[Bldg-sim] Baseline System For Semi-Heated Space for LEED

[Bishop, Bill]

Karen,

I'm not convinced it makes sense to break out the heating capacity into ventilation and non-ventilation. I would include the total heating capacity of all units serving the garage to determine if it falls under the 3.4 Btu/h-ft2 threshold per the semiheated space definition. If you still think it is a semiheated space then I think you could model the baseline and proposed with identical HVAC systems and consider it process energy. Garage ventilation should probably be considered process energy either way, as it is not just for meeting minimum occupant-based ventilation. If it ends up being a conditioned space, you should be able to apply a System 3 or 4 to the baseline per the other G3.1.1 exceptions (different process loads or schedules, code-required minimum circulation rates, etc.).

Bill

From: Karen Walkerman [mailto:kwalkerman at gmail.com]
Sent: Friday, August 17, 2012 1:17 PM
To: Bishop, Bill
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Baseline System For Semi-Heated Space for LEED

Thanks Bill.  I didn't realize 90.1-2010 gave a little more info on this topic.  The space is actually pretty large, and doesn't fall under one of the types you listed in ASHRAE 90.1-2010.  It's a maintenance/garage area and has less than the required btu/sf for space heating (but some additional capacity to to temper ventilation air).  There is additional capacity to make up for outdoor ventilation air, so not modeling the energy use would be a mistake, I think.  What do you think about modeling the HVAC systems for the spaces identically in the baseline and proposed?

--
Karen


On Fri, Aug 17, 2012 at 9:16 AM, Bishop, Bill <bbishop at pathfinder-ea.com<mailto:bbishop at pathfinder-ea.com>> wrote:
Karen,

A "semi-heated" space is not a "conditioned space" per ASHRAE 90.1. For a LEED/Appendix G model, the baseline system type is based on conditioned floor area, and the requirement for modeling heating and cooling applies to conditioned spaces only. You could model the space as unconditioned in the baseline and proposed models, and capture the semi-heating as neutral process energy.

Alternatively, you could use System Type 9 or 10 from ASHRAE 90.1-2010. Systems 9 and 10 apply to "thermal zones designed with heating only systems in the proposed design, serving storage rooms, stairwells, vestibules, electrical/mechanical rooms, and restrooms not exhausting or transferring air from mechanically cooled thermal zones in the proposed design" per G3.1.1 Exception e. The ASHRAE definition for "zone, HVAC" is "a space or group of spaces...", not "a conditioned space...". So I think you could apply System 9 or 10 to a semi-heated space, if the space type is one of those listed.

Either of these options should be easy enough to change/undo if a LEED reviewer disagrees with your approach.

Regards,
Bill

[Senior Energy Engineer 28Jun2012]<mailto:wbishop at pathfinder-ea.com>

From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org>] On Behalf Of Karen Walkerman
Sent: Thursday, August 16, 2012 8:36 PM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] Baseline System For Semi-Heated Space for LEED

Hi,

I have a space that meets the requirements of a "semi-heated" space.  Question is - how do I model the baseline system?  I have found no information in AppG, LEED, or any other resources.

Thanks,

--
Karen

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