HVAC Rule of Thumb CFM/sf

Space External Cooling Load Assumptions

Climate Zone

Example City

Cooling Load (Btuh/sf)

Airlfow required to meet external load at 74 °F space temperature and 55 °F supply air temperature (CFM/sf)

1

Miami, FL

17.76

0.87

2

Midland, TX

14.34

0.70

3

Vance AFB, OK

10.92

0.53

4

St. Louis, MO

7.50

0.37

5

Omaha, NE

6.22

0.30

6

Sioux Falls , SD

4.94

0.24

7

Minot AFB, ND

3.66

0.18

8

Fairbanks, AL

2.37

0.12

.

Space Heating Load Assumptions

Climate Zone

Example City

Heating Load (Btuh/sf)

Required DA-T at 0.5 CFM/sf and 70 °F Space Temperature (°F )

1

Miami, FL

3.79

77.0

2

Midland, TX

6.74

82.5

3

Vance AFB, OK

9.68

87.9

4

St. Louis, MO

12.62

93.4

5

Omaha, NE

14.24

96.4

6

Sioux Falls , SD

15.86

99.4

7

Minot AFB, ND

17.48

102.4

8

Fairbanks, AL

19.09

105.4

.

Quick Load Default Assumptions (55 °F Supply Air Temperature)

Space Type

Internal Loads and Airflow (Default assumptions can be changed in Revit-> Manage Tab -> MEP Settings -> Building/Space Type Settings -> Space Types)

Internal + External Airflow (CFM/sf)

Cooling Mode Space Temperature Setpoint (°F)

Occupant Density (people per 1000 sf)

Sensible Heat Gain Per Person (Btuh per person)

Lighting Load Density (W/sf)

Power Load Density (W/sf)

Internal Sensible Load (Btuh/sf)

LTK-Provide AHU Supply Air

Internal CFM/sf

Zone 1 CFM/sf

Zone 2 CFM/sf

Zone 3 CFM/sf

Zone 4 CFM/sf

Zone 5 CFM/sf

Zone 6 CFM/sf

Zone 7 CFM/sf

Zone 8 CFM/sf

Space Type Unassigned/<Building>/(LTK-Load-Default Building)

74

25

275

0.8

1

13.02

true

0.63

1.50

1.33

1.17

1.00

0.94

0.88

0.81

0.75

LTK-Load-RA Plenum Space

78

0

0

0

0

0.00

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-Correctional Facilites – Booking/waiting

74

50

375

0.75

0.25

22.16

true

1.08

1.95

1.78

1.61

1.45

1.38

1.32

1.26

1.20

LTK-Load-Correctional Facilites – Cell

74

25

375

0.75

0.25

12.79

true

0.62

1.49

1.32

1.16

0.99

0.93

0.86

0.80

0.74

LTK-Load-Correctional Facilites – Cell With Toilet

74

25

375

0.75

0.25

12.79

true

0.62

1.49

1.32

1.16

0.99

0.93

0.86

0.80

0.74

LTK-Load-Correctional Facilites – Dayroom

74

30

375

0.75

0.25

14.66

true

0.71

1.58

1.41

1.25

1.08

1.02

0.96

0.89

0.83

LTK-Load-Correctional Facilites – Guard stations

74

15

375

0.75

0.25

9.04

true

0.44

1.31

1.14

0.97

0.81

0.74

0.68

0.62

0.56

LTK-Load-Educational Facilities – Art classroom

74

20

275

0.81

0.5

9.97

true

0.49

1.35

1.18

1.02

0.85

0.79

0.73

0.66

0.60

LTK-Load-Educational Facilities – Classrooms (age 9 plus)

74

35

275

0.81

0.5

14.09

true

0.69

1.55

1.39

1.22

1.05

0.99

0.93

0.87

0.80

LTK-Load-Educational Facilities – Classrooms (ages 5–8)

74

25

275

0.81

0.5

11.34

true

0.55

1.42

1.25

1.09

0.92

0.86

0.79

0.73

0.67

LTK-Load-Educational Facilities – Computer lab

74

25

275

0.81

0.5

11.34

true

0.55

1.42

1.25

1.09

0.92

0.86

0.79

0.73

0.67

LTK-Load-Educational Facilities – Daycare (through age 4)

