existing buildings/alterations

20 posts / 0 new
Last post

This question isn't eQuest specific, but deals with 90.1 interpretation.

For an existing building, with regards to shell alterations, G3.1.5-f says
that "the baseline building shall reflect existing conditions prior to any
revisions that are part of the scope of work being evaluated." Is this
statement as far-reaching as I believe, indicating that U-values, SHGC etc,
listed in Tables 5.5 and Appendix A are ignored in a similar way as done in
the proposed, since the "baseline" in this case is a real design, rather
than a hypothetical baseline?

Kent Beason

kbeason's picture
Offline
Joined: 2013-02-21
Reputation: 0

Kent,

Yes, for existing buildings, use the wall & roof assemblies, glazing properties etc. of the existing building for the Baseline values. Also, you don't have to simulate in four orientations.

Regards,
Bill

William Bishop, PE, BEMP, BEAP, LEED AP

Bill Bishop's picture
Offline
Joined: 2012-02-25
Reputation: 7

Agreed. Take note there are a couple nuances between what's written in 90.1 and what's required by the LEED reviewership. I believe they draw a line in the sand where if more than 50% of a project is "retrofit" vs. NC by square footage, then rotations go away.

I just had 3 LEED projects wrap up at silver/gold where in the initial submission I used thoroughly documented prescriptive baseline envelopes and 4 rotations. The preliminary review commentary required changing the envelopes to remove the rotations and match reality instead. The previous reality was (mostly) uninsulated grout filled block walls, single pane windows without film treatments, and zero wall insulation =D!

As a net result, each of these projects jumped way up in unanticipated modeling credits. It was a good day.

Outside the constraints of LEED, the closer your baseline models can reflect existing realities, the better and more informative the results of your models become for a retrofit analysis.

Regards,

~Nick

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.

Nick-Caton's picture
Offline
Joined: 2011-09-30
Reputation: 805

Thanks for the feedback. As I asked Bill offline, and I feel it goes
without saying, but never hurts to be thorough :-): this applies to the old
HVAC systems too, correct? Obtaining the old HVAC system info could be a
daunting challenge unfortunately.

I've learned alot about nuances... One area of this building is storefront
(essentially 100%) single pane glass around the whole perimeter!

Kent Beason

kbeason's picture
Offline
Joined: 2013-02-21
Reputation: 0

Kent,

I didn't notice your message was only to me. I assumed it would be a matter of seconds before others replied in the negative. The "existing conditions" caveat applies only to the envelope. You must use the Appendix G baseline systems and plants for the LEED Baseline, with the possible exception of the central plant for DES systems as you mention.

~Bill

Bill Bishop's picture
Offline
Joined: 2012-02-25
Reputation: 7

Bill,

Okay...I would classify this as one of those nuances that Nick characterized
earlier. It seems strange to me that this would only apply to the envelope,
but after all, it is only stipulated in Table G3.1 under Section 5f Building
Envelope.

To complicate the issue though, someone else's response was to use existing
HVAC systems. Normally I would dismiss his response out of hand, but he was
a LEED reviewer at one time and is more 90.1 knowledgeable than me
currently. I was about to send this message, sure that I would model
baseline per Appendix G, until I thought to look in Section 6. Does Section
6.1.1.2 provide the adequate Exception to clarify that old HVAC systems must
be modeled in the baseline for a renovation/alteration project? The term
"alteration" in the definitions appears to be applicable as an "addition" as
shown in this Exception of 6.1.1.2. However, the verbiage "shall not be
required to comply with this standard" implies that it's optional.

Kent Beason

kbeason's picture
Offline
Joined: 2013-02-21
Reputation: 0

Kent,

The exception to 6.1.1.2 (allowing existing systems to handle the HVAC needs of additions) provides a way to comply with Standard 90.1 without replacing existing systems. But your question is not about 90.1 compliance, it is about Appendix G modeling (presumably for LEED New Construction). Table G3.1 (10.) is clear on the Baseline HVAC system requirements and provides no exception for existing buildings. There may be exceptions if this is for a utility incentive program or some other application other than for a LEED NC model. Otherwise, I am not aware of any CIRs or other interpretations that would allow modeling existing systems in the Baseline.

~Bill

Bill Bishop's picture
Offline
Joined: 2012-02-25
Reputation: 7

What about G1.3 where it states that

"only parameters related to the systems to be modified shall be allowed to vary. Parameters relating to unmodified existing conditions or to future building components shall be identical for determining both the baseline building performance and the proposed building performance."

