[Bldg-sim] Lies, darn lies, and statistics

Tue Mar 14 13:12:08 PDT 2023

I agree that better measurement is the key. It's surprising how completely
off the radar that is. There is an expectation of major interventions, new
facades, plant replacement, etc, but the basics get neglected.

I have a theory about using statistical models to assist with simulation
models. In theory, we should not just aim for low rmse, but coefficients
should be comparably close when performing the same regression on simulated
results.

Some more words of wisdom :)
https://en.wikipedia.org/wiki/There_are_unknown_unknowns?wprov=sfla1

On Tue, 14 Mar 2023, 19:35 David Eldridge, <DEldridge at grummanbutkus.com>
wrote:

> You are allowed to make an M&V plan and then define what you did given the
> information available. In your case you are using G14 informatively, it
> wasn’t required that you follow it or report that you were using it.
>
>
>
> The only thing I can add is maybe you can focus on validating some of the
> inputs – if the utility data is spotty then document what you do know from
> the input side – if you can show some of your most sensitive input
> variables are validated that would help give confidence  that the outputs
> are also likely to be useful.
>
>
>
> David
>
>
>
>
>
> *David S. Eldridge, Jr.**, P**.**E**.**, BEMP, BEAP, HBDP, GGF/A*
>
> Direct: (847) 316-9224 | Mobile: (773) 490-5038
>
>
>
> *Grumman|Butkus Associates* | 820 Davis Street, Suite 300 | Evanston, IL
> 60201
>
> Energy Efficiency Consultants and Sustainable Design Engineers
>
>
>
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>
> *From:* Bldg-sim <bldg-sim-bounces at lists.onebuilding.org> *On Behalf Of *Chris
> Yates via Bldg-sim
> *Sent:* Tuesday, March 14, 2023 1:10 PM
> *To:* 'David Eldridge' <dancingdavide at hotmail.com>; 'Jim Dirkes' <
> jvdirkes2 at protonmail.com>
> *Cc:* bldg-sim at onebuilding.org
> *Subject:* Re: [Bldg-sim] Lies, darn lies, and statistics
>
>
>
> I think I need to qualify this: informed by G14, but definitely not
> compliant with it! There is some allowance for repairing or “healing” data,
> but when the data has a lot of holes or modes/ category variables then
> forget it. This is my case, but the client still wants some kind of
> representative simulation.
>
>
>
> Monthly models can be garbage. School holidays cut across months at
> different times, combined heat and power is popular which complicates gas
> usage especially when metering is limited… did the heat by-product of
> electricity generation go to the building, or was it rejected? They can
> work for heating in our temperate climate, but not for cooling.
>
>
>
> Nevertheless, we need some kind of representative simulation model. We
> can’t make any ECM qualifying claims but we can do something useful. This
> is where these methods can give you a lot of insight before you start
> modelling.
>
>
>
> I hadn’t tried the IMT previously. We tend to have limited our regression
> analysis to monthly “degree day” methods (your 2p model, I think). I
> plugged some project specific daily electricity data into the MVR example
> (multi variate regression) and it seemed to give decent CVRMSE (~2-3%) but
> low R2 (~0.7). However, it appeared to provide some insight on cooling
> usage (monthly 2p models are meaningless for this in the UK’s temperate
> climate).
>
>
>
> I also made some 2p monthly models of gas. I thought these were good until
> I compared successive years. *I guess this is were understanding a range
> of statistical indices is helpful.*
>
>
>
> Here’s the final rub, because the underlying data has so many
> inconsistencies that can only be made sense of with some regression models,
> it’s easier to “calibrate” the simulation model to the regression models
> than the original data. But I may use 2p monthly for gas, daily MVR for
> electric…
>
>
>
> So I need to ask if I have wondered completely off-piste with this!
>
>
>
> Chris
>
>
>
> *From:* David Eldridge <dancingdavide at hotmail.com>
> *Sent:* Tuesday, March 14, 2023 12:53 PM
> *To:* Jim Dirkes <jvdirkes2 at protonmail.com>
> *Cc:* chris.malcolm.yates at gmail.com; bldg-sim at onebuilding.org
> *Subject:* Re: [Bldg-sim] Lies, darn lies, and statistics
>
>
>
> Indirectly there probably isn’t a daily set of metrics in the Guideline
> since the simulation programs aren’t usually outputting daily results, but
> there’s no reason there couldn’t be one statistically.
>
>
>
> You could make one if you had only daily utility data and had to aggregate
> the simulation results to daily totals, there isn’t a published target
> metric but you could still show that you calculated one and why you think
> it was a good or bad result.
>
>
>
> DSE Mobile
>
>
>
> On Mar 14, 2023, at 6:10 AM, Jim Dirkes via Bldg-sim <
> bldg-sim at lists.onebuilding.org> wrote:
>
> 
>
> Dear Chris,
>
> Kudos for appreciating a gap in your understanding. (I'm in your camp)
>
>
>
> On the other hand, there are SO many variables in building operation that,
> short of a highly instrumented (and carefully calibrated) building for
> everything from lights to people to plug loads to HVAC - calibration is a
> fiction (and I'm confident that no such building exists). Daily calibration
> is a complete fiction, perhaps even a deception. On top of that, a
> "calibrated" model is just a moment in time; everything going forward is
> guaranteed to be different than during the calibration time period.
>
>
>
> I think of "calibration" as more like a sensitivity analysis - determine
> which variables matter more and which matter less. GenOpt works nicely for
> that purpose https://github.com/lbl-srg/GenOpt
> <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Flbl-srg%2FGenOpt&data=05%7C01%7C%7C0d63c1ff284443bc766608db247cc033%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638143890442545264%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=hMX7ISkjm6aByq3ZaUXf5p2QKTf3nlOBYbgP7ALodWQ%3D&reserved=0>
>
>
>
> Jim Dirkes  1631 Acacia Drive NW Grand Rapids, MI 49504 -  616 450 8653
>
> *Coffee Conversation:*
>
> The "individual" is an impossible concept, conceived by the Enlightenment
> philosophers. It makes no sense to the Christian. In marriages, and
> families, in associations and friendships and religious orders, we are not
> individuals, but a communion of persons.
>
>
>
> ------- Original Message -------
> On Tuesday, March 14th, 2023 at 6:52 AM, Chris Yates via Bldg-sim <
> bldg-sim at lists.onebuilding.org> wrote:
>
> Hi All
>
>
>
> I do find ASHRAE Guideline 14 a little too hardcore for my basic
> understanding of statistics. I can plug any of the equations into Excel,
> but I’ve realised my statistics understanding is very limited! (I’m outed!)
>
>
>
> We don’t actually have to work to G14 in the UK (probably good because my
> copy is a bit old). I finally realised I didn’t know enough after I’d been
> (lazily) using R2 in Excel on some monthly data. I thought that R2 > 0.9
> was generally ok… yeah, it wasn’t.
>
>
>
> So, are there any easy to understand resources available?
>
>
>
> I’ve been messing around with the IMT as well. It’s been fun going back to
> DOS 😊. This got me into daily methods, which leads to my next question.
> Is there any reason why there isn’t a daily calibration option specified in
> G14?
>
>
>
> Many thanks!
>
>
>
> Chris Yates
>
>
>
>
>
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