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AC Sizing worksheet

Grades 6–7

Solve each problem and show your work. Round answers to 2 decimal places where needed.

1.
Problem 1.
- Area units: Square meters
- Floor area to cool: 52 m²
- Base cooling per square foot: 22 BTU/h per ft²
- Sun exposure: Average
- People who regularly use the space: 2
- The space includes a kitchen (+4,000 BTU/h): No
Find: Estimated cooling capacity
Answer
2.
Problem 2.
- Area units: Square feet
- Floor area to cool: 325 ft²
- Base cooling per square foot: 13 BTU/h per ft²
- Sun exposure: Average
- People who regularly use the space: 2
- The space includes a kitchen (+4,000 BTU/h): No
Find: Estimated cooling capacity
Answer
3.
Problem 3.
- Area units: Square meters
- Floor area to cool: 40 m²
- Base cooling per square foot: 24 BTU/h per ft²
- Sun exposure: Very sunny (+10%)
- People who regularly use the space: 2
- The space includes a kitchen (+4,000 BTU/h): No
Find: Estimated cooling capacity
Answer
4.
Problem 4.
- Area units: Square feet
- Floor area to cool: 330 ft²
- Base cooling per square foot: 22 BTU/h per ft²
- Sun exposure: Heavily shaded (−10%)
- People who regularly use the space: 2
- The space includes a kitchen (+4,000 BTU/h): No
Find: Estimated cooling capacity
Answer
5.
Problem 5.
- Area units: Square meters
- Floor area to cool: 50 m²
- Base cooling per square foot: 16 BTU/h per ft²
- Sun exposure: Heavily shaded (−10%)
- People who regularly use the space: 3
- The space includes a kitchen (+4,000 BTU/h): No
Find: Estimated cooling capacity
Answer
6.
Problem 6.
- Area units: Square feet
- Floor area to cool: 480 ft²
- Base cooling per square foot: 16 BTU/h per ft²
- Sun exposure: Heavily shaded (−10%)
- People who regularly use the space: 2
- The space includes a kitchen (+4,000 BTU/h): No
Find: Estimated cooling capacity
Answer
7.
Problem 7.
- Area units: Square meters
- Floor area to cool: 28 m²
- Base cooling per square foot: 18 BTU/h per ft²
- Sun exposure: Heavily shaded (−10%)
- People who regularly use the space: 1
- The space includes a kitchen (+4,000 BTU/h): No
Find: Estimated cooling capacity
Answer
8.
Problem 8.
- Area units: Square feet
- Floor area to cool: 380 ft²
- Base cooling per square foot: 18 BTU/h per ft²
- Sun exposure: Heavily shaded (−10%)
- People who regularly use the space: 2
- The space includes a kitchen (+4,000 BTU/h): No
Find: Estimated cooling capacity
Answer
9.
Problem 9.
- Area units: Square feet
- Floor area to cool: 460 ft²
- Base cooling per square foot: 24 BTU/h per ft²
- Sun exposure: Heavily shaded (−10%)
- People who regularly use the space: 1
- The space includes a kitchen (+4,000 BTU/h): No
Find: Estimated cooling capacity
Answer
10.
Problem 10.
- Area units: Square meters
- Floor area to cool: 45 m²
- Base cooling per square foot: 20 BTU/h per ft²
- Sun exposure: Average
- People who regularly use the space: 2
- The space includes a kitchen (+4,000 BTU/h): No
Find: Estimated cooling capacity
Answer

