[Equest-users] External wall area for simulation

Nick Caton ncaton at smithboucher.com
Tue Mar 1 07:33:24 PST 2011


Hey Praveen,

 

I don't disagree your project's energy consumption would go up, but
probably moreso because you'd be correctly modeling the amount of
building envelope loads by matching the actual envelope area.  

 

Keep in mind you can reduce the conditioned spaces' floor area in
detailed edit (after the wizards) while retaining the defined exterior
surfaces.  There's nothing saying you have to deviate from either
reality.

  

Make sure the mass of your envelope wall construction is reflected as
you've defined it - I'd specify with layers.

 

If the minimum cost/magnitude of a desired photovoltaic array goes up
because that's the reality of the project... that's not a fault of the
model (or the modeler) - that's just reality ;).

 

~Nick

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: Praveen Jain [mailto:praveenjain83 at gmail.com] 
Sent: Tuesday, March 01, 2011 6:44 AM
To: Nick Caton
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] External wall area for simulation

 

Thanks Nick for good explanation.

Actually in my project we are using almost 2ft wide external walls to
get the effect of thermal mass. if I consider external wall area in
eQUEST model my area deviation is almost 4% and mismatch in conditioned
area is more than this. So project energy consumption would be more and
also not able to match TR for the project.
Actually we are also planning to go for 2.5% renewable energy credit, if
I consider external wall than PV cost would be more.

Can I exclude external wall area for eQUEST modeling ?

--
With Thanks and Regards
Praveen 

On Mon, Feb 28, 2011 at 10:02 PM, Nick Caton <ncaton at smithboucher.com>
wrote:

Hi Praveen,

 

I've copied below a discussion from some time back outlining my general
practice for "where to draw the line" when it comes to envelope/wall
boundaries.  This may be generally useful and seems to answer at least
part of your inquiry.

 

When I'm doing electrical and/or HVAC design alongside the model, my
area takeoffs for each inevitably will match up, because I hate doing
the same work twice.  

 

I use the outermost surfaces when defining my building footprint and
midpoints for all internal partitions for all calcs.  Space-by-space LPD
calcs in a strict reading do not require the space areas to be measured
to the outermost surface of an exterior wall (they do say to use the
midpoint of interior partitions, as of 90.1-2007).  I'd feel comfortable
saying the extra square-footage "handicap" I'm imposing on myself as a
lighting designer is an insignificant fraction in 99.9% of cases when
determining baseline LPD...   

 

Inevitably, areas summed for all spaces in a building between
architects, HVAC, and lighting designers will not match - that's a fact
of life and in my book that's okay, so long as nobody is way off.  Model
reviewers will inevitably/reliably gripe when the numbers don't match
exactly, and it's usually  an easy thing to either fix or explain after
the fact.  If you to try to make everyone use the same numbers from the
DD/CD design phases, you've chosen a losing battle.  For my part in the
role of the project's energy modeler, I'm satisfied to allow my fellow
designers do their own calcs, and just ensure nobody is way off along
the way... quibbles over small differences in the final tallies, if they
come up, are easy to reconcile.

 

~Nick

 

Error! Filename not specified.

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

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

 

From: equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] On Behalf Of Praveen Jain
Sent: Monday, February 28, 2011 3:37 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] External wall area for simulation

 

Dear All

 

While modeling in eQUEST should we include external wall area or not?

While creating single line diagram I exclude external wall and draw sld
on inner of external wall to match conditioned area.

But for lighting power density calculation ASHRAE 90.1 user manual
suggest to including external wall area. 

We are getting mismatch in area calculation for all HVAC, Lighting and
Architectural design sides.

 

Can anyone suggest what correct way of modeling in eQUEST ?

-- 
With Thanks and Regards,
Praveen K. Jain
Roorkee

 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Wednesday, August 04, 2010 1:20 PM
To: John Aulbach; Nijenmanting, F.C.; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] area of (internal) partitions

 

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

 

Error! Filename not specified.

 

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
<http://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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-- 
with regards,
Praveen K. Jain
Roorkee

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