HEAT LOAD COMPUTATION SHEET

Project: PUP – MAIN (South Wing)

Room #: RM 501 – CMIT Laboratory Room
Name of Area: 5th Floor
Sheet No.: 1/18
Prepared by: VALENCIA, Guillermo T.

I. External Heat Loads

ROOF
Qroof = UroofAroofCLTDroof
Since there is no roof on 5th Floor,
Qroof = 0

WALLS
𝐵𝑇𝑈
Q = U x A x CLTD; U = 0.263 ℎ𝑟−𝑓𝑡 2 −°𝐹 (From Table 6.3 in 1989 ASHRAE Handbook: Group F)

CLTDC = {(CLTDm + LM) (K) + (Tc – Tr) + (Tm – Ta)}

Where: CLTDC = Corrected Cooling Load Temperature Difference
CLTDm = Maximum Cooling Load Temperature Difference
LM = Latitude per Month
K = Correction Factor for Color of Surface
Tc = Human Comfort Body Temperature
Tr = Actual Room Temperature
Tm = Average Mean Temperature
Ta = Room Temperature Design

Anorth wall = Awall – Awindows From Table 6.2 ASHRAE Handbook Group F
Walls @1400 Hr. (Peak time 2 P.M)
Anorth wall = (29.68 ft. x 8.53 ft.) – (88.89 ft.2) CLTDm (north) = 17°F – North Exposure
Anorth wall = 164.28 ft.2 CLTDm (south) = 32°F – South Exposure
Asouth wall = Awall – Awindows – Adoors From Table 6.4 ASHRAE Manual, October
Design, Latitude/Month
Asouth wall = (29.68 ft. x 8.53 ft.) – (57.78 ft.2) – LM = -3 North
(44.42 ft.2) = 150.97 ft.2 LM = +7 South
Color Factor (K) = 0.83 (Rural Medium Color)

CLTDC (north) = {(17°F – 3) (0.83) + (78°F – 77°F) + (81°F – 85°F)} = 8.62°F (North Wall)
CLTDC (south) = {(32°F + 7) (0.83) + (78°F – 77°F) + (81°F – 85°F)} = 29.37°F (South Wall)

𝐵𝑇𝑈
Qnorth wall = U x A x CLTDC (north) = (0.263 ℎ𝑟−𝑓𝑡 2 −°𝐹) (164.28𝑓𝑡 2 )(8.62°F) = 372.43 BTUH
𝐵𝑇𝑈
Qsouth wall = U x A x CLTDC (south) = (0.263 ℎ𝑟−𝑓𝑡 2 −°𝐹) (150.97𝑓𝑡 2 )(29.37°F) = 1166.14 BTUH
Qt Walls = 1538.57 BTUH

GLASS CONDUCTION
𝐵𝑇𝑈 From Table A.8 - 1997 ASHRAE Handbook
Q = U x A x CLTD; U = 1.01 ℎ𝑟−𝑓𝑡 2 −°𝐹

CLTDC = 13°F From Table 6.5 1993 ASHRAE Handbook

@1400 Hr. (Peak time 2 P.M)
CLTDC = 13°F + 3°F = 16°F From Table 10 1993 ASHRAE Handbook Rule
(a) For Glass

Awindows (north) = 88.89 ft.2

Awindows (south) = 57.78 ft.2

Q = U x A x CLTD
𝐵𝑇𝑈
Qnorth = (1.01 ℎ𝑟−𝑓𝑡 2 −°𝐹) (88.89𝑓𝑡 2 )(16°𝐹) = 1436.46 BTUH
𝐵𝑇𝑈
Qsouth = (1.01 ℎ𝑟−𝑓𝑡 2 −°𝐹) (57.78𝑓𝑡 2 )(16°𝐹) = 933.72 BTUH
Qt Glass Conduction = 2370.18 BTUH
SOLAR HEAT GAIN
Q = A x SC x SHGF x CLF
Where: A = Area of glass
SC = Shading Coefficient
SHGF = Solar Heat Gain Factor
CLF = Cooling Load Factor

Awindows (north) = 88.89 ft.2

Awindows (south) = 57.78 ft.2

SC = 0.81 From Table 6.7 1993 ASHRAE Handbook, for

Single clear glass with dark interior
shading

𝐵𝑇𝑈
SHGFnorth = 33.28 From Table 15, at 16° Latitude/October
ℎ𝑟−𝑓𝑡 2
𝐵𝑇𝑈 1997 ASHRAE Handbook
SHGFsouth = 150.26 ℎ𝑟−𝑓𝑡 2

CLFnorth = 0.86 From Table 6.10, at 2 P.M. for Glass

CLFsouth = 0.68 with Interior Shading (All Room
Constructions) 1989 ASHRAE Handbook

