[Bldg-sim] 90.1 appendix G Baseline System interpretation

[Rut Wattanasak via Bldg-sim]

David,

I was just looking into a very similar scenario this morning in fact. I
have one question and some follow-up comments as well.

You stated that exception G3.1.1a can be applied, does the non-predominant
conditioned space total to be at least 20,000 sf?  If so, shouldn't the
residential baseline (system #1) be used for all residential units
(according to Table G3.1.1A), and not system #3 as you stated? Also in this
case, the whole baseline building should be fossil fuel heat source - check
LI 10132 that discusses baseline heat source selection, if you're doing
this for LEED.

The next step would be to determine the commercial space baseline, based on
the floor areas of the first two levels. You might end up with System #3 or
#5 depending on the total area of the commercial space. At least that's how
I read "ASHRAE Interpretation IC 90.1-2007-05", you can search the quote to
find the document. I'm not sure if there's anything else that supercedes
that interpretation since.

To put it simply, if exception a applies, then I'd personally model the
upper 3 floors using system #1 and the lower 2 floors with either #3 or #5
based on total commercial space area. That's how I interpreted those two
referenced resources.

Thanks,




On Fri, Aug 26, 2016 at 1:35 PM, David BRADLEY via Bldg-sim <
bldg-sim at lists.onebuilding.org> wrote:

> Colleagues,
>
>   I am working on a 90.1 Appendix G model of a 5-story mixed-use building.
> The bottom two floors are commercial spaces, the top 3 floors are
> residential. There is an underground parking garage as well, which I have
> considered to be part of the residential use). The building is heated by a
> combination of gas and electricity; gas use predominates. By floor area the
> building is predominantly residential. However, about 62% of the building's
> total energy use is associated with the commercial parts. Because of the
> way that energy use breaks down I am leaning toward considering the
> building to be non residential, using System 5 as the baseline and taking
> exception G3.1.1 a (system 3) for the residential spaces. If anyone has
> experience with such buildings and could share their thoughts on the
> validity of my interpretation, I would greatly appreciate it.
>
> kind regards and my thanks in advance
>
>  David
>
>
>
> --
> ***************************
> David BRADLEY
> Principal
> Thermal Energy Systems Specialists, LLC
> 22 North Carroll Street - suite 370
> Madison, WI  53703 USA
>
> P:+1.608.274.2577
> F:+1.608.278.1475
> d.bradley at tess-inc.com
>
> http://www.tess-inc.com
> http://www.trnsys.com
>
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