report.

On 5/22/12 3:58 PM, Nick Caton wrote: 

Hmm, I think I'm on the fence here.  

My practice is identical to Vikram's description for both energy modeling
and when documenting compliance for my lighting designs:  Choose whatever
method you wish, but always use the same approach for baseline and proposed.
This is pretty clear outside of Appendix G, when documenting compliance.
For modeling, I don't use either approach predominantly - it depends on the
project.

Since Patrick is pushing one side, I'll play devil's advocate =):  I can
affirm I've used "whole building" averaged LPD in proposed models for
successful LEED submission without incident multiple times, documenting that
clearly along the way, but I was using "whole building" for the baseline as
well in each instance.  I do not personally read 90.1 or LEED to explicitly
require LPD be defined with space-by-space for a proposed model.  Patrick, I
just checked each of your citations and the only specific call for either
method is when the lighting system has not been designed, in which case the
whole building approach is prescribed.  Keep in mind both methods should sum
to the same total installed watts for the proposed design.

Back to the neutral perspective:  I'll emphasis I do use both approaches.

To Oscar's case:  My general experience has been the whole building method
is less generous in net allowable watts when you run the numbers both ways.
In other words, you may stand to earn more LEED points by making your
baseline more detailed, using space by space.  My suggestion for Oscar is to
simply go with the reviewer's flow and possibly walk away with another point
tucked under your arm. it'll probably be a similar amount of effort on your
part relative to composing an opposing response, and you won't have to worry
about the reviewer disagreeing =).  

I agree space-by-space is 'better' for that reason alone - if different at
all, it tends to yield a better performance rating.  I will acknowledge
space-by-space is also "more accurate," notably so if you're simultaneously
defining distinct & accurate lighting schedules space-by-space, but whether
the corresponding additional time investment and resulting "accuracy boost"
are advantageous for a given LEED model is a toss-up.  I personally feel the
role accuracy plays in a LEED model is often overblown to a point of
silliness, but that's a personal call we each need to make and a whole
'nother discussion.

Hot related tip:  energy modelers and MEP designers alike need to be aware
of COMcheck.  I find it an invaluable time saver for speeding up takeoffs
for whole bldg & space by space calcs, and it's only as costly as eQuest.

~Nick

cid:489575314 at 22072009-0ABB

NICK CATON, P.E.

SENIOR ENGINEER

Smith & Boucher Engineers

25501 west valley parkway, suite 200

olathe, ks 66061

direct 913.344.0036

fax 913.345.0617

www.smithboucher.com 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Patrick J.
O'Leary, Jr.
Sent: Tuesday, May 22, 2012 4:49 PM
To: Sami, Vikram
Cc: eQuest Users; Oscar B.
Subject: Re: [Equest-users] Building area method ASHRAE 90.1

as long as a lighting system has been designed:

according to ashrae/appendix g the uniform/whole building method applies a
uniform lpd to the BASELINE building only while the PROPOSED uses what is
designed - so long as the design is based on the whole building area method.
the lpd of the PROPOSED design should not be applied uniformly to the
PROPOSED building simulation.  

see appendix g, table g3.1, section 6 lighting, subsection b, page 173
(2004), page 179 (2007).  user's manual pages g-17/18 (2004 & 2007)

i would suggest to quote table g3.1 when replying to the reviewer's comment.
i have had reviewer's tell me i have to use the space-by-space method in a
simulation for both proposed and baseline buildings.  this is not correct.
what is correct is that the simulation reflect the methodology used by the
lighting designer.  if the lighting design is based on the whole building
method then the whole building method maximum lpd is used in the BASELINE
building.  if the design is based on the space-by-space method then the
space-by-space maximum lpd for each space type is used in the BASELINE
building.  in either case the PROPOSED building should reflect what is
designed.  by 'what is designed' i mean look at the lighting plans, lighting
schedules, and enter the lpd for each space/zone (thermal block) based on
the number of fixtures, watts per fixture, and square feet of space.

On 5/22/12 2:15 PM, Sami, Vikram wrote: 

The building area method applies a uniform LPD to the entire building. If
you do that in your baseline, you need to apply a uniform LPD to you
proposed building too. 

In general, I don't recommend using the building are method - the space by
space method is a better approach. 

Vikram Sami, LEED AP BD+C

Sustainable Design Analyst

1315 Peachtree St. NE, Atlanta, GA 30309

t: 404-443-7462    f: 404.892.5823       e: vikram.sami at perkinswill.com
<http://www.perkinswill.com/> www.perkinswill.com

Perkins+Will.  Ideas + buildings that honor the broader goals of society

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Oscar B.
Sent: Tuesday, May 22, 2012 4:38 PM
To: eQuest Users
Subject: [Equest-users] Building area method ASHRAE 90.1

How does the building area method work?

I just got a comment from the review team for a project pursuing LEED
certification.

I used the building area method for the baseline case and in the proposed
case I put the LPD from the lighting design. However they told me that the
same method has to be used in both cases.

Any help would be appreciate.

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