Attic insulation

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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

ChasHoes's picture
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Joined: 2014-01-09
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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.
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Moraga CA 94556
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Joe Huang's picture
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