Doesn't this apply to HVAC as well as the envelope?
?
Daniel Knapp, PhD, P Phys, LEED? AP O+M

Daniel Knapp's picture
Offline
Joined: 2011-09-30
Reputation: 0

I guess to follow up the interpretation is as such:

If the existing systems are left in place, the proposed and baseline are modelled identically according to the existing systems.

If the existing systems are *replaced*, the proposed is modelled according to the replacements, and the baseline is modelled according to the 90.1 Appendix G requirements.

Best,
Dan

?
Daniel Knapp, PhD, P Phys, LEED? AP O+M

Daniel Knapp's picture
Offline
Joined: 2011-09-30
Reputation: 0

Dan,

You bring up a section of Appendix G that I have never seen discussed on Equest-users or Bldg-Sim. The 90.1 User's Manual seems to explain G1.3 in terms of including or excluding a portion of the building from the Appendix G analysis. You could choose not to model the existing portion of a building if you are doing an addition, if certain conditions are met. It is not clear to me whether or not this allows existing systems to be modeled for the baseline if they are not replaced as part of a gut rehabilitation. Either way, we agree that you model Appendix G systems in the Baseline if there are new systems in the proposed design.

Regards,

Bill

Bill Bishop's picture
Offline
Joined: 2012-02-25
Reputation: 7

Dan/Bill/Kent,

I guess I'm fortunate to be in the ESCO business where such esoteric questions don't come up. When it comes to HVAC and central plant equipment to be replaced, we will determine a likely baseline cooling efficiency based on rated efficiency and account for age and conditions that reduce existing equipment cooling efficiency, such as dirty coils & filters, crumbling fins on air-cooled condensers, scaled condensers, short refrigerant charge, excessive approaches, or air in the condenser of chillers. Although it's possible (but expensive) to field measure performance of a chiller in the field, it's virtually impossible for DX equipment. That's where the determination of baseline cooling efficiency is as much art as science.

My best,
Mike Busman

Michael R. Busman, CEM

Busman, Michael R's picture
Joined: 2012-07-12
Reputation: 0

I?ll add that of the few times this has come up for me, the result was that since HVAC systems weren?t being modified and envelope also wasn?t modified (and in a few cases neither was lighting being changed) ? in which case the project goes into LEED CI instead of LEED NC. Then a model may not have been required.

I?m not sure of the reference, but to be included as a major renovation in LEED generally two of the three would have to be modified among envelope, lighting, and HVAC. Otherwise it makes a great match for commercial interiors depending on the ownership of the building, percent owner-occupied, etc.

But the point being, many projects that have this dilemma about existing HVAC also end up not needing a model at all, so it?s a bit of a self-selecting process that it doesn?t come up as often.

Maybe you are suggesting that there might be some cases to model existing systems as-is where they are in a separate part of the facility but providing service to the project as an addition. But anything inside the project boundary would be Appendix G baseline for lighting or HVAC. Practically speaking this would be mainly applied to tapping off of existing AHUs, since service from existing chilled water or heating systems would fall into district energy guidance if this was a LEED project.

David

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

David Eldridge's picture
Offline
Joined: 2012-05-08
Reputation: 1

I know this has been discussed before, but with an existing building, it
is "possible" to calibrate the model to the weather and setpoints and
then iterate efficiencies to get them to match.

No?

Robert Wichert P.Eng. LEED AP BD&C

RobertWichert's picture
Offline
Joined: 2011-10-02
Reputation: 201

That's one of the many dials one can turn to do it. As I said, it's as much art/black magic as science. I also like to get our lighting auditors to give me actual lighting power densities by room and annual kWh from measured, observed, or agreed to hours of lighting operation. Use of the Kill-A-Watt meter, available from Home Depot for about $25 is a good way to monitor 115V plug load equipment in order to get another somewhat measured data point to define the existing building and operation.

I prefer to get as much data on the existing building as possible as you're trying to calibrate historical consumption and demand against a weather file that is representative of long-term conditions and not the period covering the historical consumption.

Mike

Busman, Michael R's picture
Joined: 2012-07-12
Reputation: 0

Mike,

I don't know how good it is, and I consider it something of a parlor
trick really, but EnergyPro claims to calibrate the as-found data to
actual weather data using NOAA historical data from the weather station
closest to the site.

