[Bldg-sim] Modeling existing buildings per LEED EAc1 / App G

[James Hansen]

Hello,

 

I asked a question a few weeks ago about whether or not you have to rotate the Baseline building in a LEED-NC EAc1 calculation (or Appendix G calculation for some other reason).  Thank you everyone for your replies (see below)...it appears that yes, you do need to perform the four (4) separate runs for each direction.

 

However, I have a more general question about modeling renovations to existing buildings.  According to the LEED-NC reference guide, you are to model the Baseline building (if it is existing) with the same "thermal parameters" as the existing building.  Appendix G, Table G3.1 Section 5f) says that "For Existing building envelopes, the baseline building design shall reflect existing conditions prior to any revisions that are part of the scope of work...".  

 

Futhermore, the reference guide goes on to say that "For projects served by existing HVAC systems, such as a central plant on a campus, Section 10(a) of Table G3.1 states that when there is an existing HVAC system, the model shall reflect the actual system type using actual component capacities and efficiencies."

 

But this section is actually under the "Proposed" column, and I can't find anywhere where it specifically says that the Baseline system should be modeled as the existing building currently stands.

 

So I have two questions:

 

1)       If you have an existing building, is the HVAC system supposed to be modeled as it currently exists in the Baseline model, as well as things like the thermal parameters, etc?  What about the lighting?  If you have an existing building that you KNOW has a lighting density of 2.0 Watts / sq ft pre-retrofit, is that how you should model the Baseline building?

 

2)      If I have an existing building that happens to have one exposure with NO windows, and part of the renovation is to install windows on that side of the building, while STILL BEING BELOW 40% total window area.  How do I model the baseline building?  With windows there or not?  If not, then that is a major penalty, and in reality, I may want to compare my Proposed building to a Baseline model that is 90.1-2004 compliant.  Can you even do that if it is an existing building?  Can you choose whether to model the Baseline building it as it exists, or model it per minimum ASHRAE standards?  

 

I haven't yet received a copy of 90.1-2007.  Does Appendix G in that version clarify any of this?  

 

Thanks in advance!

 

James Hansen

GHT Limited

703-243-1200


________________________________

From: bldg-sim-bounces at lists.onebuilding.org on behalf of Dakota Kelley
Sent: Wed 10/22/2008 4:15 PM
To: Kevin Kyte
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Building rotation per Appendix G



Kevin,

I have since reversed my stance; Eric O'Neill was kind enough to provide
me with the following link:

http://lists.onebuilding.org/htdig.cgi/bldg-sim-onebuilding.org/2007-Nov
ember/005709.html

I had not come across this thread before, and it sounds like existing
buildings need to be rotated regardless of the situation.

Dakota

-----Original Message-----
From: Kevin Kyte [mailto:kkyte at robsonwoese.com]
Sent: Wednesday, October 22, 2008 3:00 PM
To: Dakota Kelley; JHANSEN at ghtltd.com
Cc: bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] Building rotation per Appendix G

What if it is an existing building and there have been alterations to
the
floorplan?

-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Dakota
Kelley
Sent: Wednesday, October 22, 2008 3:16 PM
To: JHANSEN at ghtltd.com
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Building rotation per Appendix G

James,

It is my understanding that it is not necessary to do the rotation on an
existing building.  I am also working on an existing building, and I
plan to submit without rotating.  This topic has been debated on the
forum in the past with opposing opinions, each side having reasonable
arguments, but if my memory is correct the best/last argument was that
existing buildings do not need to be rotated.  I think this position
makes more intuitive sense, too.

I don't believe a definitive resource exists for this question, which is
why I plan to "learn the hard way" on my project.  I have heard that
2009 LEED revisions will address questions specific to existing
buildings; hopefully this will be one of them.  In the interim, I would
ask that anyone with a differing opinion specify the resource guiding
them.

Dakota Kelley
Telios Engineers

-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of
bldg-sim-request at lists.onebuilding.org
Sent: Wednesday, October 22, 2008 2:02 PM
To: bldg-sim at lists.onebuilding.org
Subject: Bldg-sim Digest, Vol 11, Issue 20

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Today's Topics:

   1. Building rotation per Appendix G (James Hansen)
   2. About weather data files (M F A Ramadan)


----------------------------------------------------------------------

Message: 1
Date: Tue, 21 Oct 2008 17:15:28 -0400
From: "James Hansen" <JHANSEN at ghtltd.com>
Subject: [Bldg-sim] Building rotation per Appendix G
To: <bldg-sim at lists.onebuilding.org>
Message-ID:
       
<25F2BDB6656B8F40A1289ED906D6B5CF038E117F at EXCHANGE1.cadd_group.ghtltd.co
m>
       
Content-Type: text/plain; charset="us-ascii"

I'm working on a project where I am pursuing LEED EAc1 for an existing
building.  As I understand it from the LEED-NC reference guide, as well
as from some snippets of 90.1, I actually model the baseline building as
is currently exists.  The reference guide says:

"For existing buildings that are being renovated, the building envelope
design parameters for the Baseline Design should be modeled using the
existing (pre-retrofit) building envelope thermal parameters rather than
the ASHRAE 90.1 prescriptive building envelope requirements for the
specified climate."

So I'm using actual window areas, actual insulation values, etc.

My question is:  if I'm using this exception, do I also no longer have
to do a simulation at the four different azimuth required by the LEED
EAc1 template?

I find 90.1, as well as the user's manual, fairly lacking in describing
how to apply Appendix G to existing buildings in general....

Thanks in advance!

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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