# Re: [EnergyPlus_Support] Slab Programme

```Answers regarding questions about inputs to the slab program
(\EnergyPlus\PreProcess\GrndTempCalc\slab.exe):

> Surface Albedo: NO Snow/Snow?

This will change the ground surface temperature by reflecting solar
energy.  The Albedo is more commonly recorded than the absorptivity.
The albedo can range from as low as 0.05 for blacktop surfaces to
0.95 for fresh snow.  Representative average values for North America
are 0.16 in the summer and 0.40 in the winter.   Ref:  Sellers,
Physical Climatology, Univ of Chicago Press, 1965( from W. P.
Bahnfleth, Ph.D. Thesis, University of Illinois, Mech Eng Dept,
Urbana, IL, 1989)

> Under slab insulation: What does such a insulation look like as
> the next field in the object depicts the width of strip of
> insulation.

This is a layer of horizontal insulation of the width and thermal
resistance specified underneath the slab all around the perimeter.

> The area to perimeter ratio for this slab: this term is
> self-explaining, but in the example idf-File
> (Slab2x2VertInsMplsAP10) this ratio is 10- the specified dimension
> of this slab is 12x12.

The example uses the EquivSlab and EquivAutoGrid options.  Thus the
input in the AutoGrid object is not used.  The A/P ratio of 10 is
used.

> Thickness of slab on grade?

This specifies the floor slab thickness.  It is used in conjunction
with the "Slab k" field to determine the thermal resistance of the
slab.  This and the specified temperatures and heat transfer
coefficients can be used to estimate the monthly heat flux through
the slab.

> Distance from edge of slab to domain edge?

This value is what is used to set up the grid for the
multidimensional calculation.  It should be far enough from the slab
to be in an undisturbed ground temperature.   15 meters is quite
reasonable.

On 4 Oct 2002, at 13:32, alexander.beisteiner@fh-pinka wrote:

> Using the programme Slab for calculating the ground temperature I
> would need some help creating the IDF. Some fields in the various
> objects are unclear to me:
>
> Surface Albedo: NO Snow/Snow?
>
> Under slab insulation: What does such a insulation look like as the
> next field in the object depicts the width of strip of insulation.
>
> The area to perimeter ratio for this slab: this term is
> self-explaining, but in the example idf-File (Slab2x2VertInsMplsAP10)
> this ratio is 10- the specified dimension of this slab is 12x12.
>
> Thickness of slab on grade?
>
> Distance from edge of slab to domain edge?
>
> I am looking forward to your help.
> Kind Regards
>
>
> ----------------------------------------------
> Alexander Beisteiner
> Forschungs- und Technologietransfer
> Pinkafeld GmbH
> Steinamangerstrasse 21
> 7423 Pinkafeld
>
> Tel.: 0043/3357/45370-1324
> alexander.beisteiner@xxxxxxxxxxxxxxxxxx
> http://www.fh-pinkafeld.ac.at
>

========================================================
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx

http://us.click.yahoo.com/pt6YBB/NXiEAA/jd3IAA/dkFolB/TM
---------------------------------------------------------------------~->

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

The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

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

```