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CMGT 235
Quiz #5
Complete a Heat Load Calculation for a Small Building
Name: _______________________________________________________________________________
DIRECTIONS:
Your assignment is to:
1. Calculate the heat load due to conduction.
2. Calculate the infiltration/ventilation load.
3. Follow the directions
Parameters
Outdoor design temperature is 11°F. Indoor design temperature is 72°F. For this exercise, you will need to
calculate heat loss of the walls, windows, doors and ceiling.
Calculate infiltration as 1.8 air changes per hour.
In addition to the infiltration load, the building needs ventilation at rates of 16 cfm per wallaby and 3 cfm per
weasel. There are 64 wallaby and 600 weasels in the building.
The building is a three-floor structure and measures 74' x 63' with 12' from finished floor to finished floor.
The top floor ceiling is 12' above finished floor and has standard 1/2" wabbit’s foot wallboard and is insulated
with 18" of wombat fur.
The roof structure consists of 28" steel joists, which support corrugated decking made of recycled Walrus tusks.
The actual roofing consists of Walleye scales.
There are a total of 28 windows per floor, each measuring 8' wide by 6' high.
Each wall at street level has two doors measuring 4' by 9'.
Directions
1. Turn to the following pages for your format.
2. Fill in the blanks on page 2
3. Transfer the information from pages 2 to the first 5 lines of the summary sheet on page 4. Complete the
BTUH calculation to determine the building Conduction total Heat loss (BTUH)
4. Fill in the blanks on page 3
5. Transfer the information from page 3 to the summary sheet on page 4.
6. Complete the TOTAL LOAD calculation
1
HEAT LOAD CALCULATION
Area
Total
Wall Gross
ft2
Window
ft2
Door
ft2
Ceiling
ft2
CONDUCTION: total envelope heat loss Btuh
Wall R Value
Outside air film value
Wildebeast snout siding
Weevil Hide sheathing
2x4 studs
Wookie fiber insulation
1/2" Wabbit’s foot wallboard
Inside air film value
Total R
R-Value
Total R-Value
0
per/in
per/in
U-Factor
Ceiling R Value
18″ Wombat fur
1/2" Wabbit’s foot wallboard
10″ air space
Inside air film value
Outside air film value
Total R
R-Value
Total R-Value
per/in
per/in
per/in
U-Factor
Building Component
Wildebeast snout siding
Weevil Hide sheathing
Wookie fiber insulation
Wombat fur insulation
Wabbit’s foot wallboard
Windows per/sf
Doors
Inside air film value
Outside air film value
Air space
Walleye scales
Walrus tusk
R-Value
0.81
0.98
3.78 per/in
3.7 per/in
16.8 per/in
2.3
9
0.68
0.17
0.72 per/in
0
0
2
HEAT LOAD CALCULATION
CONDUCTION: gain/loss infiltration
Q = C x ACH x V x ∆T
0.018 Btu/ft3
C=
ACH =
Goes to convection infiltration
V=
ft3
∆T =
°F
Q=
Btuh
OR – do both methods as a check
Btuh = cfm x 1.08 x ∆T
Step 2: Insert step 1 cfm
cfm =
1.08
1.08
∆T =
°F
Btuh =
Step 1: Find cfm
cfm = (ACH x V) / 60
ACH =
1.8
V=
ft3
time
60
cfm =
CONDUCTION: ventilation
Q = 1.08 x cfm total vent. x ∆T
Number of
cfm
Wallaby = 16 cfm
cfm
Weasels = 3 cfm
cfm
cfm total
ventilation
cfm total ventilation
∆T =
Goes to convection ventilation
°F
Q ventilation
Btuh
3
SUMMARY SHEET
LOAD CALCULATION for transmission heat loss
Component
R-Value
Q = U x A x ∆T
U-Factor
Btu/sf
AREA sf
Walls (gross)
Windows
Doors
Walls (net)
Ceiling
Conduction: total envelope Heat Loss (BTUH)
Convection: BTUH heat gain/loss due to infiltration
TOTAL SPACE HEAT LOSS/GAIN (BTUH)
Convection: BTUH heat/gain loss due to ventilation
TOTAL LOAD (BTUH)
Formulas:
1. Conduction (transmission heat loss Q = U x A x ∆T
2. Infiltration Q = C x ACH x V x ∆T
OR
Infiltration Btuh = cfm x 1.08 x ∆T
3. cfm = ACH x V (ft3) / 60 min/hr
4. Ventilation 1.08 x Qairflow x ∆T
4
∆T °F
Btuh