[BLDG-SIM] heating energy sources per Appendix G

gail gail22 at gmail.com
Fri Dec 15 14:11:44 PST 2006


It sounds like your building's systems will actually be penalized for having
the central heat.  Your proposed system is technically classified as a
"Fossil/Electric Hybrid", which means that it should be modeled using System
7 (VAV with HW reheat).  This means that your building would show a lot
higher energy costs in the proposed design because of the electric reheat.

A possible work-around is to classify the central furnaces as preheat.  This
seems to conform to the intent of Appendix G, though it may not conform to
the exact wording.  According to G3.1.2.3, if the HVAC system in the
proposed design has a preheat coil, and a preheat coil can be modeled in the
baseline system, the baseline system shall be modeled with a preheat coil
controlled in the same manner as the proposed design.

On 12/15/06, Aleka Pappas <APappas at enermodal.com> wrote:
>
> I'm having some moral issues calculating LEED energy reduction points
> per 90.1 appendix G for a project, and I'm wondering if someone else has
> had the same issue......
> This project has a packaged VAV with reheat system, with natural gas
> furnaces in roof top units, and electric reheat.  There's slightly more
> heating done by the electric reheat than centrally in this building.
> The way Appendix G reads, the Budget Building should have either all gas
> or all electric heat; all electric in this case (System 8).  Well, when
> I calculate energy savings relative to this Budget, the building is at
> about 20% energy cost reduction for 3 LEED points.  The savings are all
> from the central heating energy switch from electricity to gas, and is
> largely dependent on the cost of electricity relative to that of gas.
> It doesn't seem right to give this project such a high energy cost
> reduction, but I think this is what Appendix G is saying to do.  Anyone
> have any insight?  Is this addressed somewhere that I've missed?  I'm
> really wanting to put central gas furnaces in the Budget Building.....
>
> Thanks for your help,
> Aleka
>
> --
> Aleka Pappas
> Enermodal Engineering, Inc.
> Denver, CO
> tel: 303.861.2070
> fax: 303.830.2016
>
>
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