[Bldg-rate] [Bldg-sim] Fwd: LEED+90.1 Process/Plug Loads Conundrum
Nick Caton
ncaton at smithboucher.com
Fri Apr 30 16:31:03 PDT 2010
Firstly, apologies for the cross-posting, but it appears this topic has
grown include many lists so I can't come up with an alternative!
Secondly, a huge thanks to Carol, James and a large number of others
(who shall remain unnamed until they should decide to join the public
discussion) who have given me direct input on their personal thoughts,
outside of the mailing lists.
I have received a flood of suggestions regarding approaches when the
intent is to follow the 25% rule, and additionally regarding how one
might go about appeasing a USGBC LEED model reviewer when attempting to
document a lower figure. My impression up until this point, based on
colleagues' experience/advice, has been that attempting to substantiate
anything less than 25% process loads would be a futile task and would be
flatly rejected. As a result I never really considered this to be an
option available to us LEED energy modelers. I now understand that for
many, documenting something less than 25% has proven a feasible, if
occasionally exhaustive, task.
When the intent is to follow the 25% baseline process load prescriptive
requirement, I have been exposed (again outside of the lists) to a
surprising number of unique viewpoints and seemingly legitimate
approaches which have led to successfully reviewed LEED model
submissions for others.
Among the approaches to build the process loads to 25% are:
- Adding a single direct internal/external load to the project
electrical meter in addition to the designed space equipment loads -
this approach avoids additional internal heat gains.
- Adding additional or redefining designed space equipment
loads, adding internal heat sources. If and when these additional loads
should result in too many unmet cooling hours in the proposed model,
there are two basic approaches:
o Specify larger system cooling capacities and/or airflows
o Allow those systems cooling capacities/airflows to auto-size
- Keeping the designed space equipment loads without adding any
further, but modifying their utilization schedules to increase space
equipment usage during non-peak cooling hours - this of course adds heat
to the models, but avoids unmet cooling hours due to clashes with
proposed system cooling capacities.
I sincerely hope Carol and others will not misunderstand... Myself and
others do not wish to "game the system," but we seem to have a variety
of viewpoints as to what the intent is for the 25% rule.
If it may help and add to the discussion, my personal opinion leading up
to this inquiry has been that the default 25% rule exists simultaneously
as a means of normalizing the "difficulty level" of attaining LEED EAc1
points for projects with various actual process loads. Perhaps at some
point in time, somebody decided it would be unfair for someone designing
a LEED Platinum toolshed with zero process loads to have an easier time
of it than some poor sucker trying to get some EAc1 credits for an
automotive manufacturing facility with immense process loads?
I will unfortunately be unable to participate in or respond to this
topic of discussion for some time as I will be away from my inbox. I
very much look forward to gaining a better understanding of how we as a
group might come to agree on a "best practice" for this issue. If
anyone should currently have access to a relevant CIR that would
probably be very useful.
A humble thanks again to everyone,
~Nick
NICK CATON, E.I.T.
PROJECT ENGINEER
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
fax 913 345.0617
Check out our new web-site @ www.smithboucher.com
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Carol
Gardner
Sent: Friday, April 30, 2010 5:12 PM
To: bldg-sim at lists.onebuilding.org; eQUEST Users List
Subject: [Bldg-sim] Fwd: [Bldg-rate] LEED+90.1 Process/Plug Loads
Conundrum
---------- Forwarded message ----------
From: Carol Gardner <cmg750 at gmail.com>
Date: Fri, Apr 30, 2010 at 2:40 PM
Subject: Re: [Bldg-rate] LEED+90.1 Process/Plug Loads Conundrum
To: James Hess <JHess at tmecorp.com>, Nick Caton <
ncaton at smithboucher.com>, Karen Walkerman <kwalkerman at gmail.com>
Cc: "bldg-rate at lists.onebuilding.org" <bldg-rate at lists.onebuilding.org>
Hi Nick,
I'm glad you raised this issue.
First, I agree with James, and have heard from other people, that LEED
accepts documentation saying something as basic as "hey, I don't have
25% plug loads".
Second, when you have to create a baseline to measure up from, you are
forced to say what that baseline is. For instance, in 1985-86, working
on the BPA-funded Energy Edge project, we had to figure out the baseline
for a group of buildings being designed to exceed the current energy
codes by 30%. We didn't have a baseline then. To deal with this we
assembled a group of people that we euphemistically called The
Greybeards (so sorry to you all). The tables now known as G3.1.1A &
G3.1.1B in Standard 90 came out of what we created in that moment of
time. We were trying to limit what is called "gaming the system"
So now it seems it has been deemed important to control the baseline a
little more: by specifying plug loads at 25%. The goal of trying to
limit gaming the system might be the source of the 25%. The danger which
Nick has clearly demonstrated in his email is that what is meant to
control gaming the system, may now actually be creating it.