74

25

275

0.81

0.5

11.34

true

0.55

1.42

1.25

1.09

0.92

0.86

0.79

0.73

0.67

LTK-Load-Educational Facilities – Daycare sickroom

74

25

275

0.81

0.5

11.34

true

0.55

1.42

1.25

1.09

0.92

0.86

0.79

0.73

0.67

LTK-Load-Educational Facilities – Lecture classroom

74

65

275

0.81

0.5

22.34

true

1.09

1.95

1.79

1.62

1.45

1.39

1.33

1.27

1.20

LTK-Load-Educational Facilities – Lecture hall (fixed seats)

74

150

275

0.81

0.25

44.87

true

2.19

3.05

2.89

2.72

2.55

2.49

2.43

2.36

2.30

LTK-Load-Educational Facilities – Media center

74

25

275

0.81

0.25

10.49

true

0.51

1.38

1.21

1.04

0.88

0.81

0.75

0.69

0.63

LTK-Load-Educational Facilities – Multi-use assembly

74

100

375

0.81

0.25

41.12

true

2.00

2.87

2.70

2.54

2.37

2.31

2.24

2.18

2.12

LTK-Load-Educational Facilities – Music/theater/dance classrooms (Not Stages)

74

35

710

0.81

0.25

28.47

true

1.39

2.25

2.09

1.92

1.75

1.69

1.63

1.57

1.50

LTK-Load-Educational Facilities – Science laboratories

74

25

375

1.2

3

23.71

true

1.16

2.02

1.85

1.69

1.52

1.46

1.40

1.33

1.27

LTK-Load-Educational Facilities – Wood/metal shop

74

20

375

0.9

3

20.81

true

1.01

1.88

1.71

1.55

1.38

1.32

1.25

1.19

1.13

LTK-Load-Food and Beverage Service – Bars, cocktail lounges

74

100

275

0.9

0.1

30.91

true

1.51

2.37

2.21

2.04

1.87

1.81

1.75

1.68

1.62

LTK-Load-Food and Beverage Service – Cafeteria/fast-food dining

74

100

275

0.79

0.1

30.54

true

1.49

2.35

2.19

2.02

1.85

1.79

1.73

1.67

1.60

LTK-Load-General – Kitchenettes

74

0

275

0.9

0.5

4.78

true

0.23

1.10

0.93

0.77

0.60

0.54

0.47

0.41

0.35

LTK-Load-Food and Beverage Service – Kitchen (cooking)

78

20

710

2

7

44.91

true

1.81

2.52

2.39

2.25

2.11

2.06

2.01

1.96

1.90

LTK-Load-Food and Beverage Service – Restaurant dining rooms

74

70

275

0.79

0.1

22.29

true

1.09

1.95

1.79

1.62

1.45

1.39

1.33

1.26

1.20

LTK-Load-General – Break rooms

74

25

275

0.9

0.5

11.65

true

0.57

1.43

1.27

1.10

0.93

0.87

0.81

0.75

0.68

LTK-Load-General – Coffee stations

74

20

275

0.9

0.5

10.28

true

0.50

1.37

1.20

1.03

0.87

0.80

0.74

0.68

0.62

LTK-Load-General – Conference/meeting

74

50

275

1.07

0.75

19.96

true

0.97

1.84

1.67

1.51

1.34

1.28

1.21

1.15

1.09

LTK-Load-General – Copy, Printing Rooms

74

0

275

0.46

0.1

1.91

true

0.09

0.96

0.79

0.63

0.46

0.40

0.33

0.27

0.21

LTK-Load-General – Corridors

74

0

275

0.66

0.1

2.59

true

0.13

0.99

0.83

0.66

0.49

0.43

0.37

0.30

0.24

LTK-Load-General – Electrical equipment rooms

74

0

275

0.43

15

52.65

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-General – Elevator machine rooms

74

0

275

0.43

15

52.65

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-General – Janitor Closet, Trash Rooms, Recycling

74

0

275

0.46

0.1

1.91

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-General – Locker rooms for all other (non-athletic, non-industrial, and non-health care facilities).

74

0

275

0.85

0.5

4.61

true

0.22

1.09

0.92

0.76

0.59

0.53

0.47

0.40

0.34

LTK-Load-General – Locker rooms for athletic, industrial, and health care facilities.

