[Equest-users] area of (internal) partitions

Nick Caton ncaton at smithboucher.com
Wed Aug 4 11:19:31 PDT 2010


Filique,

 

This sounds a lot like a question I brought up when I was getting
started with eQuest and energy modeling in general:  What is "standard
practice" regarding where the inter-zonal and footprint boundaries are
defined, relative to actual wall thicknesses?  The quick answer is that
there aren't any hard/fast answers to this.  It was a good discussion
and is probably archived in [bldg-sim] if anyone cares to dig around...

 

In short:  

1.       eQuest areas correspond to the polygons used to define the
floor areas/building footprint.  These polygons are defined by the
shapes defined or traced from a CAD file in the wizards.  I'm pretty
sure (someone correct me if I'm wrong) the floor area taken up by
internal partitions (which have thickness) on the floor slab is NOT
subtracted from the total area, so if you double the thickness of your
internal partitions you will not see a change reflected in space areas.
This is normally not a big deal in the context of thermal modeled
behavior, but if you have many unusually thick partitions (1ft or more
deep), you might want to either account for them by modeling them as
unconditioned zones between spaces.  

2.       Regarding "best practice," here's a set of general guidelines
that would apply to various loads & modeling software packages (beyond
eQuest), prioritizing the interest of modeling with thermal accuracy:

a.       Define interior partitions using the midpoint between the two
surfaces.  This is generally not terribly critical - I will take small
liberties on this to reduce the number of vertices and simply actual
internal zones.

b.      Define the building footprint areas using the outermost surface.
This is more important as you want to accurately model the actual amount
of surface area subject to exterior loads.

c.       Define top of each zone (in the z-axis) using the top surface
elevation the respective floor or roof construction.

3.       On a related note, this ties into the general advice to not use
energy modeling programs with the intent to create perfect 3D
representations of your buildings.  If you need a pretty picture, they
make 3D modeling software for that purpose.  When it comes to building
geometries, simplicity is a virtue, and ASHRAE will even back you up on
that one (re: 90.1 User's Manual).  Avoiding overly-accurate building
geometries lets you spend more time modeling the more critical building
elements of a building's energy behavior (loads/systems/schedules/etc).

 

Best wishes,

 

~Nick

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of John
Aulbach
Sent: Wednesday, August 04, 2010 12:15 PM
To: Nijenmanting, F.C.; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] area of (internal) partitions

 

Filique:

 

Can you rephrase your question, please?  I don't understand how doubling
the size of your internal partitions decreases your floor area. The
eQuest floor areas are (to my undestandinding), from the outside of
outside walls to the "outside" of any internal partitions IN THE SPACE
THAT PARTITION RESIDES. You can have only one internal wall separating
two adjacent spaces.

 

Others may comment.

 

John R. Aulbach, PE, CEM

Senior Energy Engineer

________________________________

Partner Energy

1990 E. Grand Avenue, El Segundo, CA 90245
W: 888-826-1216, X254| D: 310-765-7295 | F: 310-817-2745

www.ptrenergy.com <http://www.ptrenergy.com/>  | jaulbach at ptrenergy.com
<mailto:%7C%20jaulbach at ptrenergy.com> 

 

 

________________________________

From: "Nijenmanting, F.C." <F.C.Nijenmanting at student.tue.nl>
To: "equest-users at lists.onebuilding.org"
<equest-users at lists.onebuilding.org>
Sent: Wed, August 4, 2010 12:15:19 AM
Subject: [Equest-users] area of (internal) partitions

Hello all,

I have a question about the area which is calculated by equest.
Does it take into account the width of internal partitions?
In reality, if I would double the size of my internal walls, my actual
floor area decreases.
But I could not find differences in the floor area calculated by Equest
if I change the thickness of my walls.

A similar question accounts for the external partitions. For drawing the
ground plan, should I therefore take the internal boundary, external
boundary or middle line?

Kind regards,
Filique
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