Answer key: AC Sizing worksheet

1. Estimated cooling capacity: 12,314 BTU/h
1. Change the area to square feet, because the rule of thumb works per square foot (1 ft² = 0.09290304 m²)
  $\frac{52 m²}{0.09290304}$ $= 559.723342 ft²$
2. Start with the base load: the floor area times the cooling needed for each square foot
  $559.723342 \times 22$ $= 12,313.913517 BTU/h$
3. Add 600 BTU/h of body heat for each person beyond the first two (0 extra)
  $0 \times 600$ $= 0 BTU/h$
4. Add it all up: the adjusted base plus the people (no kitchen to add)
  $12,313.913517 + 0 + 0$ $= 12,313.913517 BTU/h$
5. Change to tons, the unit central systems are sold in (1 ton = 12,000 BTU/h)
  $\frac{12,313.913517}{12,000}$ $= 1.026159 tons$
2. Estimated cooling capacity: 4,225 BTU/h
1. Start with the base load: the floor area times the cooling needed for each square foot
  $325 \times 13$ $= 4,225 BTU/h$
2. Add 600 BTU/h of body heat for each person beyond the first two (0 extra)
  $0 \times 600$ $= 0 BTU/h$
3. Add it all up: the adjusted base plus the people (no kitchen to add)
  $4,225 + 0 + 0$ $= 4,225 BTU/h$
4. Change to tons, the unit central systems are sold in (1 ton = 12,000 BTU/h)
  $\frac{4,225}{12,000}$ $= 0.352083 tons$
3. Estimated cooling capacity: 11,367 BTU/h
1. Change the area to square feet, because the rule of thumb works per square foot (1 ft² = 0.09290304 m²)
  $\frac{40 m²}{0.09290304}$ $= 430.556417 ft²$
2. Start with the base load: the floor area times the cooling needed for each square foot
  $430.556417 \times 24$ $= 10,333.354 BTU/h$
3. Add 10% because strong sun heats a very sunny space
  $10,333.354 \times 1.1$ $= 11,366.6894 BTU/h$
4. Add 600 BTU/h of body heat for each person beyond the first two (0 extra)
  $0 \times 600$ $= 0 BTU/h$
5. Add it all up: the adjusted base plus the people (no kitchen to add)
  $11,366.6894 + 0 + 0$ $= 11,366.6894 BTU/h$
6. Change to tons, the unit central systems are sold in (1 ton = 12,000 BTU/h)
  $\frac{11,366.6894}{12,000}$ $= 0.947224 tons$
4. Estimated cooling capacity: 6,534 BTU/h
1. Start with the base load: the floor area times the cooling needed for each square foot
  $330 \times 22$ $= 7,260 BTU/h$
2. Take off 10% because a heavily shaded space gets less heat from the sun
  $7,260 \times 0.9$ $= 6,534 BTU/h$
3. Add 600 BTU/h of body heat for each person beyond the first two (0 extra)
  $0 \times 600$ $= 0 BTU/h$
4. Add it all up: the adjusted base plus the people (no kitchen to add)
  $6,534 + 0 + 0$ $= 6,534 BTU/h$
5. Change to tons, the unit central systems are sold in (1 ton = 12,000 BTU/h)
  $\frac{6,534}{12,000}$ $= 0.5445 tons$
5. Estimated cooling capacity: 8,350 BTU/h
1. Change the area to square feet, because the rule of thumb works per square foot (1 ft² = 0.09290304 m²)
  $\frac{50 m²}{0.09290304}$ $= 538.195521 ft²$
2. Start with the base load: the floor area times the cooling needed for each square foot
  $538.195521 \times 16$ $= 8,611.128333 BTU/h$
3. Take off 10% because a heavily shaded space gets less heat from the sun
  $8,611.128333 \times 0.9$ $= 7,750.0155 BTU/h$
4. Add 600 BTU/h of body heat for each person beyond the first two (1 extra)
  $1 \times 600$ $= 600 BTU/h$
5. Add it all up: the adjusted base plus the people (no kitchen to add)
  $7,750.0155 + 600 + 0$ $= 8,350.0155 BTU/h$
6. Change to tons, the unit central systems are sold in (1 ton = 12,000 BTU/h)
