[Bldg-sim] Modelling simplification for structural concrete columns

[Michael tillou]

Hi Patrick,

Another choice is to use a tool like Therm to calculate the u-value of a typical section of your wall assembly and then create a uniform wall with that average u-value.  This is an acceptable strategy for a whole building energy model for LEED.  You can make it more complicated but it probably won't change the outcome unless you're also carefully calibrating the interior surface massing, furniture massing, interior surface reflectance and emittance values and using custom glazing performance data.

Most modeling software also has the ability to enter a window setback that will allow you to account for the shading of the column projections, or you can just add fins to the windows to pick up this shading effect.


Mike



Sent from my iPad

On Mar 12, 2013, at 11:36 PM, Patrick Bivona <patrick.bivona at gmail.com> wrote:

> Hi everyone,
> 
> I'm wondering how best to simplify a model when considering structural concrete columns.
> My modelling is in the context of the LEED whole building energy modelling. So I'm concerned with accuracy as much as acceptability by the LEED reviewers. I've read the ASHRAE 90.1 user's manual but didn't find a satisfactory answer.
> 
> Here's an example:
> 
>         ----
> wall   |    | wall
> -------|    |------
>        |    |
>         ----
>    concrete column
> 
> I can see 3 options for simplifying, each with its own issues:
> 
> 1. Make the external surface of the column at the same level of the surrounding walls and model the column surface as having its true thickness . The issue is that it alters the area of the space inside and doesn't account for the shading effect of the column.
> 
> 2. Follow the internal boundary of the column, which introduces 3 surfaces. Not sure what construction thickness to assign to these surfaces. This preserves the internal space area but alters the shading effect of the column.
> 
> 3. Follow the external boundary of the column. This also introduces 3 surfaces. Not sure what construction thickness to assign to these surfaces either. It preserves the shading effect of the column but alters the area of the internal space.
> 
> I'm leaning towards option 1. What do you think? Are they other better options I overlooked?
> 
> Of course, things get a bit more complicated when the walls either side are not aligned or in the same plan...
> 
> Thanks!
> Patrick
> 
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