[Equest-users] Internal Loads: Internal Mass

[Nick Caton]

Hi Ross,

 

Rest assured, thermal mass properties of defined
envelope/partition/floor constructions *are* indeed tied up in those
construction definitions.  If you're taking the time to define your
envelope construction layers, then you've already done a pretty good job
of accounting for critical areas of the building's thermal mass.

 

Thermal mass inside spaces (i.e. furniture) is definitely one of those
variables you shouldn't have to think about (beyond the defaults) for
most projects, but it can grow into a pretty big deal in extreme cases.
The loads for a "greenroom" style enclosed pool might fluctuate pretty
wildly, requiring much larger heating/cooling equipment to avoid unmet
hours, if it weren't for the body of water acting as a thermal
"battery," tempering the temperature swings.  Other examples where
thermal mass could be critical to the model's behavior would include
aquariums, south-facing sunrooms, envelopes in arid climates with crazy
diurnal (night/day) temperature swings like Arizona, and in
earth-shelter ("half-buried") buildings/homes where the concept can be
taken to extremes as an energy saving feature (
http://earthshelters.com/free/chapter-1/).

 

In short: for most models, the interior furniture custom weighting
factor is not a huge deal, but in select cases it can be.  I would leave
it at defaults and keep it in the back of your head as a potential area
to troubleshoot/consider should you come across unmet hours or otherwise
inexplicable space load behavior.

 

~Nick

 

 

 

NICK CATON, P.E.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Ross
Farris
Sent: Thursday, June 02, 2011 4:48 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Internal Loads: Internal Mass

 

Howdy Y'all,

 

Wondering if anyone out there has attempted to look at the change in
simulation results if you start changing the internal mass properties
under the internal loads tab in version 3.64. I have always left these
as default because it seems fishy to me and I don't trust it. It would
seem that the floor weight should be accounted for when defining the
construction properties. Not sure why there would be two places to input
this information. I know that the density of furniture COULD have an
effect on the HVAC equipment's ability to maintain the desired
conditions in certain building types, but I don't know how much the
impact would be in the modeling world.

 

I know this is a feature that Energy Plus is attempting to perfect as
well, but quite frankly it all seems a bit bogus to me. In theory this
could make our models much more accurate if we spent the time to dial
everything in properly, but there are so many other features in eQUEST
to worry about that I don't want to waste my time with these categories
if they don't make the simulations more accurate. 

 

Any feedback from others experience would be appreciated. 

 

Thanks,

 

Ross Farris
Energy Analyst

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

________________________________

150 California Street, 3rd Floor
San Francisco, CA 94111
T.  415.398.7667 ext.4083  F. 415.398.0596
Thinking. Inside the building.

   <http://twitter.com/GlumacEngineers>  
<http://www.linkedin.com/company/34034?trk=tyah>         www.glumac.com
<http://www.glumac.com/>  
  <http://www.glumac.com/> 

 

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