Re: [EnergyPlus_Support] Question About Modeling Moisture

["Michael J. Witte" <mjwitte@xxxxxxxx>]

Just the exposed materials, the inside layer of material, which is the last one
in each CONSTRUCTION object.

On 19 Apr 2005, at 19:11, Charles Bartlett wrote:

>
> Michael,
>
> When you say all surfaces, do you mean all exposed surfaces (walls and floors)
> or all surfaces, even those inside the wall such as insulation.  I'll let you
> know what I find out.
>
> Thanks for your help...
>
> Chuck Bartlett
>
> "Michael J. Witte" <mjwitte@xxxxxxxx> wrote:
> The problem in this file is that moisture properties have been specified only
> for some of the surfaces in the conditioned space.  The EMPD model is supposed
> to accomodate this situation, but apparently it is not.  I added concrete
> moisture properties for the slab floor and the summer conditioned space RH (with
> Chicago weather) moves into the 40% range, peaking over 50%.  I would recommend
> that you make sure there are moisture properties defined for the inside material
> layer for all surfaces and sub-surfaces (except windows) which are present in
> the conditioned zone.  A change request will be submitted to investigate if
> partial specification of moisture properties should be allowed and if so, if the
> model is handling this properly.
>
> Mike
>
>
> On 14 Apr 2005, at 13:12, bartlettbmw wrote:
>
> >
> >
> > I am trying to model the effects of different HVAC system designs on
> > indoor humidity levels in a residential home.  Using the CTF solver,
> > the loads seem about right, but the indoor relative humidity varies
> > much more than would be expected.  Looking into the EP
> > documentation, it appears that there are two options, EPDM and MTF,
> > availible to improve the model and more accurately account for
> > moisture loads.  Since I am interested in running an annual
> > simulation, the MTF solution probably will not work because the
> > documentation warns of problems for annual simulations due to non-
> > linearities in material properties with temperature.  This leaves
> > the EPDM method.  Since the biggest moisture sink for the building
> > will probably be the drywall, I imported the Gypsum EPDM properties
> > from the included datasets.  When I run the simulation with these
> > properties the results are given relative humidity values that are
> > way too low (20% during the summer).  I tried adjusting the values
> > for other materials with much lower moisture capacity, but the
> > result is about the same.  I was wondering if anyone has used the
> > EPDM model to achieve a resonable approximation to internal moisture
> > loads, or if there is another way to model the loads that would be
> > more accurate.
> >
> >
> >
> >
> >
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> >
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> >
> > Attachments are not allowed -- please post any files to the appropriate folder
> > in the Files area of the Support Web Site.
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
>
>
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support
> EnergyPlus-Support@xxxxxxxx
>
>
>
>
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>
> The primary EnergyPlus web site is found at:
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>
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> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
>
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