Frederick H. Rohles

Thermal Sensations of Sedentary Man in Moderate Temperatures

To determine the full range of thermal conditions at which sedentary subjects report feeling comfortable, 1600 college age students were exposed in groups of 10 subjects each, five men and five women, to 20 dry-bulb temperatures ranging from 60 to 98°F. in increments of 2° F. at each of eight relative humidities: 15, 25, 35, 45, 55, 65, 75, and 85%; subjects were required to report their thermal sensations on a 7-point scale every half-hour. The results showed that for sedentary subjects exposed for three hours in standard clothing with an insulative value of 0.6 clo., the “comfortable” votes were distributed over the temperature range of 62 to 98°F. In addition, it was found that at a given temperature men feel warmer than women during the first hour and that humidity plays a significantly more important role in how men feel than in how women feel. Regression equations are presented for predicting thermal sensations for various dry-bulb temperatures and relative humidities.

Opening Jars: An Anthropometric Study of the Wrist-Twisting Strength of the Elderly

The purpose of this study was to measure the wrist-twisting strength among the elderly. The subjects were 100 men and 100 women whose ages ranged from 62 to 92 years. To measure their wrist-twisting strength a device was developed that consisted of a modified torque-wrench which would accept 8 different container lids whose diameters ranged from 27 mm to 123 mm. Each subject performed the wrist-twisting task on each lid 4 times – twice clockwise and twice counter-clockwise. The results showed that men were stronger than the women, that there was no difference in the torque from a clockwise or a counter-clockwise twist, and that a greater amount of torque could be applied to large diameter lids than to smaller diameter lids. When age, body weight, height, grasp, lateral prehension, and hand length, breadth, and spread were correlated with the wrist-twisting strength it was found that for the men, age, grasp and hand length contributed to torque and for the women, body weight, grasp, and lateral prehension were the main determinants of torque. In addition the torque required to open various commercial products was measured so that by comparing these torque values with those of the wrist-twisting strength it was able to estimate the percentage of men and women who could open a jar of a given diameter and torque.

Plants as enhancers of the indoor environment

Sixty-four subjects (32 men and 32 women) evaluated environmental quality and thermal comfort in a 2 − 2 design involving 2 temperature conditions, 20.0°C (68°F) and 25.6°C (78°F), within a climate controlled chamber that was either decorated with plants or was devoid of plants. The results showed that on a scale developed for measuring Occupied Space Quality, a higher rating accompanied the condition in which plants were used to enhance the environment than the condition in which no plants were used. The plants, however, did not affect the subjective thermal responses.

Quantifying the thermal protection characteristics of outdoor clothing systems.

This paper describes a reliable test method for measuring and comparing the heat-transfer characteristics of outdoor garments and sleeping bags. The procedure involves the use of an electrically heated mannequin located in a climate-controlled chamber. Unlike instruments that evaluate small samples of fabric, the mannequin technique reflects the effects of fabric overlap and garment design, shape, fit, and layering in the measurements. This paper also discusses the textile and human factors that affect the heat exchange between the body and a cold environment.

A Scaling Procedure for Environmental Research

Drawing upon the scaling techniques of Osgood, Suci, and Tannenbaum and the factor analytic methods of Flynn, and Mehrabian and Russell, a scaling procedure is presented that will permit the researcher to evaluate the affective characteristics of the environment and various features it contains. Starting with a large number of adjective-pairs in a semantic-differential format, an analysis of variance is computed from the responses to each adjective-pair, residuals are computed, and a correlation matrix is developed. A factor analysis of the correlation matrix yields the “attributes” being measured and the weights for each adjective-pair. The scale is then re-scored using these weights and the resulting values serve as dependent variables for a conventional analysis of variance. Examples of scales for measuring thermal comfort, environmental spaciousness, efficiency, attractiveness, and overall quality will be presented as well as scales that have been developed for measuring the size, style and comfort of office chairs, the comfort characteristics of protective clothing, and the style and acceptance of mixing valves used in showers. A step-by-step procedure for the statistically unsophisticated individual is presented.

