eQuest: Slab on Grade Ueff Calculation (Underground Wall)

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I am modeling a slab-on-grade floor using the methods described under the
help for the U-EFF. This is the described in the Volume 3: Topics/ Envelope
Components / Underground Wall eQuest 3.61e help files. A sample calculation
is presented for the 100 ft x 50 ft slab-on-grade floor. The sample input
is given as follows;

LAY-SLAB-1 = LAYERS
MATERIAL = ("Soil 12in","Conc HW 140lb 4in (CC03)")
INSIDE-FILM-RES = 0.77 ..

CON-SLAB-1 = CONSTRUCTION
TYPE = LAYERS
LAYERS = LAY-SLAB-1 ..

SLAB-1 = UNDERGROUND-FLOOR
HEIGHT = 50
WIDTH = 100
TILT = 180
PERIM-EXPOSED = 300
PERIM-CONDCUT = 0.50
CONSTRUCTION = CON-SLAB-1 ..

eQuest 3.61e does not appear to accept the PERIM-CONDUCT and PERIM-EXPOSED
keywords as input. Instead it uses the keyword U-EFF.

In Vol 23, No.6 of the Building Energy Simulation User News for DOE2.1E,
slab-on-grade calculations were presented using the following;

Reff = A/(F2 x Pexp) where Reff = Reffective, A = area of slab (ft), F2 =
perimeter conduction factor, and Pexp = exposed perimeter length (ft).

So, is U-EFF required in eQuest 3.61e calculated as U-EFF = 1/Reff = (F2 x
Pexp)/Area using F2 factors from Table 9?

Or, is there a way that I should be entering PERIM-EXPOSED and PERIM-CONDUCT
for each floor?

Thanks in advance for any help clearing this up for me.

Brett Fero, P.E., LEED AP

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Brett,

My understanding is that the PERIM-CONDUCT and PERIM-EXPOSED keywords
are not yet implemented in the DOE-2.2 engine (used by eQuest). The
U-EFFECTIVE keyword, taken from the DOE-2.1E engine, is no longer used
in DOE-2.2 (but for some reason the program doesn't complain when you
try to use it - instead it just ignores any input for this keyword).
This doesn't seem to leave much for us to work with. *Does anybody know
if eQuest does something other than specifying the U-EFFECTIVE keyword
when it asks for a U-eff input for underground surfaces?

The concept for all of these keywords comes from a paper released by
Fred Winkelmann in Building Simulation User News Vol. 23, No. 6
(http://gundog.lbl.gov/dirun/23n_d_1.pdf). The article suggests creating
a fictitious resistance layer in the wall to create the correct overall
U-value for the foundation configuration. Using the U-EFFECTIVE keyword
in addition to specifying this fictitious layer seems redundant, and you
should be able to get the same results without specifying it.

My suggestion would be to specify the fictitious layer in detailed edit
mode. That is of course if eQuest isn't already doing something behind
the scenes to calculate this layer.

Neal Kruis

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Neal and Brett,

report that the eQuest wizard correctly creates the fictitious resistance
layer using the method described in the referenced article by Fred
Winkelmann. The wizard has a fairly extensive list of insulation choices to
choose from so I recommend creating your underground wall constructions from
within the wizard thus saving you the headache of manually calculating the
properties of the required resistance layer for each underground
wall/construction type.

I often create a simple wizard project for the express purpose of building a
wall construction using the wizard defaults that I then copy and paste from
one input file into another.

yours truly,

Michael Tillou, PE, LEED

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Dear all,

I have a question for you about e-Quest. I have a typical floor in a high
rise that I'm trying to simulate according to ASHRAE 90.1 Appendix G for
LEED EAc1. The floor area is about 1200 m2 or 12916 ft2 the system applied
in the design case is Fan Coil units for the different zones + DOAU for the
fresh air. The system applied in the baseline case is system 7 (VAV with
reheat).

My question is how long do you think it will take for someone without very
much experience with e-Quest but with some simulation experience with other
tools to run the simulation with e-Quest. Thank you very much and hope to
hear from you soon.

Best regards,

Anis Ben Ayed, LEEDR AP

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Joined: 2011-10-02
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