74

0

275

0.85

0.5

4.61

true

0.22

1.09

0.92

0.76

0.59

0.53

0.47

0.40

0.34

LTK-Load-General – Mechanical Equipment Room

78

0

275

0.46

15

52.75

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-General – Occupiable storage rooms for liquids or gels

74

2

275

0.46

0.1

2.46

true

0.12

0.99

0.82

0.65

0.49

0.42

0.36

0.30

0.24

LTK-Load-General – Storage rooms

78

0

275

0.46

0.1

1.91

true

0.08

0.79

0.65

0.52

0.38

0.33

0.28

0.22

0.17

LTK-Load-Office Buildings – Occupiable storage rooms for dry materials

74

2

275

0.48

0.5

3.89

true

0.19

1.06

0.89

0.72

0.56

0.49

0.43

0.37

0.31

LTK-Load-General – Shower Room

74

0

275

0.85

0.5

4.61

true

0.22

1.09

0.92

0.76

0.59

0.53

0.47

0.40

0.34

LTK-Load-General – Stairwell

78

0

710

0.58

0

1.98

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-General – Toilets – Private (Single User)

74

0

275

0.85

0.1

3.24

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-General – Toilets – Public (Multiple Users)

74

0

275

0.85

0.1

3.24

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-Hotels, Motels, Resorts, Dormitories – Barracks sleeping areas

74

20

275

0.2

0.25

7.04

true

0.34

1.21

1.04

0.88

0.71

0.65

0.58

0.52

0.46

LTK-Load-Hotels, Motels, Resorts, Dormitories – Bedroom/living room

74

10

275

0.2

0.25

4.29

true

0.21

1.07

0.91

0.74

0.57

0.51

0.45

0.39

0.32

LTK-Load-Hotels, Motels, Resorts, Dormitories – Laundry rooms within dwelling units

74

10

275

0.2

0.25

4.29

true

0.21

1.07

0.91

0.74

0.57

0.51

0.45

0.39

0.32

LTK-Load-Hotels, Motels, Resorts, Dormitories – Laundry rooms, central

74

10

275

0.43

0.25

5.07

true

0.25

1.11

0.95

0.78

0.61

0.55

0.49

0.43

0.36

LTK-Load-Hotels, Motels, Resorts, Dormitories – Lobbies/prefunction

74

30

275

1

0.25

12.52

true

0.61

1.48

1.31

1.14

0.98

0.91

0.85

0.79

0.73

LTK-Load-Hotels, Motels, Resorts, Dormitories – Multipurpose assembly

74

120

275

1.2

0.25

37.95

true

1.85

2.71

2.55

2.38

2.21

2.15

2.09

2.03

1.96

LTK-Load-Laboratory – Chemical Storage Room

74

0

275

0.48

0.5

3.34

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-Miscellaneous Spaces – Bank vaults/safe deposit

74

5

275

0.48

0.25

3.87

true

0.19

1.05

0.89

0.72

0.55

0.49

0.43

0.37

0.30

LTK-Load-Miscellaneous Spaces – Banks or bank lobbies

74

15

375

1

0.25

9.89

true

0.48

1.35

1.18

1.01

0.85

0.79

0.72

0.66

0.60

LTK-Load-Miscellaneous Spaces – Computer (not printing)

74

4

275

0.93

0.25

5.13

true

0.25

1.12

0.95

0.78

0.62

0.55

0.49

0.43

0.37

LTK-Load-Miscellaneous Spaces – Darkrooms

74

0

275

0.48

0.5

3.34

true

0.16

1.03

0.86

0.70

0.53

0.47

0.40

0.34

0.28

LTK-Load-Miscellaneous Spaces – Freezer and Refrigerated Spaces (less than 50 F)

65

0

275

0.9

0.25

3.92

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-Miscellaneous Spaces – General manufacturing (excludes heavy industrial and processes using chemicals)

74

7

710

0.9

0.25

8.89

true

0.43

1.30

1.13

0.97

0.80

0.74

0.67

0.61

0.55

LTK-Load-Miscellaneous Spaces – Paint Spray Booths

74

0

275

0.48

0.5

3.34

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-Miscellaneous Spaces – Parking Garages

78

0

275

0.15

0.5

2.22

false

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

LTK-Load-Miscellaneous Spaces – Pharmacy (prep. area)