Q = A x SC x SHGF x CLF

𝐵𝑇𝑈
Qnorth = (88.89 𝑓𝑡.2 )(0.81) (33.28 ℎ𝑟−𝑓𝑡 2 ) (0.86 ) = 2060.72 BTUH
𝐵𝑇𝑈
Qsouth = (57.78 𝑓𝑡.2 )(0.81) (150.26 ℎ𝑟−𝑓𝑡 2 ) (0.68 ) = 4782.06 BTUH
Qt Solar Heat Gain = 6842.78 BTUH

CEILING
Qceiling = U x A x TD
Since there is no roof/ceiling on 5th Floor,
Qceiling = 0

PARTITIONS
𝐵𝑇𝑈
Qwest partition = U x A x TD; U = 0.263 ℎ𝑟−𝑓𝑡 2 −°𝐹 ; TD = 3°F
(From Table 6.3 in 1989 ASHRAE Handbook: Group F)

Awest partition = 187.51 ft.2

𝐵𝑇𝑈
Q = (0.263 ℎ𝑟−𝑓𝑡 2 −°𝐹) (187.41𝑓𝑡 2 )(3°F)
Qt Partition = 147.87 BTUH

EXTERNAL TOTAL HEAT LOAD

- Summation of #’s 1-6

QTotal External = 1538.57 + 2370.18 + 6842.78 + 147.87

QTotal External = 10899.40 BTUH

II. Internal Heat Loads

A. Sensible Heat Components

LIGHTS
QS = Input x CLF
Where: Input = Watts Actual Light Load
CLF = Cooling Load Factor of Lights (Depending on how long it is turned on)

CLF = 0.93 From Table 45 Group A in 1993 ASHRAE

Handbook: CLF when lights are on for 12
hours

QS = Input x CLF **RM 501 has 4 fluorescent lights

𝐵𝑇𝑈𝐻 QS = 114.17 BTUH x 4
QS = 36 W x 0.93 x 3.41 𝑊
QS = 114.17 BTUH / Light
QS Lights = 456.67 BTUH
PEOPLE
QS = No. of People x SHG x CLF
Where: SHG =Rate of Sensible Heat Gain from Occupants
CLF = Cooling Load Factor for People
**RM 501 has approximately 40 students a day
SHG = 250 BTU/H From Table 6.13 in 1997 ASHRAE Handbook
for moderately active office work
CLF = 0.89 From Table 6.14 in 1989 ASHRAE Handbook
CLF factors for people (10 hours after
people enter)

QS = (40 𝑠𝑡𝑢𝑑𝑒𝑛𝑡𝑠)(250𝐵𝑇𝑈𝐻)(0.97)
QS People = 𝟏𝟐𝟏𝟐𝟓. 𝟎𝟎 BTUH
APPLIANCES

QS = Heat Gain x CLF

Where: Heat Gain = Rate of Sensible Heat Gain from Equipment
CLF = Cooling Load Factor for Appliances

Heat Gain for Computers = 460.64 BTUH From Table 8 in 2001 ASHRAE Handbook for
Computers with Medium Monitor
Heat Gain for Ceiling Fans = 200 BTUH

CLF for Ceiling Fans = 1 From Table 39 in 1997 ASHRAE Handbook

for Hooded Equipment (12 hours
CLF for Computers = 0.87 operation)

**RM 501 has 35 personal computers and 4 ceiling fans

QS = (35 𝑐𝑜𝑚𝑝𝑢𝑡𝑒𝑟𝑠)(460.64 𝐵𝑇𝑈𝐻)(0.87) = 14026.49 BTUH

QS = (4 𝑐𝑒𝑖𝑙𝑖𝑛𝑔 𝑓𝑎𝑛𝑠)(200 𝐵𝑇𝑈𝐻)(1) = 800 BTUH
QS Appliances = 𝟏𝟒𝟖𝟐𝟔. 𝟒𝟗 BTUH

ROOM SENSIBLE HEAT LOAD

- Summation of #'s 1-3 x (1.05)

Q1-3 = (456.67 BTUH + 12125.00 BTUH + 14826.49 BTUH) x 1.05

QS Room = 𝟐𝟖𝟕𝟕𝟖. 𝟓𝟕 BTUH

DUCT HEAT GAIN

- 8% of Room Sensible Heat Load

QS = 28778.57 BTUH x 0.08

QS Duct Heat Gain = 𝟐𝟑𝟎𝟐. 𝟐𝟗 BTUH

DUCT LEAKAGE LOSSES

- 10% of Room Sensible Heat Load

QS = 28778.57 BTUH x 0.1

QS Duct Leakage Losses = 𝟐𝟖𝟕𝟕. 𝟖𝟔 BTUH
FAN HORSEPOWER
- 3% of Room Sensible Heat Load

QS = 28778.57 BTUH x 0.03

QS Fan HP = 𝟖𝟔𝟑. 𝟑𝟔 BTUH
FAN VENTILATION
QS = (1.10) x (CFM/person) x (To – Tr)
Where: CFM/person = Ventilation Requirement Rate
To = Outside Air Temperature
Tr = Room Temperature Design

