Re: [EnergyPlus_Support] Re: Open plan office Zoning Guidelines for 90.1 G

Hi Xing,

I have to smile to myself when I read our discussion. I feel the same way as you do. Appendix G does not give enough trust to the modellers (but why should they). As for the experienced modellers, many of them can tell you what the large impacts are. Ironically, the biggest unknowns like people schedules, often have the biggest impact.

I've found that the size of the building is not as time consuming as the complexity. If you have multipliable zones, even floors, that will knock off a lot of time. Simple HVAC is another consideration. Simple or complex geometry (damn all those atriums and domes!!!) Unfortuanately, with LEED projects simple HVAC, and simple geometry is not happening often.

I've no experience with eQuest, but I had also learned that our competitors here in Berlin were modeling LEED projects in 25 days with TrnSys. So we bought TrnSys and guess what...it's possibly even more detailed than e+. They have 20 years worth of experience and have built up a substantial library of consolidated cases for easy adaption. If I had that for e+, maybe I would also be as fast. As I'm in Germany, (almost) every project I've seen has radiant ceiling/floor and a DOAS with VAV (no reheat). As such, using eQuest when I started was not possible.

When I first read the ASHRAE 90.1 norm, I was using e+ v3 and was wondering how any simulation program can do these simulations. For my first LEED simulation, I was pretty ambitious, and thought it would take about 2 months. It ended up taking 800 hrs (okay, it was a football stadium).

This discussion ties in closely to Jeremiah's post and should probably be continued there...

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Ã©?Â©Ã¦Ë?? <foolishstar@...> wrote:
>
> Dear Jean,
> I admit that it should model as each FCU or VAV box (with fan) as a separate zone. However, assume that a 20,000 m2 regular office building, how many thermal zones should there be? How long will the calculation time? I can hardly believe anybody would choose to use E+ to do the simulation. Because eQUEST can complete the mission in a much easier way and much shorter calculation time. I hope a study could be conducted to give a error analysis of the five zoning method and the "each fan each zone" method to illuminate how much of the zoning method will impact on the energy consumption. Then, a amendment coefficient could be given to largely reduce the repetition work.
> Xing
>
>
>
>
> At 2012-04-30 07:37:10,rfenergymodel <rfenergymodel@...> wrote:
>
>
> Thanks Sean and Xing for your reply. I have just dampers in my VAV boxes, reheat in some cases. I think I gonna go for combining "design" thermals zones according to loads similarity (perimeter orientation, core, etc)
>
> Best Regards
>
> Ric.
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jean marais" <jeannieboef@> wrote:
> >
> > The answere is: "it depends".
> >
> > I have it on pretty good authority (Expert for the EAp2 credit on LEEDuser, if I remember correctly...Christiaan Schaffer?) that energy consumers (like fans) should be explicitly modelled as is in your real design for the design case. If your baseline case VAV box has a local integrated fan then I would say you must model each one and the same goes for fancoils. For big repetitions look into using the eplus macro functionallity. As for thermal zoning, eplus can sometimes not apply multipliers to equipment, but can to zones. You could divide a large open floor into a multipliable zone with VAV and its portion of lighting, persons and other loads and simply apply a zone multiplier. Just take care to adjust the sizing (auto sizing) of the plant and airloop systems appropriately.
> >
> > If your VAV terminal box is just a damper, then sure, zone division as you described will do. Keep in mind the 15ft rule for the depth of the zone. And I believe you must use real room divisions in your zoning if you have planning for them.
> >
> > I've not opened my ASHRAE 90.1 in some time so feel free to correct me.
> >
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Frendior <rfenergymodel@> wrote:
> > >
> > > Hi,
> > > I'm modelling an office building for 90.1 Apendix G. Im a bit stuck with how much detail I have to model since the building is quite big. Do I need to zone the open plan office by dividing it into zones for each VAV box? Or can I just make one core zone, 4 perimeter zones (one for each orientation), plus one zone for combining unheated spaces (elevators, stairs, etc)?
> > >
> > > Thanks
> > >
> > > Ric.
> > >
> >
>