[Bldg-sim] Where should you choose your wall location forsimulations, inside, outside or center of wall

[Nick Caton]

My practice with all load calculation/energy modeling software has been:

 

All floors/roofs: Top of surface

Exterior glazing/walls: Outermost surface

Interior walls/partitions:  Center of construction

 

I know this is the advice offered by IES-VE's support staff, but that
doesn't mean all modeling engines behave the same.  As you may gather,
I've always assumed energy modeling and HVAC load calculation models
"subtract out" the thickness of constructions from calculated space
volumes.  I don't know whether this is a "universal standard practice"
between software packages / modeling engines.

 

Since I would ultimately much rather slightly oversize than undersize an
HVAC system, I'm of the mindset that the potential for a little extra
surface area / conditioned space would if anything bump my results in a
desired, conservative direction regarding space loads.  If absolute
accuracy is your goal, then in lieu of a "universal standard," I'd
imagine you would have to ask the developers/users of the specific
program you're using at the moment to determine its true behavior in
this regard.

 

~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: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Ryan Del
Balso
Sent: Friday, September 11, 2009 11:50 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Where should you choose your wall location
forsimulations, inside, outside or center of wall

 

Are there standard practice recommendations for where to place your wall
for a simulation?  Knowing every wall has thickness, but the simulation
engines are generally just using no thickness walls with a calculated
U/R value, where should you define your walls for the simulation?
Should they be defined at the exterior face of the wall, the interior
face or the center of the wall.  It seems the exterior face can greatly
increase the zone volume, thus incorrectly determining the energy usage,
but the interior face underestimates the exterior exposure of the wall.
The center of wall seems a good compromise, but is difficult to identify
and draw.  

 

For interior walls/zone delineation the same question applies.  From an
energy standpoint is it better to place the zone boundary on the face of
the higher load zone or the lower load zone or split the difference?

Thanks for any advice or direction to standard practices.

 

 

 

 

Ryan Del Balso

Building Performance Engineer II

ryan at ambient-e.com

130 W. 5th Avenue, Denver, CO 80204 

t 303.278.1532x210 | f 303.278.8533 |

ambient-e.com <http://www.ambient-e.com/> 

 

 

 

 

 

 

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