[Equest-users] LEED Baseline secondary HVAC system

[Nathan Miller]

Another weird off-shoot of this discussion is that I think *technically*
if your corridors have exterior walls, the baseline building constructions
and glazing properties for these areas should be based on the
non-residential envelope requirements of Table 5.5, because like retail
spaces, these are non-resi spaces per the previously discussed table
notes.

 

Of course in real life most projects will have the same wall assemblies in
the corridors as they do in the immediately adjacent apartments. This
probably doesn't come up much because corridors usually don't have much
exterior wall, but I wonder if anybody has ever seen that as a reviewer
comment? I had a recent project with a lot of corridors with exterior
walls, and I used the non-resi wall and window constructions, but I
haven't head back on reviewer comments yet. 

 

Nathan Miller, PE, LEED AP BD+C

Mechanical Engineer/Senior Energy Analyst

 

D 206-788-4577 | O 206-285-7100

 <http://www.rushingco.com/> www.rushingco.com

 

From: Bishop, Bill [mailto:bbishop at pathfinder-ea.com] 
Sent: Friday, August 17, 2012 11:24 AM
To: Nathan Miller; 'Maria Karpman'; 'Ritwik Kakati';
equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] LEED Baseline secondary HVAC system

 

Ritwik,

 

For better or worse, I agree with Maria that PTAC/PTHP should be applied
to the entire multifamily building. I disagreed with a LEED reviewer's
requirement that I separate a three-story dorm project into
residential/nonresidential portions. I mentioned the example of the User's
Manual case study that Maria described below, but I changed the baseline
anyway to keep from going back and forth with the reviewer. I complied
with the LEED reviewer's request by using System 3 per nonresidential zone
instead of System 1. What a waste of time for negligible energy impact.

 

If you feel compelled to model additional system types for nonpredominant
conditions, I guess you use System 3 or 5 based on the floor area.

 

Regards,

Bill

 

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

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nathan
Miller
Sent: Friday, August 17, 2012 1:13 PM
To: 'Maria Karpman'; 'Ritwik Kakati'; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] LEED Baseline secondary HVAC system

 

It kind of falls in that grey-area of whether you get to CHOOSE to apply
the exceptions listed in G3.1.1 or whether  you SHOULD apply them if they
are applicable to your project. 

 

The emphasis the in following excerpts is mine. 

 

G3.1.1 exception a states: "Use additional system types for
non-predominant conditions (i.e. residential/nonresidential, or heating
source).

 

The same footnote you reference in table G3.1.1A states "Residential
building types include dormitory, hotel, motel, and multifamily.
Residential space types include guest rooms, living quarters, private
living space, and sleeping quarters. Other building and space types are
considered nonresidential.

 

To me it feels like exception a says use additional system types for
non-resi spaces, such as retail or corridors because they will have
different loads and operational hours, though I can see your point as
well. 

 

I've never had a LEED reviewer tell me to use PTAC/PTHPs for corridors,
but I'd be willing to bet others have used these systems for corridors and
also not received comment on them.

 

Nathan Miller, PE, LEED AP BD+C

Mechanical Engineer/Senior Energy Analyst

 

D 206-788-4577 | O 206-285-7100

 <http://www.rushingco.com/> www.rushingco.com

 

From: Maria Karpman [mailto:maria.karpman at karpmanconsulting.net] 
Sent: Friday, August 17, 2012 9:07 AM
To: 'Nathan Miller'; 'Ritwik Kakati'; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] LEED Baseline secondary HVAC system

 

I would argue that residential system type (PTAC/PTHP) should be applied
to the entire multifamily building. The heading of the first column in
Table G3.1.1A is Building Type, not Space Type. The note below the table
reads "Residential building types include dormitory, hotel, motel, and
multifamily..".  If the baseline HVAC should be determined solely based on
the conditioned floor area and number of floors of residential versus
non-residential spaces, then why was the building type used as column
heading and in the note below the table? A case study in 90.1 User Manual
involves a building with 4 multifamily and 4 non-residential floors. The
4-storey 54,000 SF non-residential portion in the case study is modeled
with System 5, and the 4 residential floors are modeled with PTACs. If
corridors/stairwells in multifamily buildings are modeled with
non-residential baseline HVAC, then  most multifamily buildings over 5
floors would have System 7 serving these areas. I agree with Nathan that
it doesn't makes much sense, especially since most of these spaces are
indirectly conditioned by losses through interior walls of apartments. 

 

Maria

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nathan
Miller
Sent: Friday, August 17, 2012 11:32 AM
To: 'Ritwik Kakati'; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] LEED Baseline secondary HVAC system

 

Based on the exact wording of the Table G3.1.1A, I would say you are
System 7, which is for "Nonresidential and more than 5 floors OR >150,000
SF. However, we all can see that it is probably a pretty ridiculous
baseline system for a corridor ventilation unit.

 

On multifamily projects I've worked on, I've used system 5 in the past
(even though the floor number requirement would trigger system 7) and
never been called on it. That being said, usually that was on projects
with ~7 stories, so I was much closer to the threshold, so maybe the LEED
reviewer just let it slide. Even System 5 is a bit peculiar for a corridor
unit. At least in my climate they end up usually being packaged rooftop,
constant volume units. 

 

Nathan Miller, PE, LEED AP BD+C

Mechanical Engineer/Senior Energy Analyst

 

D 206-788-4577 | O 206-285-7100

 <http://www.rushingco.com/> www.rushingco.com

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Ritwik
Kakati
Sent: Thursday, August 16, 2012 2:09 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] LEED Baseline secondary HVAC system

 

I am modeling a residential building under LEED 2009. With reference to
ASHRAE 90.1-2007, Exception 'a' in section G3.1.1 which states that we
should use additional system types for nonpredominant conditions if they
apply to more than 20,000 SF of conditioned space - I am confused which
system type I should use for my corridors and other non-residential
conditioned spaces, which are about  21,000 SF total, spread across 20
floors. Do I use System 7, because my non-residential spaces are located
on more than 5 floors, or use System 3 or 5 because the area is less than
25,000 SF?

 

Thanks,

 

Ritwik Kakati, LEED Green Associate

Design Engineer

DAGHER ENGINEERING, PLLC

29 Broadway, New York, NY 10006

T. 212.480.2591 x140

F. 212.480.2654

rkakati at dagherengineering.com

www.dagherengineering.com

 

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