Cooling/Heating Capacity Ratios - LEED Report?

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Hi folks,

I have a seemingly simple LEED comment which has been causing me to chase my tail this afternoon. I feel like this should be really easy to document in a crystal-clear fashion, but I must be missing something:

The Task:
Document with clarity that the baseline system cooling and heating capacities are using the 1.15 and 1.25 (respectively) capacity sizing ratios as prescribed in 90.1 Appendix G.

Intuitively, I have a sense we should be able to simply and directly reference one or a series of the *.SIM reports to substantiate the systems are oversized by the appropriate factors. After spending some time digging through the reports and associated help documentation however, I'm empty-handed and do not think the actual ratio inputs (COOL-SIZING-RATI / HEAT-SIZING-RATI) are reported.

Further, I tried deriving the oversizing ratio between a system's annual PEAK (re: report SS-P) and calculated system capacity (report SV-A) as reported... but the math doesn't quite work out! It's the right ballpark, but I don't think I can write the difference off as a rounding error...

The Solution(?):
For now, I can just provide screen grabs illustrating the inputs in eQuest's spreadsheet view with relative ease, but if this is possible to document by assembling/referencing one or more additional reports for future models I'd prefer to adopt that in practice and avoid the same question down the road. If I have some misunderstanding or new nuance to learn about the reports that would be worthwhile as well =).

Any suggestions/experience?

Thanks in advance!

~Nick

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.

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i typically just do screen caps when setting up my baseline model. it's
quick, painless, and makes mothers very happy ... and is done early ...

yeah, one would think there would be a details of hvac systems output
report showing the direct inputs, but there's not. unless you're good
at creating custom reports & can create one that pulls input data from
the hvac section? if that's even data possible for equest to pull ...

or you could parse the info from the .sim file keying on just the =
system name, heat-sizing-rati & cool-sizing-rati variables.

"PSZ-1" = SYSTEM
TYPE = PSZ
HEAT-SOURCE = FURNACE
ZONE-HEAT-SOURCE = NONE
BASEBOARD-SOURCE = NONE
SIZING-RATIO = 1.15
HEAT-SIZING-RATI = 1.25
COOL-SIZING-RATI = 1.15
etc ........

Patrick J. O'Leary, Jr.'s picture
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I second Patrick, typically I just provide screen grabs of the baseline
model and send it off.

*Neil Bulger *| CEPE

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Same here regarding the screen shots, but I only provide if asked to specifically document something via review comments. On every submitted project, however, I always upload the eQuest .inp and .pd2 files so that the reviewers can just open the files and look at whatever they need to. That beats submitting reams of "input reports" which really isn't practical. I'm assuming the reviewers know eQuest enough such that if they want to verify the Cool Sizing Ratio or Heat Sizing Ratio, they know exactly where to go in eQuest to find the answers, in a matter of seconds. That seems like a pretty reasonable assumption to me.

Regards,

JAH

James A. Hess, PE, CEM, BEMP

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Thanks fellas!

I've done screengrabs often in the past and am comfortable that will satisfy the reviewer's concerns in this case, it just bugs me that where I'm confident the inputs are correct, the output reports aren't backing me up as expected...

I've also tried summing together space peak loads from the LS reports for a given system (shaky proposition anyway as they occur at different times), and still cannot find the calculated sizing to line up with my input ratios. I guess this boils down to something I don't understand yet about how the oversizing ratios are applied to arrive at the calculated system capacities... Further digging in the help files when I get time I suppose.

I don't anticipate having a problem with this review, but if anyone can fill in the gaps that would be much appreciated =)!

~Nick

PS: I didn't know others are uploading their entire models... In the reviewer's shoes, I wonder if that makes any combination of specific reports/information look suspect in comparison?

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.

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I don't think I have an answer to your question, but wanted to point out
two things:

1) Energy models are often the "property" of the design engineer,
modeler, owner, etc, and although I often upload PDFs of the .inp file
(because I'm lazy), GBCI should never be able to require this as
standard practice.

and

2) I thought the whole intent of those newer Section 1.4 excel sheets
for documenting inputs / outputs is to avoid comments like the one you
received. If you had marked those particular cells of the "General
HVAC" tab as follows:

All Baseline system cooling capacities auto-sized with 15% oversizing
per G3.1.2.2 (at the system or plant level, but not both)

Yes

All Baseline system heating capacities auto-sized with 25% oversizing
per G3.1.2.2 (at the system or plant level, but not both)

Yes

Shouldn't that be enough for the reviewer? Thought it was supposed to
make their job easier....

