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

Maria Karpman maria.karpman at karpmanconsulting.net
Fri Aug 17 11:12:31 PDT 2012

Karen and Bill,


One interesting caveat to this discussion is that ASHRAE definitions for
conditioned, unconditioned, and semi-heated spaces all apply only to
enclosed spaces, but definition of unconditional space included in 90.1
Section 3 suggests that garages should not be considered enclosed: 


unconditioned space: an enclosed space within a building

that is not a conditioned space or a semiheated space.

Crawlspaces, attics, and parking garages with natural or

mechanical ventilation are not considered enclosed spaces.


I like Karen's idea of modeling the same system type in the baseline and
proposed model for the garage. I would also look into using exceptional
calculations to claim credit for improvement in equipment efficiency, demand
control ventilation, and fan power relative to allowances in Table 




From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
Sent: Friday, August 17, 2012 1:43 PM
To: Karen Walkerman
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Baseline System For Semi-Heated Space for LEED




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.).




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? 






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



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


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





 <mailto:wbishop at pathfinder-ea.com> Description: Description: Image removed
by sender. Senior Energy Engineer 28Jun2012


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




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.








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