[Bldg-sim] eQuest: Slab on Grade Ueff Calculation (UndergroundWall)

[Michael Tillou]

Neal and Brett,
 
>From my own experience trying to figure out what eQuest is doing I can
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,
 
mike
 
Michael Tillou, PE, LEED
Tillou Engineering, LLC
Williamstown, MA 01267
P: 413-458-9870 C: 413-652-1087

  _____  

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Kruis, Neal
Sent: Thursday, March 27, 2008 11:55 AM
To: Brett Fero; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] eQuest: Slab on Grade Ueff Calculation
(UndergroundWall)



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

Center for Buildings and Thermal Systems

National Renewable Energy Laboratory

1617 Cole Blvd.

Golden, CO 80401

(303) 384-7591

  _____  

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Brett Fero
Sent: Tuesday, March 25, 2008 9:24 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] eQuest: Slab on Grade Ueff Calculation (Underground
Wall)

 

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

RobsonWoese, Inc.

5824 Widewaters Parkway

East Syracuse, NY 13057

 

 

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