Page 223 - Industrial Ventilation Design Guidebook

I 84 CHAPTER 5 PHYSIOLOGICAL AND TOXICOLOGICAL CONSIDERATIONS

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Some clothing item clo values are listed in Table 5.4. For example, the clo
value of a person wearing a thin shirt, thin trousers, underwear, shoes, and socks
estimated by this method would be: 0.17 + 0.25 + 0.05 + 0.05 = 0.52 clo. If
the person were to add a T-shirt under the shirt, the clothing insulation would be
expected to increase to 0.6 clo.

Effect of Chairs on Clothing Insulation
When a person is sitting, the chair generally has the effect of increasing
clothing insulation (AI cl) by up to 0.15 clo depending on the contact area
(CSAC) between the chair and body. Specifically,

2
where CSAC is the chair surface area contact in cm or the surface area of the
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chair in contact with the human. '
2
For example, a desk chair with a body contact area of 2700 cm has a AI cl
of 0.1 clo. This amount should be added to the insulation of the standing
clothing ensemble to obtain the insulation of the ensemble when a person is
sitting in the desk chair,

Effect of Walking on Clothing Insulation
Body motion generally increases the ventilation of garments and thereby
carries away heat and decreases the clothing ensemble's effective insulation.
The increased airflow between the garment and the skin is due to a combina-
tion of increased air speed and the pumping action of the garment as it flexes
during movement. As a result, walking decreases clo. The change in clothing
insulation (A/ clw) can be estimated from the standing intrinsic insulation of the
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ensemble (clo standing) and the walking speed (S) in steps per minute: -

Thus the insulation of the walking person is found by subtracting the walking
effect from the insulation of the standing clothing ensemble,

For example, the clothing insulation of a person wearing a winter business
suit with a standing intrinsic insulation of 1 clo would decrease by 0.52 cio
when the person walks at 90 steps per minute (about 3.7 km/h). Thus the en-
semble's intrinsic insulation when walking would be 0.48 clo. More complete
clothing tables and figures are available in the literature, for example Chapter
8 of the ASHRAE Handbook of Fundamentals . 6

5.1.5 Comfort Zones
In general, when a person is thermally comfortable, the person's thermal sen-
sation for the whole body is at or near neutral as depicted in Fig. 5.7(3. As we
have seen, the thermal conditions necessary for comfort are affected by cloth-
ing insulation. Figure 5.7b shows the range of temperatures and humidities