74

10

375

1.34

0.25

9.18

true

0.45

1.31

1.15

0.98

0.81

0.75

0.69

0.63

0.56

LTK-Load-Miscellaneous Spaces – Photo studios

74

10

375

1.5

2

15.69

true

0.76

1.63

1.46

1.30

1.13

1.07

1.01

0.94

0.88

LTK-Load-Miscellaneous Spaces – Shipping/receiving

74

2

710

0.48

0.5

4.76

true

0.23

1.10

0.93

0.76

0.60

0.54

0.47

0.41

0.35

LTK-Load-Miscellaneous Spaces – Soiled Laundry Storage Rooms

74

0

275

0.43

0.5

3.17

true

0.15

1.02

0.85

0.69

0.52

0.46

0.40

0.33

0.27

LTK-Load-Miscellaneous Spaces – Sorting, packing, light assembly

74

7

710

0.48

3

16.84

true

0.82

1.69

1.52

1.35

1.19

1.12

1.06

1.00

0.94

LTK-Load-Miscellaneous Spaces – Telephone closets

74

0

275

0.48

0.5

3.34

true

0.16

1.03

0.86

0.70

0.53

0.47

0.40

0.34

0.28

LTK-Load-Miscellaneous Spaces – Transportation waiting

74

100

275

1.2

0.5

33.30

true

1.62

2.49

2.32

2.16

1.99

1.93

1.86

1.80

1.74

LTK-Load-Miscellaneous Spaces – Warehouses

78

0

275

0.48

0.5

3.34

true

0.13

0.85

0.71

0.57

0.44

0.39

0.33

0.28

0.23

LTK-Load-Office Buildings – Main entry lobbies

74

10

275

0.48

0.5

6.09

true

0.30

1.16

1.00

0.83

0.66

0.60

0.54

0.48

0.41

LTK-Load-Office Buildings – Office space

74

5

275

0.93

0.5

6.25

true

0.30

1.17

1.00

0.84

0.67

0.61

0.55

0.48

0.42

LTK-Load-Office Buildings – Open Office space

74

25

275

0.81

1.5

14.76

true

0.72

1.58

1.42

1.25

1.08

1.02

0.96

0.90

0.83

LTK-Load-Office Buildings – Reception areas

74

30

275

0.66

0.25

11.36

true

0.55

1.42

1.25

1.09

0.92

0.86

0.79

0.73

0.67

LTK-Load-Office Buildings – Telephone/data entry

74

60

275

0.48

0.5

19.84

true

0.97

1.83

1.67

1.50

1.33

1.27

1.21

1.15

1.08

LTK-Load-Public Assembly Spaces – Auditorium seating area

74

150

275

0.63

0.25

44.25

true

2.16

3.02

2.86

2.69

2.52

2.46

2.40

2.33

2.27

LTK-Load-Public Assembly Spaces – Courtrooms

74

70

275

0.9

0.25

23.17

true

1.13

1.99

1.83

1.66

1.49

1.43

1.37

1.31

1.24

LTK-Load-Public Assembly Spaces – Legislative chambers

74

50

275

0.9

0.25

17.67

true

0.86

1.73

1.56

1.39

1.23

1.16

1.10

1.04

0.98

LTK-Load-Public Assembly Spaces – Libraries

74

10

275

1.2

0.25

7.70

true

0.38

1.24

1.07

0.91

0.74

0.68

0.62

0.55

0.49

LTK-Load-Public Assembly Spaces – Lobbies

74

150

275

0.63

0.25

44.25

true

2.16

3.02

2.86

2.69

2.52

2.46

2.40

2.33

2.27

LTK-Load-Public Assembly Spaces – Museums (children’s)

