[Bldg-sim] Above Grade External Wall Area Weighted U-value Calculation

Ralph Muehleisen rmuehleisen at anl.gov
Sun Sep 29 15:22:08 PDT 2013


ISO has a standard methodology for accounting for thermal bridging as
described in ISO 10221 and it is a standard part of using the ISO 13790
methodology for heating/cooling calculations.  ASHRAE has researched a
similar method which is described in ASHRAE Research Project 1365-RP
“Thermal Performance of Building Envelope Details for Mid- and High-Rise
Buildings”   I don't know if this is going to lead to an ASHRAE standard or
not.

That said, the ISO method is not a US standard and doesn't have ANSI or
ASHRAE equivalents,  Further,  I don't know of any specific code/energy
standard requirements to use the ISO standard.

Ralph T Muehleisen
PhD, PE, LEED AP, INCE Board Certified, FASA
Principal Building Scientist
Argonne National Lab
9700 S. Cass Ave, Bldg 221
630-252-2547, rmuehleisen at anl.gov


On Sun, Sep 29, 2013 at 3:02 PM, Joe Huang <yjhuang at whiteboxtechnologies.com
> wrote:

>  What the reviewer said is technically correct, but not often done in
> simple UA calculations because of the difficulty is calculating U-values
> for such thermal bridging.
> The effects can be substantial, especially for heavy-mass concrete
> construction. I've seen in China there's a standard method to account for
> thermal bridging in calculating wall U-values. Have not seen a similar
> technique for the US, don't know about the situation in Europe.
>
> Joe
>
>
> On 9/29/2013 9:31 AM, Sherif Farag wrote:
>
>  Dear All,
>
> I have submitted a project for review and received a comment requesting me
> to include the concrete slabs between floors (Not drop beams) in the
> External Wall' area weighted U-value calculation, the reviewer believes
> that concrete slabs acts as a thermal bridge and should be insulated from
> the outer side (The slab thickness), my understanding that concrete slab
> shouldn't be regarded as a part of the occupied area and therefore
> shouldn't be included in the area weighted U-value calculation.
>
> I would appreciate if you can advise on the above query!
>
> Thanks & Best Regards,
>
>
>
> *Sherif Farag*
>
> *Senior Sustainability Consultant*
>
> P.O. Box: 127842
>
> Abu Dhabi, UAE
>
> M: +971 55 199 0022 | E: sherif.sabr at gmail.com | Skype ID: sherif.farag9
>
>
>
>
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