# Modeling Heat Transfer Between Conditioned and Unconditioned Spaces

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Dear All,

I encounter the following situation in many of the projects I work on, but
do not know how to represent best in Trace:

I have a conditioned room with a thermostat setpoint of 75 for cooling.
While some of this room's walls might be exterior, the room is also adjacent
to many unconditioned spaces. These unconditioned spaces have walls to the
exterior.

I tried to understand how Trace calculated heat transfers across walls and
partitions by using an extreme and simple example and analyse the results:

Rooms:
1 - Core Room - Design Cooling dry bulb = 75, Internal Loads is People with
the Library Template, available 100%
2 - Perimeter Room - Design Cooling dry bulb = 150 F
*0 Plenum Height for both rooms

Walls:
1 - Perimeter Room has 800 sqf walls distributed evenly among N, S, W and E
orientations.

Partitions:
2 - Core Room has 200 sqf partitions with Method: Adjacent Room to Perimeter
Room

Systems:
Core Room System - Variable Refrigerant Volume assigned to 2 - Core Room
with every setting unchanged
Perimeter Room System - Variable Refrigerant Volume assigned to 1 -
Perimeter Room with every setting unchanged
(I think I should have been okay just making one system for both rooms, as I
can choose to have thermostats and coils separately in each room, but I am
trying as best as I can to make Trace do what I want and hoped this would
help)

Plants:
Air Cooled Unitary - VRF Cooling Only assigned to systems above with every
setting unchanged

Climate:
Calcutta, India (VERY HOT)

Now, I calculate the results and I view the Building Temperature report in
the Analysis Report tab. For the core room, the report states that there are
0 hours of unmet cooling load. Moreover, the maximum temperature reached in
this room is 94 F and the most common temperature range for the Core Room is
85-90 F, all temperatures far above the setpoint of 75. I am wondering why
there are no unmet cooling load hours when the setpoint temperature for the
Core Room is hardly achieved?

I chose to put a system in the unconditioned Perimeter Room, because without
a system it seemed like Trace would not keep track of the temperature of
this space. I ended up with 0 cooling load for the Core Room when omitting a
system for the perimeter room. However, by setting the setpoint of the
Perimeter Room to the maximum of 150, I can place a system in this space
that should hardly ever operate.

I would appreciate any advice you can provide on this modeling scenario in
Trace.

I am running Trace 700, version 6.1.3.

Sincerely yours,

*Ulrik Welle-Strand Horn *

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