  $\frac{8,350.0155}{12,000}$ $= 0.695835 tons$
6. Estimated cooling capacity: 6,912 BTU/h
1. Start with the base load: the floor area times the cooling needed for each square foot
  $480 \times 16$ $= 7,680 BTU/h$
2. Take off 10% because a heavily shaded space gets less heat from the sun
  $7,680 \times 0.9$ $= 6,912 BTU/h$
3. Add 600 BTU/h of body heat for each person beyond the first two (0 extra)
  $0 \times 600$ $= 0 BTU/h$
4. Add it all up: the adjusted base plus the people (no kitchen to add)
  $6,912 + 0 + 0$ $= 6,912 BTU/h$
5. Change to tons, the unit central systems are sold in (1 ton = 12,000 BTU/h)
  $\frac{6,912}{12,000}$ $= 0.576 tons$
7. Estimated cooling capacity: 4,883 BTU/h
1. Change the area to square feet, because the rule of thumb works per square foot (1 ft² = 0.09290304 m²)
  $\frac{28 m²}{0.09290304}$ $= 301.389492 ft²$
2. Start with the base load: the floor area times the cooling needed for each square foot
  $301.389492 \times 18$ $= 5,425.01085 BTU/h$
3. Take off 10% because a heavily shaded space gets less heat from the sun
  $5,425.01085 \times 0.9$ $= 4,882.509765 BTU/h$
4. Add 600 BTU/h of body heat for each person beyond the first two (0 extra)
  $0 \times 600$ $= 0 BTU/h$
5. Add it all up: the adjusted base plus the people (no kitchen to add)
  $4,882.509765 + 0 + 0$ $= 4,882.509765 BTU/h$
6. Change to tons, the unit central systems are sold in (1 ton = 12,000 BTU/h)
  $\frac{4,882.509765}{12,000}$ $= 0.406876 tons$
8. Estimated cooling capacity: 6,156 BTU/h
1. Start with the base load: the floor area times the cooling needed for each square foot
  $380 \times 18$ $= 6,840 BTU/h$
2. Take off 10% because a heavily shaded space gets less heat from the sun
  $6,840 \times 0.9$ $= 6,156 BTU/h$
3. Add 600 BTU/h of body heat for each person beyond the first two (0 extra)
  $0 \times 600$ $= 0 BTU/h$
4. Add it all up: the adjusted base plus the people (no kitchen to add)
  $6,156 + 0 + 0$ $= 6,156 BTU/h$
5. Change to tons, the unit central systems are sold in (1 ton = 12,000 BTU/h)
  $\frac{6,156}{12,000}$ $= 0.513 tons$
9. Estimated cooling capacity: 9,936 BTU/h
1. Start with the base load: the floor area times the cooling needed for each square foot
  $460 \times 24$ $= 11,040 BTU/h$
2. Take off 10% because a heavily shaded space gets less heat from the sun
  $11,040 \times 0.9$ $= 9,936 BTU/h$
3. Add 600 BTU/h of body heat for each person beyond the first two (0 extra)
  $0 \times 600$ $= 0 BTU/h$
4. Add it all up: the adjusted base plus the people (no kitchen to add)
  $9,936 + 0 + 0$ $= 9,936 BTU/h$
5. Change to tons, the unit central systems are sold in (1 ton = 12,000 BTU/h)
  $\frac{9,936}{12,000}$ $= 0.828 tons$
10. Estimated cooling capacity: 9,688 BTU/h
1. Change the area to square feet, because the rule of thumb works per square foot (1 ft² = 0.09290304 m²)
  $\frac{45 m²}{0.09290304}$ $= 484.375969 ft²$
2. Start with the base load: the floor area times the cooling needed for each square foot
  $484.375969 \times 20$ $= 9,687.519375 BTU/h$
3. Add 600 BTU/h of body heat for each person beyond the first two (0 extra)
  $0 \times 600$ $= 0 BTU/h$
4. Add it all up: the adjusted base plus the people (no kitchen to add)
  $9,687.519375 + 0 + 0$ $= 9,687.519375 BTU/h$
5. Change to tons, the unit central systems are sold in (1 ton = 12,000 BTU/h)
  $\frac{9,687.519375}{12,000}$ $= 0.807293 tons$