The objective of the first part of this report, is to analyze the cooling load demands of the Wawa
store #8053 located in Philadelphia. The RTSM spreadsheets were used to analyze cooling loads when
the store is completely empty of internal loads: no equipment, occupant or lighting loads. The building
characteristics of the Wawa drawings were used to complete the spreadsheet for the wall composition.
The building was broken into three zones, the refrigeration room, Z1, the food preparation area, Z2, and
the retail area, Z3.
The ACH decided for each zone were determined by taking occupancy loads, equipment loads,
and lighting loads into account. The refrigeration room will only have someone in it when supplies are
being loaded into the space, other than that, it will remain unoccupied. Based on this, it was assumed to
have an ACH of 2 to provide minimum ventilation air for the space. The retail area is the most populated
zone throughout the day. However, the equipment loads are not high for this area, so the space was
designed for 6 ACH. The food preparation zone has a few cooks working at a time, however, the
equipment give off the most latent and sensible heat in the zone. The model has a design ACH of 15 in
order to remove the fumes and latent heat coming off of the equipment. The design ACH for the zone is
the highest because of the amount of exhaust air removed from the space. Even though the model is
designed for zero internal loads, the air changes were designed in the case that the building was
occupied.
The building orientation starts off with the entrance of Wawa facing south. The peak cooling
loads for each zone and rotation are listed below. The peak cooling loads occur during December and
July, during the afternoon around 2pm to 6pm.
Z1 - 0°
Z2 - 0°
Z3 - 0°
Z1 - 90°
Z2 - 90°
Z3 - 90°
Z1 - 180°
Z2 - 180°
Z3 - 180°
Peak Cooling Load
Month
Hour
7
16
12
16
12
14
7
16
12
16
7
18
7
16
12
16
12
14
The cooling loads for each zone are broken down by heat gain component. The largest heat gain
was from the refrigeration room by infiltration latent heat. The refrigeration room was designed with a
metal room in the RSTM spreadsheet which may be the reason why the results are skewed. The retail
zone is the only space that has a solar cooling load because the zone’s exterior wall is mainly the glass
façade of the south entrance.
Component Cooling
Wall/Window
Roof
Solar
Z1 - 0°
635.09
0.00
0.00
Z2 - 0°
-98.63
-143.95
0.00
Z3 - 0° -3967.60
-505.21
3655.37
Z1 - 90°
676.67
0.00
0.00
Z2 - 90°
-98.63
-143.95
0.00
Z3 - 90° 10956.79
2328.02 17799.29
Z1 - 180°
870.69
0.00
0.00
Z2 - 180°
-98.63
-143.95
0.00
Z3 - 180° -3967.60
-505.21
3655.37
Loads
Inf. Sens. Inf. Lat.
18676.87 25658.22
-901.33
-31.89
-542.41
-17.10
18676.87 25658.22
-901.33
-31.89
715.60
1063.68
18676.87 25658.22
-901.33
-31.89
-542.41
-17.10
BTU/hr
Total Cooling Load
50000
45000
40000
35000
30000
25000
20000
15000
10000
5000
0
Z1 - 0°
Z2 - 0°
Z3 - 0°
Z1 - 90°
Z2 - 90°
Z3 - 90°
Z1 - 180°
Z2 - 180°
Z3 - 180°
Zone - Rotation
Since the refrigeration room is a metal box, the roof was modeled as a metal interior surface
because the space above is empty. Therefore the infiltration load dominates in this zone. The kitchen is
mainly an interior room, so it is separated from the exterior conditions. Therefore, the kitchen does not
require as big of a cooling load because it is protected by interior spaces. The infiltration dominates the
kitchen zone. The retail area zone is dominated by the solar heat gain because of the fenestration on the
south façade.
After the first analysis, the building was rotated 90 degrees then 180 degrees, so the glass
entrance is now facing north. The main changes in cooling loads were due to the solar heat gains in the
retail area. Other than zone 3, the other zones had a consistent total cooling loads for all three
rotations.
The Wawa store was analyzed with internal loads by changing the equipment, lighting, and
occupant schedules. The following chart is the assumed schedule of the building for each internal heat
gain component.
Hours
People
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
The assumed ACHs for each zone are the same from the first analysis and can be found at the
beginning of this report. The peak cooling loads for the building when it is occupied occur during the
summer in the late afternoon.
Z1 - 0°
Z2 - 0°
Z3 - 0°
Z1 - 90°
Z2 - 90°
Z3 - 90°
Z1 - 180°
Z2 - 180°
Z3 - 180°
Peak Cooling Load
Month
Hour
7
16
7
16
7
18
7
16
7
16
7
18
7
16
7
16
7
16
In the refrigeration room, the infiltration load dominates the overall cooling load because there
aren’t people occupying the room and there isn’t a significant amount of equipment in the room. The
kitchen zone is dominated by the equipment load. The equipment load adds both sensible and latent
heat to the space, so both cooling loads equally dominate the other component heat gains. The
occupancy loads dominate in the retail area because there are always customers in the retail area, and
the equipment loads are not as high. Overall between the three zones, the occupancy load in the retail
area dominates over the other loads.
The cooling loads are significantly different for the second analysis because since the building is
occupied and there are more internal heat gains, the main cooling loads occur during July no matter the
orientation of the building. The building still has similar heat gains due to the envelope, however, the
equipment and occupant loads are more significant than the envelope loads, especially in the retail
zone, where it is heavily occupied, and the food preparation zone where there are more equipment.
At lower outdoor temperatures, the energy usage barely increases in commercial buildings.
Since the building is open 24/7, there are always customers, and the kitchen is nearly always in
operation besides during the night. The kitchen equipment produces a lot of heat and the occupants
give off a lot of latent and sensible heat. The internal components of the building are always producing
heat, so the building is nearly always in cooling mode.
Z1 - 0°
Z2 - 0°
Z3 - 0°
Z1 - 90°
Z2 - 90°
Z3 - 90°
Z1 - 180°
Z2 - 180°
Z3 - 180°
Wall/Window
635.09
311.87
10987.30
676.67
417.73
10956.79
870.69
528.22
12079.93
Roof
0.00
585.33
2328.02
0.00
585.33
2328.02
0.00
585.33
2530.75
Component Cooling Loads
Inf. Sens. Inf. Lat. People Sens. Equip. Sens.
18676.87 25658.22
2992.76
3530.70
1443.69
1983.33
716.59
16974.48
715.60
1063.68
23015.86
4810.91
18676.87 25658.22
2992.76
3530.70
1443.69
1983.33
716.59
16974.48
715.60
1063.68
23015.86
4810.91
18676.87 25658.22
2992.76
3530.70
1443.69
1983.33
716.59
16974.48
774.26
1063.68
22881.30
4807.16
Solar
0.00
0.00
10561.67
0.00
0.00
17799.29
0.00
0.00
6255.92
People Lat. Equip. Lat.
2400.00
0.00
581.00
10423.14
18686.67
0.00
2400.00
0.00
581.00
10423.14
18686.67
0.00
2400.00
0.00
581.00
10423.14
18686.67
0.00
Total Cooling Loads
(Internal Loads Included)
90000
80000
70000
BTU/hr
60000
50000
40000
30000
20000
10000
0
Z1 - 0°
Z2 - 0°
Z3 - 0°
Z1 - 90°
Z2 - 90°
Z3 - 90°
Zone - Rotation
Z1 - 180°
Z2 - 180°
Z3 - 180°