[Equest-users] LEED Baseline secondary HVAC system

[Bishop, Bill]

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

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

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

From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org]<mailto:[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<mailto: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<mailto:rkakati at dagherengineering.com>
www.dagherengineering.com<http://www.dagherengineering.com>

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