[Bldg-sim] LEED Energy Model - 90.1-2004 Appendix G and Local Code

[Ulrik Welle-Strand Horn]

Dear Josh

There is in general no single answer to your question. The energy
performance rating method and Appendix G is concerned with establishing a
benchmark you can compare your building with. The benchmark is the baseline
building. As a benchmark building, there is no goal from a LEED perspective
to make this a quality building with the strictest building code possible
applied. Rather, the rating authorities seek to make it a standardized
benchmark to which all buildings can be compared, across all parts of the
world regardless of local standards. Other parts of the LEED certification
seeks to improve the quality of your building as much as possible, and
forces you to apply the strictest code possible, as you point out.

Generally, local code must be met in your baseline building if it is met in
your proposed building, but there are many exceptions. Appendix G first
states that the proposed and baseline building should be identical. Appendix
G then proceeds to describe the only ways you are allowed to let the two
models differ. This means that given that you are designing your proposed
building in accordance with local code, your baseline building will also
have to comply with this code except for the parameters which Appendix G
lets differ between the proposed and baseline buildings. There are therefore
times you will have to let your baseline model comply with local code, and
times where you do not have to. I am listing a few examples:

Cases where baseline building must comply with local code:

Many times, your baseline building must comply with local codes. For
instance if your local code forces you to limit vertical fenestration to 35%
of your building gross above-grade wall area, then this will also be the
case for the baseline building, in accordance with Table G3.1, No. 5 in
ASHRAE 90.1-2004. Another aspect of your baseline building that will have to
comply with local code is any regulation on dimensions. Appendix G clearly
states that the baseline building dimensions must be equivalent to the
proposed design in the same section as mentioned above.

Note also that the prerequisite of applying Appendix G is to comply with
sections 5.4, 6.4, 7.4, 8.4, 9.4, and 10.4 of 90.1. In at least one
instance, these requirements force you to apply local code (see section
6.4.3.8). I don't know these standards by heart, so you will have to read
through them and find out exactly where local code might be prescribed.

Cases where your baseline building does not have to comply with local code:

However, Table G3.1 lists parameters that will be different in the baseline
and proposed buildings. In these instances, if local code places
restrictions on lighting power, for example, then your baseline building
will not have to meet local standards. Instead, you will be rewarded for
complying with local regulations stricter than 90.1, as the baseline
building will have lighting power determined by section 9.2 of ASHRAE
90.1-2004.

Another example is if local code places restrictions on efficiencies of HVAC
equipment. In this case you model equipment in accordance with Appendix G
for the baseline building, which might be less stringent than local
requirements used in your proposed building. You will then be rewarded for
complying with local code as the energy consumption of the proposed building
will be lower than for the baseline building.

So keep in mind that in general baseline and proposed building should be
modeled identically. Then, let your baseline building differ only in the
ways stipulated by Appendix G, which sometimes allow you to let your
baseline building perform worse than what local code requires.

Good luck with your model and feel free to contact me for any further
clarification.


Sincerely yours,*


Ulrik Welle-Strand Horn *
Sustainability Engineer

*Silpa Inc.*
*s* i m p l e  .  *s* c i e n t i f i c  .  *s* u s t a i n a b l e
 AMERICAS | MIDDLE EAST | ASIA
www.silpainc.com

India: +91.90080.96083

On Wed, Oct 1, 2008 at 6:49 PM, Talbert, Joshua <jtalbert at hallam-ics.com>wrote:

>  Hello my Energy Modeling Friends:
>
>
>
> I had a question about defining the baseline with respect to a LEED energy
> model.  My local state code has a slightly more stringent energy code then
> 90.1 for our region, but I haven't found anywhere in LEED NC v2.2 that my
> baseline has to be defined with respect to my Local Energy code.  I know in
> other LEED credits that they require you to use the more stringent code when
> showing LEED compliance, but I can't find that same instruction with respect
> to defining the Baseline model per Appendix G.  Have any of you had
> experience with this, and can say whether I have to meet my Local Code with
> the baseline or just Appendix G?
>
>
>
> Thank you for your help and input.
>
>
>
> Sincerely,
>
> Josh
>
>
>
> Joshua W. Talbert, P.E., LEED-AP
>
> Hallam///ICS
>
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