[Equest-users] Attic insulation

Joe Huang yjhuang at whiteboxtechnologies.com
Thu Mar 13 19:11:42 PDT 2014


Here's an attempt to answer your questions.
In DOE-2, which is the simulation engine behind eQUEST, the simulation is done in stages - 
first LOADS, and then SYSTEMS and PLANT.  LOADS calculates the heat flows at constant 
reference space temperatures.  These heat flows are passed to SYSTEMS, during which DOE-2 
calculates the actual zone temperature taking into account the heat flows, the heat input 
or extraction from the HVAC system, etc.   The ceiling is considered an internal wall, 
since it's NEXT-TO to the attic and not the outdoors. Thus, the heat flows will appear as 
through internal walls in the space report, and not all in any building report in LOADS. 
Furthermore, since the space temperatures are user-defined, the heat flow through the 
ceiling would simply be its U-value times the difference between the user-defined 
temperatures for the house and the attic.  As you've noticed the loads in LOADS is not the 
same as the loads in the SYSTEMS reports for reasons already given.  If you want the zone 
loads without any SYSTEM effects, you should specify SYSTEM-TYPE as SUM, which will simply 
hold the zones to the thermostat setpoints and calculate the heat flows under those 
conditions.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"


On 3/13/2014 5:06 PM, Charles Hoes wrote:
> Hi
>
> I seem to be a complete novice with eQuest because of how basic this question is.  I am 
> modeling a simple, one story building on a slab. The building has flat, 8' ceilings and 
> a pitched roof.  There is a sheet rock ceiling, with blown insulation on top of that, 
> then an "attic space" covered with a roof.
>
> It seems logical that the "Top Floor Ceiling (below attic)" fields would apply to the 
> ceilings.  It also seems logical that the type of insulation would apply to the blown in 
> insulation on top of the ceiling.
>
> When I run the simulation, I expect the "LS-A Space Peak Load Summary" to give me a 
> summary of the space peak loads and the building peak loads.  However, while it looks 
> like it does this, it does not include the ceilings.  It gives the same answer no matter 
> what I do with the insulation values as noted in the previous paragraph.  It is as if 
> the ceiling is totally ignored.  LS-C shows the same peak values as LS-A.
>
> I have noticed that a report called SS-D Building Load Summary also gives something that 
> looks like building peak loads, but it is a little higher than those provided in LS-A 
> and LS-C.  It does change when I change the ceiling insulation.
>
> My quandary has to do with if LS-A and LS-C do not give a summary of the space peak 
> loads, what do they represent.  I also wonder if SS-D will give what is sometimes called 
> the "district" heating loads (the loads that are required to maintain the temperature 
> set points without regard to the details of the HVAC system).
>
> Any help is understanding these reports, and why LS-A and LS-C does not reflect the 
> ceiling insulation while SS-D appears to.
>
> Thanks
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