Re: [EnergyPlus_Support] Ground temp problems

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

Sorry to hear this has been frustrating your modeling.  Nobody has identified 
this as a problem before now.  We will review the current approach vs your 
suggestion.  If you have inputs (slab, basement, and EnergyPlus) that you would 
be willing to share which illustrate the problem, please zip and send to me at 
energyplus-support@xxxxxxxx 

One thought that comes to mind is that Slab and Basement report heat flux 
values as well as outside face temperatures.  Given the flux value and the slab 
surface temperature, you could compute the temperature of the outside face of 
the insulation, and then model the slab+insulation in EnergyPlus.  

Mike

On 14 Nov 2007 at 21:38, taharvey2001 wrote:

> We keep finding the ground loss methods in E+ nearly unusable. The fact that the
> Slab preprocessor generates a fixed floor temperature at the outside surface of
> the slab, instead of the outside surface of the insulation causes all sorts of
> havoc with the rest of the dynamic simulation. We always end up with bogus
> building results from using slab.exe. With well insulated slabs we'll  see
> nonsense like the slab heating the space with a large positive energy balance
> during night setbacks because the static temperature it on the wrong side of the
> insulation.
> 
> It would be much more useful (and accurate) if the slab & basement preprocessors
> would generate ground temperatures on the *outside* surface of the *whole* floor
> assembly (or basement wall), then you would model the wall or floor construction
> assembly as normal in E+. That would allow the slab or wall surface temperature
> to float, and react realistically to internal conditions and solar radiation.
> Also with the current preprocessor configuration the preprocessor doesn't handle
> multi-layer basement wall assemblies (ICFs, etc).
> 
> I'd like to hear any workarounds til this gets fixed.
> 
> Currently we have been adding 6' of soil in a few layers below the slab, and
> running a undisturbed soil temperature program, to generate monthly soil temps
> for a depth equal to the average vert. depth + horz. length. Of course this
> doesn't consider the building influence on ground temperatures. At high levels
> of ground insulation it appears to get reasonable results, though at low or no
> insulation I have my concerns. 
> 
> 
> 
> 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.
> 
> EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the
> Documentation link and press the "search" button.
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 


========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx





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.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/join
    (Yahoo! ID required)

<*> To change settings via email:
    mailto:EnergyPlus_Support-digest@xxxxxxxxxxxxxxx 
    mailto:EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx

<*> To unsubscribe from this group, send an email to:
    EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/