[Bldg-sim] Ot: Re: Modelling simplification for structural concrete columns

Chris Yates chris.malcolm.yates at gmail.com
Mon Mar 18 23:19:39 PDT 2013


Cheers Ed

I agree that the columns are unlikely to have a significant impact on the
energy model - even if they're quite big.

Bye for now

Chris

Sent from my Android device. Please excuse typos, etc.
On 19 Mar 2013 01:26, "Wealend, Edwin" <e.wealend at cundall.com> wrote:

>  Chris,
>
> I totally agree. Thermal bridging is an issue everywhere. My point was that in an energy model, the contribution of a thermal bridge to the overall energy mix of the building in hot climate will be much lower. You have to trust your facade consultant or architect has done his job!
>
> Regards,
> Ed
>
> Chris Yates <chris.malcolm.yates at gmail.com> wrote:
>
>
>  Hi guys
>
> Thermal bridges and interstitial condensation can be just as much an issue
> in hot humid climates as they are in cold. If there's am air leakage path
> past the pillars then humid exterior air might infiltrate layers.
>
> A bit off topic, sorry.
>
> Cheers
>
> Chris
>
> Sent from my Android device. Please excuse typos, etc.
> On 18 Mar 2013 03:36, "Patrick Bivona" <patrick.bivona at gmail.com> wrote:
>
>> Edwin, Graham,
>>
>>  Thanks for your advice. I had initially misunderstood what Joe was
>> actually proposing to do to take two dimensional conduction into account in
>> and in the vicinity of the columns. I'll follow his and your suggestion. It
>> will be a good learning experience for me anyway.
>>
>>  To answer your questions about the climate zone, this building is in
>> South Vietnam, so hot and humid all year around with some small variations.
>> The columns won't be insulated and the building will be air-conditioned. A
>> nice thermal bridge but not as bad as in a cold climate. Sadly, this is not
>> the type of project where the energy modelling is informing the design
>> much...
>>
>>  Regards,
>> Patrick
>>
>>
>> On 18 March 2013 09:25, Wealend, Edwin <e.wealend at cundall.com> wrote:
>>
>>>  Patrick,****
>>>
>>> ** **
>>>
>>> Those are some mighty columns! ****
>>>
>>> ** **
>>>
>>> I think it depends on what you’re trying to achieve with the model. If
>>> you’re looking at radiant temperatures, local thermal comfort or similar,
>>> then I would agree that taking an area weighted approach is going to
>>> neglect important local differences due to thermal inertia and other
>>> factors. However, if you’re looking at the energy use of the entire
>>> building, and it’s conditioned 24 hours, or in a climate with negligible
>>> diurnal swing, or with limited thermal mass generally, I would still say
>>> that a simplified approach would give you results that are accurate enough.
>>> I concur with Joe on the point about thermal bridging. Particularly if the
>>> remainder if the façade is insulated. Most construction inputs in energy
>>> modelling software don’t accurately account for thermal bridging, so if you
>>> think they’re going to be significant, then use a separate 2D calculation
>>> software and adjust your u-values appropriately. ****
>>>
>>> ** **
>>>
>>> That said, as they’re relatively large and it’s easy enough to divide up
>>> the walls into separate constructions, as it is with software like IES,
>>> then by all means model them separately and apply a different construction.
>>> ****
>>>
>>>
>>> Much of the importance of the above is also dependant on the climate
>>> your build is in. E.g. Un-insulated concrete columns in a northern European
>>> climate are a terrible idea and will come with a big energy penalty. In
>>> warmer climates, their contribution to the overall energy of the building
>>> will be much smaller and your efforts on the accuracy of their modelling
>>> may be better spent looking at something like the fresh air or building
>>> leakage.****
>>>
>>> ** **
>>>
>>> Regards,****
>>>
>>> Ed****
>>>
>>> ** **
>>>
>>> *Edwin Wealend*****
>>>
>>> Senior Engineer
>>>
>>> ****
>>>
>>> CUNDALL Hong Kong****
>>>
>>> 9th Floor Chinachem Johnston Plaza****
>>>
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>>>
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