[Equest-users] FW: Number of systems required by 90.1?

[Rosenberg, Michael I]

As stated Appendix G, 2007 requires one VAV air handler per floor for
baseline systems 5, 6, 7, and 8. In addition to the differences in
baseline fan power, the number and layout of the air handlers can have a
significant impact on the reset of supply air temperature which is also
a baseline requirement in Appendix G. 
 
Mike

__________________________ 

Michael Rosenberg 
Senior Commercial Buildings Energy Analyst 
ENERGY & ENVIRONMENT DIRECTORATE 

Pacific Northwest National Laboratory 
2032 Todd Street 
Eugene, OR 97405 
(541) 844-1960 
michael.rosenberg at pnl.gov 
www.pnl.gov 

 

________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of George
Hu
Sent: Wednesday, December 10, 2008 10:20 AM
To: 'Bill Talbert'; 'James Hansen'; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] FW: Number of systems required by 90.1?



It seems odd to me that 90.1-2007 requires the baseline building to have
one system per floor (system types 5, 6, 7 & 8).

These are all VAV systems, where you have individual VAV boxes
responding to different thermal zones. Why would different

number of AHU's in this case make a difference in heating and cooling
energy consumption?

In terms of fan energy, however, different number of AHU's may make a
difference. This is because 90.1 regulates

the fan brake horsepower, which is depending on the size of the fan
(Table G3.1.2.9, <20,000 cfm or >20,000 cfm).

For the same sized  building, assuming the total supply airflow being
roughly the same independent of the number of 

AHU's used, each individual fan's brake house power would be different
depending on its fan size, this may lead to 

different total fan energy consumption when you add all individual fan
energy up. For this reason, I would argue, it makes

more sense to keep the same number of AHU's in the baseline case as in
the proposed design, for you would then be comparing

"apple to apple", because the fan sizes in the proposed design would be
"comparable" to those in the baseline case.

 

George Hu, PE, LEED AP

President

AWE | Air Water Energy Engineers, Inc.

781.652.8688

www.awe-e.com

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bill
Talbert
Sent: Wednesday, December 10, 2008 1:01 PM
To: James Hansen; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] FW: Number of systems required by 90.1?

 

James,

90.1-2004 addendum u includes the 'one system per floor' wording for
systems 5 thru 8, but floors can be grouped when the thermal blocks are
similar. For LEED, it is optional to use addenda. 90.1-2007 adopts the
same wording.

Regards,

Bill 

 

 

Bill Talbert, PE, LEED(r) AP
Mechanical Systems

Phone: (608) 441-6677
E-mail: btalbert at aeieng.com

Affiliated Engineers Inc.
5802 Research Park Blvd.
Madison, WI. 53719
Tel. (608) 238-2616
Fax. (608) 238-2614


>>> "James Hansen" <JHANSEN at ghtltd.com> 12/10/2008 11:45 AM >>>

Thanks for your response Richard.

 

Can anyone confirm whether ASHRAE 90.1-2007 specifically says that your
Baseline model MUST have a system per floor?

 

I can't seem to find it in 2004, or the user's manual, or in the LEED-NC
reference guide.

 

GHT Limited
James Hansen, PE, LEED AP

Senior Associate

1010 N. Glebe Rd, Suite 200

Arlington, VA  22201-4749

703-338-5754 (Cell)

703-243-1200 (Office)

703-276-1376 (Fax)

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

 

From: Richard Ellison [mailto:REllison at southlandind.com] 
Sent: Wednesday, December 10, 2008 11:53 AM
To: James Hansen
Subject: RE: [Equest-users] Number of systems required by 90.1?

 

I interpret ASHRAE to suggest one should use 5 AHUs for just the reason
you mentioned.  They are different because of different exposures.  One
has slab and one has roof.  The external load would be different as
would the return plenum temperatures.  One might be able to group floors
2-5 energy wise but I recall reading, perhaps in 2007 where they
specifically meant on per floor for the baseline.  I always have at
least one AHU per floor in my baseline models.  Using only one AHU would
be cheating a bit.  This would be the same logic that says one must zone
rooms with different occupancies or schedules separately.

 

RICHARD ELLISON 
Energy Engineer 

Southland Industries

22340 Dresden Street, Suite 177

Dulles, VA 20166

Office: 703.834.5570

Direct: 703. 834.2438

Fax: 703.834.5572

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of James
Hansen
Sent: Wednesday, December 10, 2008 11:40 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Number of systems required by 90.1?

 

I'm working on a model of a 5-story building - my Proposed system is
floor-by-floor chilled water AHUs connected to a water-cooled chiller
central plan.  Airside is shutoff VAV boxes with hot water reheat.

 

For the size of the building, the baseline model is almost identical.
It is System 7 - Packaged rooftop VAV system with reheat boxes, chilled
water, hot water boilers.

 

My question is whether or not the Baseline model has to have a single
system for the building, or should it have 5 separate RTUs (doesn't
really make any sense) since my proposed building has 5 systems?

 

I'm pretty sure the answer is that the Baseline should just have one
packaged RTU for the building, but it actually makes a big difference on
energy use.  By breaking the systems down into one-per-floor, as is the
case with the proposed model, I end up saving a LOT of energy, possibly
because the 1st floor is slab-on-grade, and the 5th floor has a roof. 

 

Just wanted to make sure I have the correct number of "systems" for the
Baseline model.

 

Thanks!

 

GHT Limited
James Hansen, PE, LEED AP

Senior Associate

1010 N. Glebe Rd, Suite 200

Arlington, VA  22201-4749

703-338-5754 (Cell)

703-243-1200 (Office)

703-276-1376 (Fax)

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

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________________________________

The information contained in this communication is confidential, may be
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this communication or any part thereof is strictly prohibited and may be
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