Re: [EnergyPlus_Support] Best way to represent openings

Don't worry. You are asking good questions. If you were investigating something like a daylighting savings program requiring good simulation of indoor lighting levels for the photo sensors to be representative, then the full interior and exterior option is for you. As you are interested in an exterior roof, it is probably less important.

That being said, the user comfort can be better captured if you subdivide the zones as you have. In some situations, especially the placement of thermostats and zone HVAC this could be important.

Cross-mixing was the correct idea. Usually the amount is large and sufficient to ensure a well mixed zone(s).

I want to leave one thought with you:
Simulations are most powerful when they are comparing two identical models where one parameter varies. Then the urge to get very realistic models is less. The simulations will tell you A is better than B. This is where the programs are most powerful. This is "qualitive".

The next level is to ask 'how much better is A than B'. This is "quantitive". How exact the answer to this is depends on many large assumptions. And so the answer is more often than not quasi-quantitive in that you gain an idea of the magnitudes of the results. Many people forget that. We have to choose that right kind of investigation at the right time.

On 28 Sep 2015 6:38 pm, "sm.ibag@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

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Hi everyone, I'm new to all this building energy modeling thing and I've got some doubts while creating my model. I'm modeling a real building and my objective is to simulate a green roof on it and evaluate if this modification can reduce the total eletric consumption (decreasing the use of the ACs).
I thought I should use the FullInteriorlandExterior option, and for that I created all my spaces with a convex geometry. But, many rooms got split up in many pieces, so I assigned Air Walls for the 'openings'. I've read that it transforms it into a Drywall material, so the heat is transfered, but not airflow. So I thought of using the "ZoneCrossMixing" to allow that.
My questions are:
Should I really use the ZoneCrossMixing and Air Walls to represent this openings? That way I would let them be two different thermal zones.
Should I merge the two spaces into one thermal zone? I was really afraid of all the possible problems of using Internal Mass.
Is there really a huge difference in results between FullExterior and FullInteriorandExterior? Should I forget all of the above and just use FullExterior?
I'm sorry for all these subjective questions, I have just come to a dead-end, so I thought I could use an expert advice :)
P.S: before anyone questions, this simulation is part of my thesis, but I really wanted to make it as precise as possible, since the building being simulated is from the company I am currently an Intern in ;D