[Bldg-sim] LEED and existing envelopes

Wed Oct 12 17:20:16 PDT 2011

Actually, existing building envelopes are generally pretty poor
performers.  Upgrading insulation levels usually  makes up for any small
penalties associated with adding a few windows, especially if high
performance glazing is used in any windows that are replaced.  I've found
it's much easier to get EA Credit 1 point in existing buildings than in
new construction.  One other simple way to get benefit in existing
buildings is by reducing infiltration rates by tightening up the envelope.
We generally try to do before and after blower door tests in existing
buildings and do an ECM to take credit for decreased infiltration.  

Morgan Heater, P.E.

BEMP, LEED AP

morgan at ecotope.com

206-322-3753 ext 209

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Tuesday, October 11, 2011 3:18 PM
To: James Hansen; Paul Riemer; Anne Juran; bldg-sim at lists.onebuilding.org
Cc: Gail Hampsmire
Subject: Re: [Bldg-sim] LEED and existing envelopes

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

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: 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

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: 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/> 

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