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

[David Eldridge]

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
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------- 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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