[Bldg-sim] differences between energy simulations programs

Wed Mar 24 12:40:26 PDT 2010

You need to have some mechanism for passively charging your mass to really
get the major energy benefits of the mass.  If you have a building that's
being actively heated and cooled all the time, with no passive inputs, then
the mass won't do much except reduce your peak thermal load some, provided
you get an actual temperature differential between the mass and the space
(i.e. the system is sized correctly and the space temperature exceeds the
typical set point at the peak hour).

So, you can couple passive solar input to your mass, and use that mass to
sink heat for later (rather than having the space temperature rise).  The
passive solar input to the space has to be higher than the thermal load on
the space for a while to get in energy benefit from the mass storage.  Or
you can use passive night cooling to cool your mass for later.

There are many situations where a building would not be able to take
advantage of mass, so anecdotes of one particular building model not
realizing savings from increased proves that not all buildings will see
improvements with increased mass, not that increased mass has zero savings
in all cases.  My personal experience in modeling mass shows that mass
makes a huge difference in the efficacy of passive heating and cooling
strategies.  I think this paper talks about some of what we found:
http://www.ibpsa.org/proceedings/BS2007/p120_final.pdf

On Wed, Mar 24, 2010 at 10:29 AM, Shaun Martin <
smartin at shaunmartinconsulting.com> wrote:

> Hi Paul,
>
> My experience on EnergyPlus with this question led me to the conclusion
> that
> the time-delayed release or gain of heat in interior concrete walls or
> floors is a bit of a fiction.   Virtually all of this heat is picked within
> the first hour by the mechanical systems.   Exterior concrete, likewise,
> had
> very little impact on the occupant comfort and interior temperatures simply
> because of the presence of insulation.   However, remove the cooling
> systems
> (we do that here in Canada, particularly in residential high-rises) and the
> picture is very different.
>
> It would be interesting to repeat the same analysis on a building that is
> fully designed to take advantage of passive heating and cooling. Few are,
> of
> course. I suspect even partially passive buildings (mixed/hybrid mode)
> don't
> experience even a fraction of the purported benefits of thermal mass.
>
> The increase in the heating load is because the assembly is treated as one
> R-value. Removing the carpet decreases the R and increases the heating
> load.
>
> Shaun
>
> Shaun Martin LEED AP
> Principal
> Shaun Martin Consulting
> Suite 200 - 420 West Hastings Street
> Vancouver, BC   V6B 1L1
> c: 604-789-1095
> e:smartin at shaunmartinconsulting.com<e%3Asmartin at shaunmartinconsulting.com>
> member CAGBC, ASHRAE
>
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul Grahovac
> Sent: Wednesday, March 24, 2010 8:36 AM
> To: Eurek, John S NWO; Peterson, John (EYP/HP CFS);
> bldg-sim at lists.onebuilding.org
>  Subject: Re: [Bldg-sim] differences between energy simulations programs
>
> FYI, another comment on TRANE Trace 700:  the modeling engineers I hired
> told me, after consultation with TRANE, that exposed interior concrete
> floors, when modeled against the ASHRAE baseline of carpeted floors, showed
> a reduction in the cooling load, but an increase in the heating load.  An
> increase in the heating load was contrary to my reading in passive solar
> books.  I used a simplified simulator for lay people, and it showed exposed
> interior concrete floors improved cold-weather performance over carpeted
> concrete (HEED, www2.aud.ucla.edu/heed).
>
> I have since heard that TRANE does not model thermal mass well.  I have
> also
> not been able to find anyone with experience modeling the thermal mass of
> interior exposed concrete floors using any simulation tool.
>
> Paul Grahovac, LEED AP
> PROSOCO, Inc.
> 785-830-7355
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Eurek, John S
> NWO
> Sent: Wednesday, March 17, 2010 3:32 PM
> To: Peterson, John (EYP/HP CFS); bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] Discrepancy between Equest & Trace 6.2
>
> John,
>
> It is like buying a car.  Do you want a truck, manual/automatic, something
> fast.......  You are asking for information overload.  If you know exactly
> what you want it may be easier for us (in this list) to help guide you to
> the best option.
>
> I also was once curious and found the link below.  The end of the paper has
> charts comparing different features.
> http://apps1.eere.energy.gov/buildings/tools_directory/pdfs/contrasting_
> the_c
> apabilities_of_building_energy_performance_simulation_programs_v1.0.pdf
>
> Another sight.
> http://www.wbdg.org/resources/energyanalysis.php
>
>
> I use Trace 700 (v6.2.4).  Why? Because the first, second and third company
> I worked for used it.  It is good for running loads, but so-so for energy
> modeling.  Also I have never used anything else.  I have looked at equest
> and DOE, they both look like learning a completely new programming
> language.
>
>
> I wouldn't mind hearing other people's brief views of the programs they
> use.
> Equest, DOE, HAP, ect.
>
>
>
> John Eurek LEED AP
> Mechanical Engineer,
> US Army Corps of Engineers
> Omaha District CENWO-ED-DA
> 1616 Capitol Avenue
> Omaha, NE 68102
> Phone: (402) 995-2134
> email: john.s.eurek at usace.army.mil
>
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Peterson,
> John
> (EYP/HP CFS)
> Sent: Wednesday, March 17, 2010 2:03 PM
> To: bldg-sim at lists.onebuilding.org
> Subject: [Bldg-sim] Discrepancy between Equest & Trace 6.2
>
>
>
> Has there been any information released on the differences between
> energy
> simulation programs?  We have a bid requirement with a certain
> percentage
> listed and we have been asked to address the differences between the bid
> model and the newly proposed model.
>
>
>
> Thanks in advance -
>
> John
>
>
>
> John Peterson, PE, LEED AP
>
> HP Critical Facilities Services delivered by EYP
>
> 6600 Rockledge Drive, 4th Floor
>
> Bethesda, MD  20817
>
> cell: 202-731-5835
>
>
>
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