[Equest-users] Unexpected Custom SHGC Results

[Chris Jones]

I firmly believe that interfaces that do the work for you end up 
crippling your understanding of the underlying program if you don't 
pay attention.

My first modelling assignment:
I was given a copy of the DOE2.1e Basics, a clipboard, rolling ruler 
and tape measure.  I was sent to an existing building and was 
instructed to find as much design documentation as was available and 
measure the rest.  I found some floor plans and elevations and the 
monthly utility bills.

 From that I was to construct the DOE2 model using a text editor and 
the command line to run the model.

I constructed the model using full X,Y,Z and calibrated to the utility bills.

With that approach, I was forced to RTFM, something that seems to 
escape most novices.

Unfortunately, that has left me with a good understanding of the 
underlying engine but I am terribly slow at constructing models via 
the interface.  I am much more comfortable using DOE22 directly.  I 
just update the USRLIB.dat file to contain the eQ_lib.dat 
information.  The results are the same but the models run faster.



At 06:30 PM 15/07/2012, Joe Huang wrote:
>I totally agree. The suggestion that eQUEST is flawed in modeling 
>such a basic heat transfer process as solar gain through windows is 
>extremely unlikely. My experiences in doing such parametrics with 
>DOE-2 over many years if not decades is not that the program  is 
>wrong, but that it's considering many other factors often overlooked 
>in a simplistic view of things. Chief among these are the sizing of 
>the HVAC system, its configuration, and operations. At the bare 
>minimum, you should make sure that you input the same system size in 
>both runs. Furthermore, in a mild climate like San Jose, something 
>as innocuous sounding as COOL-CONTROL=WARMEST can cause havoc in the 
>expected savings. In all the runs I've looked at, there was always 
>an explanation when the results  do not meet or run counter to the 
>original expectations. In fact, I regard those as the most valuable 
>instances for using building energy simulations.  After all, if all 
>you want is confirmation of your back-of-the-envelope estimates, why 
>do a simulation at all? Just do a degree-day calculation instead.
>
>Sent from my iPhone
>Joe Huang
>White Box Technologies
>346 Rheem Blvd Suite 108D
>Moraga CA 94556
>(o) 1(925)388-0265
>(c) 1(510)928-2683
>yjhuang at whiteboxtechnologies.com
>
>On Jul 15, 2012, at 5:53 PM, Chris Jones <cj at enersave.ca> wrote:
>
> > I can think of a number of reasons why you might see an increase 
> in cooling and fan "load".  Without spending some time looking at 
> the input/output, it is pretty hard for me to offer any definite 
> opinion.  I know for myself, it is generally an input assumption I 
> hadn't considered, not a flaw on the modelling program.
> >
> > For doing analysis on an existing building, you want to make sure 
> your inputs are not defaulting and that the model somewhat matches 
> the building.
> >
> >
> >


Chris Jones, P.Eng.
14 Oneida Avenue
Toronto, ON M5J2E3
Tel. 416 203-7465
Fax. 416 946-1005