Thermal Comfort Factors

Metabolic Rate

The metabolic rate characterizes the energy generated inside the body due to metabolic activity. The standard unit for metabolic rate is the met.

1 met = 58.2 W/m² (18.4 BTU /h ft²).

A single met is approximately the amount of energy produced per unit surface area of a person of average stature, seated at rest. (The surface area of the average person is about 1.8 m² (19 ft²). The Autodesk® CFD units of Metabolic rate are W/m², and the default value is 60 W/m².

Note that this value must be specified in addition to the heat generation boundary condition applied to each human form. (The heat generation boundary condition is needed to compute an accurate temperature solution. Autodesk® CFD uses both the temperature distribution and the specified Metabolic rate factor to compute the thermal comfort.)

Metabolic rates for several activities and situations

Activity	Metabolic Rate (W/m²)
Sleeping	40
Reclining	45
Sitting quietly	60
Standing	70

Walking slowly (0.9 m/s, 3.2 km/h, 2.0 mph)	115
Walking moderately (1.2 m/s, 4.3 km/h, 2.7 mph)	150
Walking briskly (1.8 m/s, 6.8 km/h, 4.2 mph)	220

Seated, reading, or writing	60
Typing	65
Filing (seated)	70
Filing (standing)	80
Walking about an office	100
Lifting/packing	120

Dancing	140-255
Exercise / calisthenics	175-235
Playing tennis	210-270
Playing basketball	290-440

Clothing

The clothing worn by the occupant plays a significant role in the perceived thermal comfort level. A heavy coat in the middle of summer is very uncomfortable, but is quite appropriate in winter!

Clothing is quantitatively expressed in units of "clo." A clo is the thermal insulation provided by garments and clothing ensembles:

1 clo = 0.155 m2 °C/W (0.88 ft2·h·°F/Btu).

Clo value table for a variety of clothing ensembles

Clothing Ensemble	clo value
Trousers and short-sleeve shirt	0.57
Trousers and long-sleeve shirt	0.61
Trousers, long-sleeve shirt, and suit jacket	0.96
Trousers, long-sleeve shirt, suit jacket, vest, and T-shirt	1.14
Trousers, long-sleeve shirt, long-sleeve sweater, and T-shirt	1.01
Trousers, long-sleeve shirt, long-sleeve sweater, T-shirt, suit jacket, and long underwear bottoms	1.30

Knee-length skirt and short-sleeve shirt, with sandals	0.54
Knee-length skirt, long-sleeve shirt, and full slip	0.67
Knee-length skirt, long-sleeve shirt, half slip, and long-sleeve sweater	1.10
Knee-length skirt, long-sleeve shirt, half slip, and suit jacket	1.04
Ankle-length skirt, long-sleeve shirt, and suit jacket	1.10

Walking shorts and short-sleeve shirt	0.36

Long-sleeve coveralls and T-shirt	0.72
Overalls, long-sleeve shirt, and T-shirt	0.89
Insulated coveralls, long-sleeve thermal underwear tops and bottoms	1.37

Sweat pants and long-sleeve sweatshirt	0.74

Long-sleeve pajama tops, long pajama trousers, short 3/4 length robe (slippers, no socks)	0.96

All clothing ensembles, except where noted, include shoes, socks, and briefs or panties. All skirt/dress ensembles include pantyhose and no additional socks.

Humidity

Specify the relative humidity (as a percentage) of the room or space.