This is how their Help File puts it:

Normalize Billing Data

Check the box to download the normalized weather data file from the NOAA
Web site.

This feature is not discussed in the EnergyPro manual.

Quite a trick though, in my humble opinion.

Robert Wichert P.Eng. LEED AP BD&C

RobertWichert's picture
Offline
Joined: 2011-10-02
Reputation: 201

I sense we're choosing words carefully here...?

A calibration model, provided *sufficient* quantity and quality of input information regarding the rest of the building, can certainly be leveraged as a tool to inform what "correction/de-rating" factors ought to be applied to existing rated equipment/process efficiencies, using the actual utility bills as a guidepost.

The line where *sufficient* is drawn is of course tricky to pin down in procedure for many buildings, but my experience with calibration models has taught me there are observable patterns and trends in the annual consumption / demand curves that can inform & quantify the definite need for a "correction factor" for an isolated enduse. These same observations often make it clear when there's missing information to collect elsewhere in the model.

In my opinion, opting to seek and define such corrections appropriately demands consideration, affirmation, and observation (where possible) of the expected causes, so as not to exceed the magnitudes of effect that may be reasonably expected. Mike has provided some sound examples. Ongoing testing and field measurements, where it fits the budget, can complement and enhance the process of model calibration quite a bit.

Speaking to where science and art blur here... I personally think some of the most fascinating corners of this industry of energy modeling services lie in the "art" of calibration and SD phase modeling. In these venues, the rules and knowledge we learn and hone in controlled/accountable design and more typical prescriptive/comparative analyses come together to shape meaning, understanding, and direction out of the raw unknowns and unknowables. Evokes Will Durant: "Every science begins as philosophy and ends as art."

~Nick

NICK CATON, P.E.

Nick-Caton's picture
Offline
Joined: 2011-09-30
Reputation: 805

Robert,

Although I've dabbled a bit with EnergyPro, I don't really use it. I would be curious to know if the weather data is for the ACTUAL baseline period in question or long-term for the location.

I also find it interesting that the program does the calibration for you. Calibration is up to the modeler.

Do you have any better intel???

Mike

Busman, Michael R's picture
Joined: 2012-07-12
Reputation: 0

The feature is not very well documented, Mike, but I have been told by
Martyn Dodd, the owner of the software company that puts it together,
that it uses the NOAA data from year in question (you specify the start
date) and modifies the bill data for that year based on deviations from
the "standard" weather file for that location. I really don't know the
NOAA data sets well enough to say if that is hourly or monthly or what.
I go to his classes though, and I will do my best to dig into it in the
next class that I attend in a few weeks.

As I said, I consider it a bit of a "razzle dazzle" but it's interesting.

So to answer your question to the best of my knowledge it uses the
ACTUAL NOAA data for the year in question. Remember, you are comparing
actual bills to the predicted bills (which are based on long term data)
so correcting the actual bills to account for a hot summer or cold
winter during that "bill year" is what it does.

Robert Wichert P.Eng. LEED AP BD&C

RobertWichert's picture
Offline
Joined: 2011-10-02
Reputation: 201

Robert,

After the next class, please update the community on what you are able to find out.

I need to give more thought to normalizing historical consumption data for the year in question as most buildings have fixed/baseload and variable consumption. In addition to the influence of weather, the variable component could also be related to examples such as number of hotel rooms occupied, # of public events, sq. ft. of building space occupied, or number of widgets produced. I've used a multiple regression analysis in the past as a means to measure savings using heating and cooling degree days plus some other independent variable that impacts consumption to develop baseline coefficients. Then I used actual degree days and the actual qty. of what the other independent variable was to predict what the consumption would have been without energy efficiency measures being implemented. Comparing this to the actual metered consumption was the savings.........assuming the R^2 value was high enough.

Assuming NOAA or some other source has the weather data for the year in question readily available so eQUEST could go out and grab it to process into a .bin file that eQUEST can use, that would be a nice feature to add to the program. That way you'd be comparing actual consumption and demand data versus simulation results based on actual weather for the period. Jeff Hirsch/Marlin Addison, I hope you're listening.

My best,
Mike

Michael R. Busman, CEM

Busman, Michael R's picture
Joined: 2012-07-12
Reputation: 0

That's what EnergyPro claims to do, Mike.

I'll let you know.

Cheers!

Robert Wichert P.Eng. LEED AP BD&C

RobertWichert's picture
Offline
Joined: 2011-10-02
Reputation: 201