74

40

275

1.05

0.25

15.44

true

0.75

1.62

1.45

1.28

1.12

1.06

0.99

0.93

0.87

LTK-Load-Public Assembly Spaces – Museums/galleries

74

40

275

1.05

0.25

15.44

true

0.75

1.62

1.45

1.28

1.12

1.06

0.99

0.93

0.87

LTK-Load-Public Assembly Spaces – Places of religious worship

74

120

275

0.94

0.25

37.06

true

1.81

2.67

2.51

2.34

2.17

2.11

2.05

1.98

1.92

LTK-Load-Residential – Common Corridors

74

0

275

0.61

0.25

2.93

true

0.14

1.01

0.84

0.68

0.51

0.45

0.38

0.32

0.26

LTK-Load-Residential – Dwelling unit

74

2

275

0.61

0.25

3.48

true

0.17

1.04

0.87

0.70

0.54

0.47

0.41

0.35

0.29

LTK-Load-Residential – Kitchen

74

0

275

2

0.25

7.68

true

0.37

1.24

1.07

0.91

0.74

0.68

0.61

0.55

0.49

LTK-Load-Retail – Auto Repair Shops

74

0

275

0.56

0.25

2.76

true

0.13

1.00

0.83

0.67

0.50

0.44

0.38

0.31

0.25

LTK-Load-Retail – Barbershop

74

25

275

1.06

0.25

11.34

true

0.55

1.42

1.25

1.09

0.92

0.86

0.79

0.73

0.67

LTK-Load-Retail – Beauty and nail salons

74

25

275

1.06

0.25

11.34

true

0.55

1.42

1.25

1.09

0.92

0.86

0.79

0.73

0.67

LTK-Load-Retail – Coin-operated laundries

74

20

275

1.06

0.25

9.97

true

0.49

1.35

1.18

1.02

0.85

0.79

0.73

0.66

0.60

LTK-Load-Retail – Mall common areas

74

40

275

1.06

0.25

15.47

true

0.75

1.62

1.45

1.29

1.12

1.06

0.99

0.93

0.87

LTK-Load-Retail – Pet shops (animal areas)

74

10

275

1.06

0.25

7.22

true

0.35

1.22

1.05

0.88

0.72

0.65

0.59

0.53

0.47

LTK-Load-Retail – Sales

74

15

275

1.06

0.25

8.59

true

0.42

1.28

1.12

0.95

0.78

0.72

0.66

0.60

0.53

LTK-Load-Retail – Supermarket

74

8

275

1.06

0.25

6.67

true

0.33

1.19

1.02

0.86

0.69

0.63

0.57

0.50

0.44

LTK-Load-Sports and Entertainment – Bowling alley (seating)

74

40

375

0.87

0.25

18.82

true

0.92

1.78

1.62

1.45

1.28

1.22

1.16

1.10

1.03

LTK-Load-Sports and Entertainment – Disco/dance floors

74

100

710

0.87

0.25

74.82

true

3.65

4.51

4.35

4.18

4.01

3.95

3.89

3.82

3.76

LTK-Load-Sports and Entertainment – Gambling casinos

74

120

375

0.87

0.25

48.82

true

2.38

3.24

3.08

2.91

2.74

2.68

2.62

2.56

2.49

LTK-Load-Sports and Entertainment – Game arcades

74

20

375

0.87

0.25

11.32

true

0.55

1.42

1.25

1.08

0.92

0.85

0.79

0.73

0.67

LTK-Load-Sports and Entertainment – Gym, stadium (play area)

74

30

710

0.87

0.25

25.12

true

1.22

2.09

1.92

1.76

1.59

1.53

1.46

1.40

1.34

LTK-Load-Sports and Entertainment – Health club/aerobics room

74

40

710

0.87

0.25

32.22

true

1.57

2.44

2.27

2.10

1.94

1.87

1.81

1.75

1.69

LTK-Load-Sports and Entertainment – Health club/weight rooms

74

10

710

0.87

0.25

10.92

true

0.53

1.40

1.23

1.06

0.90

0.84

0.77

0.71

0.65

LTK-Load-Sports and Entertainment – Spectator areas

74

150

275

0.87

0.25

45.07

true

2.20

3.06

2.90

2.73

2.56

2.50

2.44

2.37

2.31

LTK-Load-Sports and Entertainment – Sports arena (play area)

74

7

710

0.87

0.25

8.79

true

0.43

1.29

1.13

0.96

0.79

0.73

0.67

0.61

0.54

LTK-Load-Sports and Entertainment – Stages, studios

74

70

710

0.87

0.25

53.52

true

2.61

3.47

3.31

3.14

2.97

2.91

2.85

2.79

2.72

LTK-Load-Sports and Entertainment – Swimming (pool & deck)

74

0

710

0.87

0.25

3.82

true

0.19

1.05

0.89

0.72

0.55

0.49

0.43

0.36

0.30

.