CFM/person = 17 (From Table 2 in 2015 ASHRAE Handbook:

Design Criteria for Educational
Facilities)
To = 95°F
Tr = 77°F
𝐵𝑇𝑈𝐻
QS = 1.10 𝐶𝐹𝑀− °𝐹 x (17 CFM/person) x 40 persons x (95-77) °F = 13464.00 BTUH
QS Fan Ventilation = 𝟏𝟑𝟒𝟔𝟒. 𝟎𝟎 BTUH
EFFECTIVE ROOM SENSIBLE HEAT LOAD
- Summation of #’s 4-8

QERSHL = 28778.57 + 2302.29 + 2877.86 + 863.36 + 13464.0

QERSHL = 48286.07 BTUH

B. Latent Heat Components

PEOPLE
QL = No. of People x LHG x CLF
Where: LHG =Rate of Latent Heat Gain from Occupants
CLF = Cooling Load Factor for People
**RM 501 has approximately 40 students a day
LHG = 187.67 BTU/H From Table 3 in 1997 ASHRAE Handbook for
moderately active office work
CLF = 0.89 From Table 6.14 in 1989 ASHRAE Handbook
CLF factors for people (10 hours after
people enter)

QL = (40 𝑠𝑡𝑢𝑑𝑒𝑛𝑡𝑠)(187.67 𝐵𝑇𝑈𝐻)(0.97)

QL People = 𝟕𝟐𝟖𝟏. 𝟔𝟎 BTUH

APPLIANCES

QL = Heat Gain x CLF

Where: Heat Gain = Rate of Latent Heat Gain from Equipment
CLF = Cooling Load Factor for Appliances
Latent Load = 0 if appliance under exhaust hood (See Note # 2)

QL Appliances = 0

ROOM LATENT HEAT LOAD

- Summation of #'s 1-2 x (1.05)

Q1-2 = (7281.60 BTUH) x 1.05

QL Room = 𝟕𝟔𝟒𝟓. 𝟔𝟖 BTUH

DUCT HEAT GAIN

- 10% of Room Latent Heat Load

QL = 7645.68 BTUH x 0.10

QL Duct Heat Gain = 𝟕𝟔𝟒. 𝟓𝟕 BTUH

SUPPLY DUCT LEAKAGE

- 5% of Room Sensible Heat Load

QL = 7645.68 BTUH x 0.05

QS Supply Duct Leakage = 𝟑𝟖𝟐. 𝟐𝟖 BTUH

VENTILATION

QL = (CFM/person) x ΔW x 4840 x No. of person

Where: CFM/person = Ventilation Requirement Rate
ΔW = Change in Specific Humidity = W2 – W1

CFM/person = 17
(From Table 2 in 2015 ASHRAE Handbook: Design Criteria for Educational Facilities)
𝑘𝑔𝑤𝑣
W2 = W for 92°F DB/ 81°F WB = 0.0205 𝑘𝑔𝑑𝑎
𝑘𝑔𝑤𝑣
W1 = W for 77°F DB/ 55%RH = 0.00988 𝑘𝑔𝑑𝑎
𝑘𝑔𝑤𝑣
ΔW = 0.0106 𝑘𝑔𝑑𝑎

𝑘𝑔𝑤𝑣 𝑘𝑔𝑑𝑎
QL = (17 CFM/person) x 0.0106 x 4840 x 40 students
𝑘𝑔𝑑𝑎 𝐶𝐹𝑀−𝑘𝑔𝑤𝑣

QL Ventilation = 34886.72 BTUH

EFFECTIVE ROOM LATENT HEAT LOAD
- Summation of #’s 3-6

QERLHL = 7645.68 + 764.57 + 382.28 + 34886.72

QERLHL = 43679.25 BTUH

SUMMARY

A. Total Internal Heat Load = ERSHL + ERLHL = 48286.07 + 43679.25 =

Total Internal Heat Load = 91965.31 BTUH
B. Return Duct Heat Gain = 6% of A = 91965.31 BTUH x 6% = 5517.92 BTUH
C. Return Duct Leakage Losses = 3% of A = 91965.31 BTUH x 3%
Return Duct Leakage Losses = 2758.96 BTUH

Grand Total Internal Heat Load = Summation of A - C

= 91965.31 + 5517.92 + 2758.96
= 100242.19 BTUH

Total Room Heat Load = External Heat Load + GTIHL

= 10899.40 + 100242.19
= 111141.59 BTUH

TOTAL ROOM REQUIREMENT = 𝑇𝑅𝐻𝐿⁄12000 𝐵𝑇𝑈𝐻⁄𝑇𝑜𝑛𝑠

111141.59 𝐵𝑇𝑈𝐻
= 12000 𝐵𝑇𝑈𝐻
⁄𝑇𝑜𝑛𝑠

TOTAL ROOM REQUIREMENT = 9.262 TONS