[Bldg-sim] LEED and existing envelopes
Nick Caton
ncaton at smithboucher.com
Tue Oct 11 15:17:35 PDT 2011
James, your logic and resulting conclusions appear spot on to me, for
what it's worth =).
NC buildings do seem to have an easier time being designed as a fishbowl
than existing buildings turning into one (speaking qualitatively here).
I could only speculate as to whether that's by design or accident on
USGBC's part. My guess is it's an unintentional result of NC baselines
being necessarily more arbitrary-to-reality. Perhaps this
"difficulty-gap" between NC and EB modeling is something the EA tag
committee could or has already addressed?
I think you can take your conclusions a step further and say that the
present LEED system holistically, through the energy modeling credits
and their relative importance in v3 onwards, is very much discouraging
allocating your project budget towards converting existing buildings
envelopes to glass walls, and conversely encouraging spending your
dollars elsewhere to net a "more green" energy result... In the "spec
office scenario" below with daylighting credits out of the picture, it
would appear LEED is giving a clear NO signal to any window/shading
upgrade that doesn't provide a net energy benefit on its own.
Speaking outside of the confines of LEED, I won't say this is
necessarily reasonable... I personally would work more productively in a
relatively inefficient office with a great view than a more efficient
cave - which would result in more quality building systems getting
designed for the world to enjoy ;). LEED by its nature has an
inescapable "social policy" side where value judgements are being made
in spite of what building design professionals and owners know/ think.
Constructively, perhaps the rules could be improved from "never install
glazing" to encourage "install glazing and do a quality job of
minimizing the negative energy impact." That's what we'd do without
such constraints. Then again, perhaps the powers-that-be cannot accept
that daylighting/views have an impact that is not measureable in a
utility bill... or perhaps those powers need to spend some extended time
in a cubicle farm? :-)
Again, haven't done a LEED-EB model myself, so I'm only speaking from my
"outside the LEED box" renovation modeling experience.
I also emphatically agree daylighting controls are not a panacea to
energies burned/lost with windows (and even if they were, they're too
expensive to be treated that way responsibly), but should be budgeted
and considered as part of a cohesive & deliberate window/shading/space
layout strategy. The concept of "ideal WWR" becomes a very dynamic,
complex and climate/project-specific problem when daylighting controls
are involved... All the more reason to engage (and compensate) your
energy modelers early in design, though I know I'm preaching to the
choir!
~Nick
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: James Hansen [mailto:JHANSEN at ghtltd.com]
Sent: Tuesday, October 11, 2011 2:10 PM
To: Nick Caton; Paul Riemer; Anne Juran; bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] LEED and existing envelopes
Well wait a second - if I have a building with no windows, and I go to
one with say 40% glass, there is going to be a huge increase in energy
consumption, and we can't assume it will be offset by daylight
harvesting as that is an expensive thing for a spec office building
developer (as an example) to provide. And this particular building is
not getting any of the daylight and views credits because of shape. (so
Paul, it is truly a net penalty to add windows, especially since we're
talking about at least 2 or 3 EAc1 pts).
There is only a 4% savings delta in the point thresholds for new
buildings vs existing buildings (3 pts under CS is 8% for existing
buildings and 12% for new buildings).
I can almost guarantee that if I am comparing a baseline existing
building with no glass to a proposed building with 40% glass, it will
show substantially worse savings than if I was comparing a baseline new
building with 40% glass to a proposed building with 40% glass. And by
substantially, I mean more than 4% worse.
With that in mind, I would actually BENEFIT from treating the baseline
building as a new building. That doesn't seem right ??
But I appreciate everyone's input. I guess I've just "snuck" 3 or 4
existing building projects thru the system.
-James
From: Nick Caton [mailto:ncaton at smithboucher.com]
Sent: Tuesday, October 11, 2011 2:54 PM
To: Paul Riemer; James Hansen; Anne Juran;
bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] LEED and existing envelopes
I've never done a core & shell model, so take this opinion with a grain
of salt (it's only my opinion):
This reviewer's interpretation seems to make a lot of sense to me. Have
the baseline represent the actual existing building, and have the
proposed match the actual design. To my understanding, the only reason
we make them match 1:1 for new construction is there isn't a better
means (like when you have an existing building) to define a baseline
that would treat evenhandedly all building types/climates/circumstances,
so we have them match to at least ensure level playing field.
Put another way, and in response to James' query, I think if adding
windows (nice or not) cause the energy bills to go up in an existing
building, then that should be reflected in the energy model.
