Significance of wall orientation

Replies to This Discussion

Permalink Reply by Theodoros Galanos on May 6, 2015 at 5:08am

Hi everyone,

Sorry for being away, been kind of busy.

Mostapha, I will try and email the model the coming days. The tricky part is that I can't really share it online due to confidentiality issues.

I did however run into a similar problem in another much simpler model.

How on earth should I model simple, low-rise appartments? The floor layout changes from level to level. I ended up breaking up the floor/ceilings every time I added a level to the model. Resulted in a pain in the ass modelling process and similar azimuth errors. However, this time I feel it's because of me.

Is there a better way to simulate this? I know intersect masses does this (from Chris's video tutorials) but if I'm not mistaken in that case it was breps and not honeybee zones. There must be a better work flow however :(

Also, stupid question, what do we do with floor/ceilings. I mean since I am supposed (I hope I've been understanding Mostapha correctly in this whole post) to use the same surface as floor and ceiling between two levels, can I change orientations without internalizing? Or do I need to internalize?

Sorry for the mess of questions. I'm attaching the model. I internalized all the breps in one of the two buildings (LEFT).

Kind regards,

Theodore.

Attachments:

• TypeC.gh, 1.4 MB

Permalink Reply by Theodoros Galanos on May 6, 2015 at 7:36pm

After reading this https://unmethours.com/question/2336/what-is-the-difference-between... I am even more confused and even more certain it was my modelling fault.

Does this mean I need to duplicate the surfaces? Is a flip on the brep enough or do I need to create a new surface? Or is this that Honeybee handles by itself (i.e. the normals)?

Kind regards,

Theodore.

Permalink Reply by Theodoros Galanos on May 6, 2015 at 9:12pm

Hi again,

Sorry for the onslaught of messages. I managed to run the simulation with no severe errors when I input every floor's solve adjacencies separately in the energy plus component. I imagine the results are a bit compromised like this but it at least tells me the errors are between the floors, so in the way I set up floors and ceilings.

Thanks in advance.

Kind regards,

Theodore.

Permalink Reply by JPE on May 7, 2015 at 12:08am

Theodore –  To answer your initial question "is interior wall orientation crucial to energy simulation in multi-zone models?”. Answer: Yes, very.

EnergyPlus needs to know what bounds each thermal zone and which side of the surface “outside” is, and E+ knows this by the order vertices are entered.  E+ requires surface normals to be oriented uniformly (facing outwards, away from the individual zone volume) and all thermal zones need to be fully enclosed, defined by its own set of surfaces.

 

Therefore, a two zone model with a shared wall requires the dividing wall (ceiling/floor) to be defined for each zone independently.  Although these surfaces will have the same x,y,z coordinates and occupy the same plane, E+ will see them as boundaries defining each individual zone so wall assemblies can be applied and the energy transfer calculated correctly.  Omitting one shared plane will result in E+ throwing errors at you.

 

Taking this a step further: if a ceiling in thermal zone Z1, has a thermal zone above it (Z2) that occupies only a portion of the total surface area of the ceiling, with the remaining area as a roof, the “outside” boundary conditions for Z1 ceiling varies (part is a ceiling/floor of Z2 and the other is ceiling/outside) and E+ needs to know this by dividing the ceiling surface accordingly.  Thus your ceiling of Z1 will need to be made of two planes one that relates to the floor of Z2 and one that is ceiling/roof material.  In other words; when adjacency conditions of a zone’s surface changes, E+ needs to be informed of this condition by defining a new surface.

It may be too late in the night to try to write technical explanations, so I hope this explanation helps clarify rather than confuse.

 

Cheers

Permalink Reply by Theodoros Galanos on May 7, 2015 at 12:16am

Hi JPE,

Thank you very much for your response, helps clarify things a bit. The articles I've been reading state similar strategies.

I want to say that I did follow this in my model (hopefully). The way I understand it, in Honeybee, I need to manually breakdown the surfaces that account for ceiling/floors when the floor plan between levels changes. I believe I did that in my model. However, I was not sure (and still not sure) if Honeybee handles the assigning this "outside" automatically between zones after the zones have been set on per-surface level.

That said, I realize now that I have both exposed floor and exposed ceilings in my model which I wrongly grouped together with all the other floors and ceilings. I will try to remedy that. But given the error log from E+ I think that I have boundary issues in most if not all interfaces between levels (even after I correctly assigned the normals).

As I sad in the previous post, not solving adjacencies between levels and simply dragging each solve adjacency output from each level allows me to run the simulation without the fatal errors, but I have to wonder on the validity of my results.

Kind regards,

Theodore.

Permalink Reply by JPE on May 7, 2015 at 12:48am

Theodore -- The severity of E+ errors can have varying effects on results, so live by the mantra “garbage in = garbage out” when working with energy simulation tools and always clean up your model!

 

Some minor errors simply state that a mathematical impossibility occurred in the calculations, for example, that the RH point dropped below zero.  While other errors signify major issues that need to be addressed before any results are to be trusted.  Adjacency errors, although not fatal, need to be corrected.  For more detailed help with specific errors try the E+ support group over on Yahoo Groups : https://groups.yahoo.com/neo/groups/EnergyPlus_Support/info

Cheers -- J

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