Further thoughts/comments welcome,
Carol
On Fri, Apr 30, 2010 at 1:42 PM, James Hess <JHess at tmecorp.com> wrote:
This is a good question. On prior projects we have worked on, I
have found that you can have less than 25% plug loads, so long as you
have some documentation to back it up.
For example, we are currently working on a prison project. The
plug loads are very low for obvious reasons; they don't provide stereos,
computers, ipods, TV's, etc. to the inmates (typically, all they get is
an alarm clock/radio that uses ~ < 10 watts). There is no way on this
project that we could get the plug loads to come in at 25% unless we
artificially jacked them up to levels that would never exist in reality.
We would have a similar problem in that the Proposed Design equipment
would not be able to cool the spaces. So, we just document the loads we
do have and I believe we are good. The project has been through the 1st
review and this has not come up as an issue.
I believe we have had other projects where we documented the
loads we had and passed the review with no problems. We will typically
develop a simple spreadsheet and document the internal loads that each
room has. That is easy enough to do these days I believe, for most
applications. For example, a typical desktop computer uses about 65
watts on average, monitor = ~ 45 watts (depending on size), clock radio
~ 10 to 15 watts, etc. you get the point. (get a "Killawatt" power
meter from Amazon and have some fun taking some measurements to see
approximately how much power stuff uses, guaranteed to provide hours of
fun).
Just provide some documentation on some good reasonable
estimates for the loads and I think you will be fine.
An alternate method is to use default values from Table G-B from
the ASHRAE 90.1-2007 Users Manual.
For example, the Receptacle Power Density for the Office
Building Type is 0.75 watts/SF per Table G-5.
If using that value results in the process loads being less than
25%, my comment to the reviewers would be that the 0.75 watts/SF is the
value determined by ASHRAE to be appropriate for the building type.
I think the most important thing is to use something reasonable
and defendable, and make it the same between the Baseline and Proposed
Design energy models. Our experience indicates that it does not have to
be exactly 25%, can be less than 25% or greater than 25%, depending on
the building.
One thing that is interesting is that on federal projects, per
EPACT requirements, you do not have to factor in the process/recep loads
for the purpose of determining whether the 30% savings requirement has
been met. That makes it easier to show 30% savings.
Thanks!
Regards,
JAH
James A. Hess, PE, CEM
Senior Energy Engineer
TME, Inc.
Little Rock, AR
Mobile: 501-351-4667
From: bldg-rate-bounces at lists.onebuilding.org [mailto:
bldg-rate-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Friday, April 30, 2010 12:55 PM
To: bldg-rate at lists.onebuilding.org
Subject: [Bldg-rate] LEED+90.1 Process/Plug Loads Conundrum
Something new occurred to me this week and I'd love to hear
others' thoughts!
LEED prescribes baseline/proposed energy models to follow ASHRAE
90.1 with a caveat: the "process energy costs" must total 25% of the
baseline energy costs. By extension, 90.1 requires the same
loads/schedules be applied to the proposed model as they have to match.
As an aside, the LEED EAc1 templates appear to calculate/check this
using process energy consumption (not cost), but that's not what I'm
getting at...
I just had a typical case where I had to inflate the baseline
internal miscellaneous equipment loads to get to 25%. These additional
loads were substantial enough that when applied to the proposed
model/design, I ran into many unmet cooling hours for the equipment
capacities entered.
Then I realized: We can define additional equipment electricity
loads but simultaneously apply a multiplier (in eQuest anyway - I expect
this is feasible other programs also) to reduce/negate the corresponding
heat load contributions. This results in the energy consumption/costs
showing up correctly in the final results/reports, but does not
artificially inflate the internal loads that the baseline/proposed
systems must handle.
Would this practice (which incidentally can be a time saver) of
accounting for extra process/miscellaneous loads without extra thermal
contributions be in line with the intent of ASHRAE/USGBC? It would
still normalize the otherwise unstandardized process consumption/costs
of the baseline/proposed models between different building types...
On the other hand, if it really is the intent of USGBC to add
arbitrary additional internal heat loads to our models that our actual
designs were not designed and sized for, does it follow that we should
allow the proposed models to autosize cooling equipment/fan capacities
and not specify them (this would seem incongruous with 90.1 to me)?
~Nick
Error! Filename not specified.
NICK CATON, E.I.T.
PROJECT ENGINEER
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
fax 913 345.0617
Check out our new web-site @ www.smithboucher.com
<http://www.smithboucher.com>
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