Were you using an older method of input documentation?

GHT Limited
James Hansen, P.E., LEED AP

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Nick,

I agree with the others that the LEED reporting should be kept as simple as possible. I also agree with James Hansen that submitting model files sets a bad precedent.

Regarding the autosizing of cooling capacity:
I did two runs on a sample model - one with COOL-SIZING-RATI = 1.0 and one with 1.15, to confirm that the COOLING-CAPACITY shown on SV-A at 1.15 is in fact 115% of the capacity at 1.0 when the COOLING-CAPACITY is not specified.

I believe the reason that the autosized COOLING-CAPACITY as reported on SV-A is not matching the peak cooling load from SS-A (or SS-J) is that the correction factor from the COOL-CAP-FT curve is applied during the sizing routine. The peak cooling load is not likely to coincide with the rating conditions at which the curve is normalized. For instance, the DX-COOL-Cap-fEWB&OAT curve is normalized at 67F Ewb and 95Fdb OAT. The curve accounts for the fact that DX cooling capacity increases when the OAT decreases. If the OAT at peak cooling load is less than 95F, the autosized capacity will be less than the peak load. The COOL-CAP-FT curve causes the hourly cooling capacity to be higher at lower OAT.

Regards,
Bill

William Bishop, PE, BEMP, LEED AP

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Oh, I suppose I should clarify the project in question was submitted and the EAc1 credit was marked 'complete' > 1 year ago, and is only now being reviewed, so the associated EAp2 spreadsheet issn't nearly so far along in development as what you'd encounter under a current project!

If anyone else should has to answer to the same commentary in any case, seems pretty universal to respond in kind with screenshots of the input fields.

~Nick
[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.

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FYI, I never said that uploading the eQuest .inp and .pd2 files should be required, just that it should be considered, because it's easier to upload these files to facilitate the review versus uploading 1000+ pages of inputs. It's much faster to look at the actual model than reports, so I guess I don't understand why submitting the models would be considered bad precedent. I have done that on every LEED project I have submitted, which is ~ 30 +/-.

Currently, I think there is a loophole here that could be exploited. One could easily submit a Table 1.4 spreadsheet and input reports that do not match the results in the EAp2 form, or the output reports. Submitting the actual energy modeling files closes this potential loophole because the inputs and results can be verified at the same time.

That may be going too far, and this is basically all on the honor system I realize, but I think it would be a good idea.

Regards,

JAH

James A. Hess, PE, CEM, BEMP

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I understand the whole 'nothing to hide' mentality but I have a few cautions. While GBCI has been doing most reviews in house, I expect they still reserve the right to contract for review which opens the possibility that a submitted model could be forward to a direct competitor. On my first LEED submission the reviewers took issue with some of the modeling aspects, declared a lower savings percentage and made the project appeal. If the reviewers had the model in hand they might have "fixed it" themselves to determine the savings and not entertained any appeal. Since the USGBC will have utility bills from the first few years of a project's life providing them with a model is just asking from them to use it for a third party M&V exercise on what your project really saved. These might be farfetched but why risk it, just send them the reports that they request and be done.

Regards,
Paul Riemer, PE, LEED AP BD+C

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That's a good point.

To summarize ... on the one hand, if we don't submit the models to GBCI, the GBCI leaves themselves open to the potential for chicanery on our end. On the other hand, if we submit the models to GBCI, we modelers leave ourselves open to the potential for chicanery from the GBCI/USGBC's end.

We certainly don't live in a perfect world, but, I go back to the main reason for doing this --> save time versus assembling input reports.

I don't care what the GBCI/USGBC does with the models after I submit them, but I can certainly understand the concerns for potential issues.

Thanks! :)

Regards,

JAH

James A. Hess, PE, CEM, BEMP

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