Simultaneously, if you are interested to add daylighting "in
moderation," and locate/orient glazing & shading devices in a fashion
that lowers the annual bills, then that should also be reflected in the
energy model.
It's important to remember not all exterior glazing is bad from an
energy perspective, particularly when daylighting controls for the
building interior lighting are added into the mix. WWR is one area
where "engineers and architects" (or "energy and aesthetics," if that
better describes your design team) do not need to be on opposite ends of
the table!
~Nick
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: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul Riemer
Sent: Tuesday, October 11, 2011 1:46 PM
To: 'James Hansen'; Anne Juran; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] LEED and existing envelopes
I also agree with the reviewer. The existing envelope condition
stipulation is a double edged sword. Do you truly think it is a net
penalty on your LEED application to add windows? Other LEED points
reward daylight and views, and the thermal energy impacts of the windows
are hopefully offset by electric lighting savings.
Paul Riemer, PE, LEED AP BD+C
DUNHAM
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James
Hansen
Sent: Tuesday, October 11, 2011 1:31 PM
To: Anne Juran; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] LEED and existing envelopes
Thanks for the responses Anne and Bill. But this seems ridiculous, and
goes against everything I've done to date.
So if we have an existing building with no windows, and we want to reuse
the building structure/skin (which LEED strongly encourages), we get
penalized for wanting some daylight in the building?
I think all of the references to the "baseline building envelope shall
represent existing conditions" is intended to demonstrate that you can
use existing window and wall coefficients, NOT that you can't add
windows. But what do I know...
Does anyone know for sure?
GHT Limited
James Hansen, P.E., LEED AP
Senior Associate
1010 N. Glebe Road, Suite 200
Arlington, VA 22201-4749
703-243-1200 (office)
703-338-5754 (cell)
703-276-1376 (fax)
www.ghtltd.com <http://www.ghtltd.com/>
From: Anne Juran [mailto:juran at summerconsultants.com]
Sent: Tuesday, October 11, 2011 2:02 PM
To: James Hansen; bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] LEED and existing envelopes
I find existing envelopes always tricky because the information is not
delivered in the clearest manner. However, I think in this case the
reviewer is correct, based on 90.1 Table G3.1.5 item f under "Baseline
Building Performance" and page G-17 of the User's Manual. Also, in item
c they explicitly state that it applies to new buildings and additions,
but do not list existing (other than the little blip about alterations
and 5.1.3.)
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James
Hansen
Sent: Tuesday, October 11, 2011 10:23 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] LEED and existing envelopes
I know this has been covered before, but I just received the following
comment from a GBCI reviewer for a v3 Core and Shell project I'm working
on. The project is basically an existing 5-story warehouse with almost
no windows. Part of the renovation is adding windows. The comment is
as follows:
Table 1.4.1B indicates that the window-to-gross-wall ratio is identical
in both cases; however it is unclear whether any fenestration was added
or removed as part of the renovation. The baseline ratio must reflect
the ratio as it existed prior to the renovation and the proposed ratio
must reflect the ratio as it exists after the renovation. Revise the
Baseline and/or Proposed cases as necessary so that the
window-to-gross-wall ratio is accurately modeled and provide a revised
prerequisite form and updated energy model output summaries as
necessary.
I didn't think that this was the case - I thought that if you had an
existing building, any EXISTING-TO-REMAIN windows would show up as the
existing window type, but any NEW windows in the proposed alteration
would be matched in the baseline model and comply with the Table 5.5
requirements. Meaning the WWR remained the 1:1 as long as it was < 40%
glass.
I think this is just a matter of educating the reviewer on our building,
but I wanted to make sure that there hadn't been a shift in how GBCI
reviews existing buildings.
Thanks!
GHT Limited
James Hansen, P.E., LEED AP
Senior Associate
1010 N. Glebe Road, Suite 200
Arlington, VA 22201-4749
703-243-1200 (office)
703-338-5754 (cell)
703-276-1376 (fax)
www.ghtltd.com <http://www.ghtltd.com/>
________________________________
The information contained in this communication is confidential, may be
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________________________________
The information contained in this communication is confidential, may be
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unlawful. If you have received this communication in error, please
notify me immediately by return e-mail or by e-mail to ght at ghtltd.com
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thereof, including all attachments. Thank you.
________________________________
The information contained in this communication is confidential, may be
privileged, and is intended only for the use of the addressee. It is
the property of GHT Limited. Unauthorized use, disclosure or copying of
this communication or any part thereof is strictly prohibited and may be
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