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Why is Large Office Prototype building so short?

asked 2016-06-06 10:14:19 -0500

lisang's avatar

updated 2016-06-06 10:23:52 -0500

The DOE Commercial Reference Building of the Large Office type was 47.6 m high. When I open the Large Office Prototype Building, in EnergyPlus and Google Sketchup, its height is only 37.5 m.

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answered 2016-06-06 12:08:02 -0500

updated 2016-06-06 12:57:46 -0500

The geometry created by the OpenStudio create_doe_prototype_building measure shows 37.5m: C:\fakepath\lrgoffc.png

However, since the middle floors are modeled with zone multipliers, does it really matter that the ground-level-to-highest-roof distance doesn't equal (number of floors) * (floor-to-floor height)? I would think unless the model includes objects that care about height above ground for calculating outdoor air conditions (e.g. ZoneVentilation:WindandStackOpenArea, which is not included), there will be no significant difference in the results.

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I think it does matter that the height is off since the "local wind" calculated by EnergyPlus will be different between 37.5 m and 47.6 m. From what I gather, this local wind affects (and local temperature) infiltration as well as external heat loss/gain calculations. If anyone can correct me, please do.

lisang's avatar lisang  ( 2016-06-06 12:16:45 -0500 )edit

Sure, wind speed and infiltration may be affected, but that same argument could be used against the use of zone multipliers in the first place, right? I would guess (I have no direct evidence for this) that the uncertainty of the infiltration and exterior convection models is greater than the effect that a 10m surface height difference will have on the load calculations. Which is probably why zone multipliers are used.

ericringold's avatar ericringold  ( 2016-06-06 12:34:17 -0500 )edit

PS the above is pure conjecture.. I'm sure you know more about the infiltration models than I do, @lisang :)

ericringold's avatar ericringold  ( 2016-06-06 12:47:24 -0500 )edit

I think you're right, that in the grand scheme of things, perhaps the difference of 10m in this case is not significant. Also, there are advantages in modeling and simulation time when using multipliers, especially really tall buildings. But in the case of airflow modeling, we model all the floors since infiltration will be different at each. Guess the real crux of my question is: "is the Large Office Prototype model wrong in its height, or should I go ahead with the 37.5 m height?"

lisang's avatar lisang  ( 2016-06-06 13:15:57 -0500 )edit

To the crux: the paper describing the Commercial Reference Building models shows 12 above-ground stories at 3.96 m floor-to-floor height, so the total ground-to-roof height should be 47.52 m.

ericringold's avatar ericringold  ( 2016-06-06 13:32:29 -0500 )edit

answered 2016-06-06 11:52:24 -0500

updated 2016-06-06 11:53:47 -0500

It's definitely 47.6m on my computer, taken from the start of the ground floor to the top of the building (excluding basement)


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That link is for the "Reference Buildings" and I agree, that is 47.6 m high. Another set of buildings, updated for newer energy standards called "Prototype" buildings (here) has a Large Office at is only 37.5 m. Am I reading the model wrong or missing something?

lisang's avatar lisang  ( 2016-06-06 12:07:25 -0500 )edit

I'd reach out to PNNL directly. There a contact info on that page leading to a helpdesk

Julien Marrec's avatar Julien Marrec  ( 2016-06-06 12:53:23 -0500 )edit

Thank you, I will contact them directly. I tried this forum first since it's members are very responsive.

lisang's avatar lisang  ( 2016-06-06 13:16:35 -0500 )edit

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Asked: 2016-06-06 10:14:19 -0500

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Last updated: Jun 06 '16