Large model modelling

Hello,

I have some doubts about modelling large models for an initial analysis (such a multistorey building of more than 2 storeys with more than 10 units for floor). There is some indications about some simplification? Floor and ceiling can be considered adiabatic (except the floor for the ground floor and the roof in the top floor?). Is it correct to model only some units (which one? In the corner? Where?)? Is it acceptable to consider adiabatic the wall between the units? The common corridor how can be simplified?

I have another question: if i need to model a ground to sky shaft, I need to model as a zone or can i leave a hole in the model?

Thanks,

fededea94

asked 2022-09-07 04:06:58 -0500

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Aaron Boranian

updated 2023-08-27 07:28:00 -0500

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Hi, the only limitations in DesignBuilder on model size are those of EnergyPlus, which as far as I know are not defined because they depend on the combination of model size and complexity. If you want to find out more about model simplification, which is unlikely be necessary except for very large or complex models, see our Help topic here: https://designbuilder.co.uk/helpv7.0/...

You will find lots of free guidance on modelling in DesignBuilder in our online tutorials here: https://designbuilder.co.uk/training/...

And more detail in our on-demand training here: https://designbuilder.co.uk/buy-onlin...

If you have a DesignBuilder license you can of course also ask our Support Desk for guidance.

I hope that helps!

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Dave

answered 2022-09-09 04:47:48 -0500

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Thank you, I tried to see the tutorial and sometimes I writed to the support desk, but the support desk of my country doesn't help too much because they made many consultancy and also for little doubts I must to pay.

fededea94 (2022-09-13 04:26:38 -0500) edit

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Basically IMO it very much depends on what the goal of your model is. Are you looking at/for "whole building information" or do you want to go into detail? In the first case, probably modelling the whole building works fine. In the latter case, increasing detail for a whole building model could prove difficult. E.g. if detailed solar control is of interest, it may be enough to model the south-west part of the building. You mention a ground to sky shaft - I am not sure, what you mean, however, if something is to happen in the shaft, e.g. stack ventilation, then you will need to model it via thermal zones.

I (also) hope that helps.

AGeissler

answered 2022-09-10 11:37:40 -0500

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Thanks you have clarified some doubts but I have more. Thats are my doubts, now I'm working on a prototype building (which is a 21 storey building) and my doubts are: 1)in this case is useful to do a whole building simulation without room but onyl with apartments to see the envelope gains? 2)can I choose some apartmens which are representative and simulate only these with semplification (.i.e. only one apartment in the corner and one inside with the wall to the other one adiabatic) to see the operative temperature and make a comfort evaluation?

Thanks

fededea94 (2022-09-13 04:25:18 -0500) edit

Again, what are you looking for in the end? For an apartment building with 21 levels, I would expect that 19 levels are practically identical in terms of layout. So, modelling one of these and then extrapolating will give good results, at least while using standard occupancy etc. and if there is no stack ventilation over the full building height involved. In terms of (thermal) comfort evaluations, what does the code of your country require? E.g. our code demands such a comfort evaluation based on rooms, so the apartment would need to be broken down into rooms (likely the southwest apartment).

AGeissler (2022-09-13 09:05:31 -0500) edit

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I'm not sure I can speak to the best way to model the ground to sky shaft, but regarding your other proposed simplifications for an initial analysis, they sound largely fine to me. Here are a couple of things I'd point out:

Modeling intermediate floors/ceilings as adiabatic seems reasonable as a first approximation as long as you think the surrounding areas will generally be kept at similar temperatures. For example, if they are all tenant units, this is probably a reasonable assumption (on average). If it's mixed commercial and you have different use cases, this may not be reasonable. I think the same goes for walls in between units.
Regarding which unit(s) to model, you can probably get away with modeling a subset of the units, just remember that the loads on a corner unit will look different than the loads on a central unit. And they also may look quite different based on solar orientation, depending on window-to-wall ratio, glazing characteristics, etc. So, if you really wanted to capture all of the variability, you would probably want to model eight units: four corners, and four internal units on each building side. I'm not sure how much this actually simplifies things, but it would perhaps save you a little time.