RE: [EnergyPlus_Support] GrndTempCalc: building not temperature controlled

I tried to use slab with an unconditioned building and I could not get it to work very well. My slabs had a lot of solar gain due to large perimeter windows as well as large fluctuations in interior temperature. I had some recorded interior temperature data to calibrate my model. Things were ok for the winter with low sun angles, but ground heat loss kept the summers much cooler than the recorded conditions. Slab seems to always make heat flow to the ground when in this building the ground became a storage mass. To match a calibration, I had to iterate some ground temperature inputs that were closer to my summer interior temperatures. That works for my calibration but leaves me with a model that can’t be easily adapted to any interior condition changes.

Ned Lyon, P.E. (MA, WV)
Staff Consultant

SIMPSON GUMPERTZ & HEGER
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From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Wednesday, April 22, 2015 7:24 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] GrndTempCalc: building not temperature controlled

Danke Schoen,
In my case I have a passive solar building model so what are the initial indoor monthly average temps? Start out with the defaults for these fields (Jan: 18C, etc.). Should I use Slab.idf or my own building model?
What if I have multiple zones of unequal sizes?

I'm in Mongolia, the land of the blue sky and Chingis Khaan.

---In EnergyPlus_Support@xxxxxxxxxxxxxxx, <jeannieboef@...> wrote :

It's not the surface temperature of the inside of the slab. It is the monthly zone average air temperature. For example, if your building has heating only, you can run a first itteration simulation with a normal floor model (insulated) and see what your monthly average zone air temperatures are. In winter they will be at heating setpoint and in summer somewhat warmer. You then use those with the ground coupled model and again note your average monthly zone air temperatures of the zones in contact with ground. You can then update your inputs for a final or more itterations, as you see fit.

This has always been an itterative process. with the pre e+v8.3 slab and basement preprocess programs, my limited experience pointed to 3 itterations being "good enough".

Please think of the effect of the ground water level and its effect on monthly ground temperatures. In Berlin, we almost always build "in a swamp", so we have a pretty constant and cold ground temperature.

Mit freundlichen Grüßen- Sent from my iPhone (excuse the brevity)

i. A.

Jean Marais

b.i.g. bechtold

Tel. +49 30 6706662-23

On 22.04.2015, at 04:57, "bvonmoss@... [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

This statement in the doc was ambiguous to me:

"Field: TIN1 � TIN12 <month> Indoor Average tempperature set point
The next twelve fields specify the average indoor building set point temperatures for each month of the year. These fields are useful for simulating a building that is not temperature controlled for some of the year. In such a case, the average indoor set point temperatures can be obtained by first running the model in EnergyPlus with an insulated floor boundary condition, and then using the resulting monthly average zone temperatures in these fields."

"obtained by first running the model": Is this the slab model? or building model?
"average zone temperatures": Are these the TAverage (slab average temperature)? Or building zone temperatures.

My understanding is that it's the slab. You can't assign zone temperatures to ground zone temperatures except as the monthly indoor air temperatures.

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Posted by: "Edward G. Lyon" <EGLyon@xxxxxxx>

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