[Equest-users] Modeling inefficiencies of existing buildings

[R B]

My first reaction is that you would need other tools that are more flexible
in allowing for system descriptions. Following are some suggestions (which I
have not tried) so I would be interested in knowing how you finally end up
modelling these in eQuest.

Q1 - You could calculate the amount of reheat energy at 30% that goes into
each zone and input that as an internal source energy, with a schedule. I
think this will work but maybe it has some repercussions that I have not
thought about. Another option could be that you set the min flows to 0.3 on
the air side as well as the hot water loop (not sure if this will work).

Q2 - See if setting the lighting type to REC-FLOUR-RSV and changing the
light-to-space, and light to-return makes any difference.

SUS-FLUOR                 Suspended, surface mounted or recessed/non-vented
fluorescent or HID.

REC-FLUOR-NV            Recessed fluorescent or HID not vented to return air
or supply air.

REC-FLUOR-RV            Recessed fluorescent or HID vented to return air.

REC-FLUOR-RSV          Recessed fluorescent or HID vented to supply and
return air.

INCAND                      Incandescent or tungsten-halogen.
Q3 - Not sure what you could do here other than use the duct losses input
tabs in eQuest. There is a paper by LBNL folks - Duct Leakage Modeling in
EnergyPlus and Analysis of Energy Savings from Implementing SAV with
InCITeTM - that could give you some idea on what increases in energy to
expect. If eQuest does not give you expected results, you might want to go
to energyPlus. FSEC has done work on duct leakage and I think also
updated/implemented it in energygauge software (based on doe-2) - you could
see if they have any papers written about modelling it.

Thanks and good luck
-Rohini


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Rohini Brahme, Ph.D. LEED AP
Building energy analysis, tool development, and training
Dallas/Fort Worth, TX

On Mon, Nov 8, 2010 at 7:36 PM, John Bixler <JBixler at sebesta.com> wrote:

>  Hello all,
>
>
>
> I’ve been using eQuest recently to support studies of existing buildings,
> and to evaluate the energy savings of different options.
>
>
>
> I’ve struggled with trying to model some of the problems we’ve discovered
> in the older buildings.  Any thoughts on the following would be greatly
> appreciated.
>
>
>
> 1.       Failed reheat valves:  Reheat valves that are stuck in the open
> position.  Not only does this increase the heating hot water use, but it
> should affect fan energy and chilled water use as well.
>
> 2.       Light troffer diffusers:  All the vogue in the 60s and 70s, these
> combination lights and diffusers result in a large thermal gain as the air
> enters the zone.  eQuest has “duct delta T”, however that assumes a heat
> loss under cooling.  This condition is always a gain of heat (and
> technically this will vary based on the temperature of the air entering the
> zone).
>
> 3.       Duct Leakage:  A massive problem until recently, measured leakage
> values can often be 30% or more.  eQuest has an apparent entry for this,
> however, each time I’ve enabled it, I’ve seen large REDUCTIONS in energy
> use.  Again, this is a condition that results in increased usage of all
> utilities as the zones struggle to meet their setpoints.
>
>
>
> Also, duct leakage is assigned at the system level.  It appears eQuest then
> wants you to assign what plenum the duct is leaking “to”.  Depending on how
> I specified my systems in the wizard, I have ended up with a plenum zone for
> each zone on a floor (which might mean 30 zones per floor) or one big plenum
> per floor.  If I have a system that serves zones on several floors, it
> dosent seem like eQuest will let me assign the leakage to go all the plenums
> the system is assigned to, evenly.  I have to pick a SINGLE zone that all
> the leakage goes to.
>
>
>
> Thanks,
>
>
>
> *John Bixler, LEED AP BD+C*
>
> Mechanical Designer
>
> Sebesta Blomberg
> sebesta.com | P  319.364.1005 | M  319.558.9299
>
>
>
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