The Modal Comfort Envelope and its Use in Current Standards

A detailed study of thermal comfort was conducted by exposing 1600 subjects, in groups of 10 subjects each (5 men and 5 women), to 20 dry bulb temperatures at each of eight relative humidities (160 tests). From this study, 15 temperature-humidity conditions were selected (ET: 75.9-79.7°F) and identified as the Modal Comfort Envelope (MCE). Within this envelope 94% of the subjects were either slightly cool, comfortable, or slightly warm; 3% were cool and 3% were warm; and none were hot or cold. To validate these findings, a new sample of 150 subjects was tested and the results of this test agree favorably with the original findings. The MCE was used in a clothing study and in an investigation of thermal comfort in the elderly; the results of these studies are discussed, together with suggestions for the use of the Modal Comfort Envelope, as a tool for examining the thermal sensation as a function of such non-thermal factors as lighting, subject density, sex, and activity. A slightly modified version of the MCE is currently being used as a standard for thermal comfort by ASHRAE and this is examined together with ASHRAE Comfort Standard 55–66, the New ASHRAE Comfort Chart, and the new Effective Temperature Scale.

Hunger as a catalyst in aggression.

Under thermal conditions of 90° F 50% RH and a subject density of I subject per 0.125 sq. ft, two strains of inbred mice, C-57 (aggressive) and A/J (docile) were tested for aggressive behaviour following food deprivation periods of 0, 24, 36, and 48 hours. The greatest amount of aggression occurred in the 24 hours deprivation group of C-57 subjects whereas the 36 hour hungry A/J animals were most aggressive. Metabolism as evidenced by activity level and extent of food deprivation is suggested as the primary determinant of aggressive behaviour when temperature and subject-density are held constant.

The Effect of Time of Day and Time of Year on Thermal Comfort

In order to determine if affective responses to cool, neutral, and warm temperatures were related to the season of the year and the time of day, 108 subjects were exposed in groups of six (3 males and 3 females) for 3 hours to three temperatures 20.0°C, 25.6°C and 31.7°C at 50%rh during the morning (0900–1200) afternoon (1300–1600) and evening (1800–2100) in the summer and winter. The subjects were sedentary and wore similar clothing; a 9 category Thermal Sensation ballot and a 7-pair semantic differential scale for measuring Thermal Comfort were administered every half hour during the three hour exposure. An analysis of variance showed that the main effects, Time of Day, Sex and Season were not significant and only Temperature and Voting were significant; both measures showed significant Season x Temperature interactions. Basically, the 20.0°C environment was judged to be more comfortable in the summer than in the winter and the 31.7°C environment was judged to be more comfortable in the winter than in the summer. The seasonal findings are opposite to those found in recent research and suggest that different temperature criteria for thermal comfort should be considered for summer and winter conditions.

Spontaneous (accidental) hypothermia in the elderly

Oral temperatures were taken under field conditions on 730 elderly persons whose ages ranged from 60 to 94 years. The mean temperature of the sample was 36.4 °C (97.5°F). Compared with the British national survey, which numbered 1,020 cases, 3.4% of the cases were hypothermic (temperature ⩽ 35°C, or 95°F), whereas 5.1% of the British sample had temperatures at this level.

Conserving Energy by Expanding the Thermal Comfort Envelope

Standard 55–74 entitled “Thermal Conditions for Human Occupancy” which is published by The American Society of Heating, Refrigerating, and Air Conditioning Engineers, (ASHRAE) defines an “acceptable thermal environment” as one in which “at least 80 percent of the normally clothed men and women while engaged in indoor sedentary or near sedentary activities would express thermal comfort.” This is pictured on the ASHRAE psychrometric chart as an envelope that includes dry bulb temperatures between 74°F and 77°F at relative humidities between 20% and 60%. The paper will describe five human factors approaches that have been used or are being considered to expand this envelope and thereby conserve energy. These are (1) the use of small radiant heaters which are installed in the modesty panels of desks so comfort may be attained at lower temperatures; (2) the demonstration that night set-back of thermostats to temperatures as low as 50°F do not effect sleeping patterns; (3) the role that interior decor can play in making people feel warmer; (4) the effect that temperature “swings” associated with solar heating and cooling has upon acceptance of the thermal environment and (5) the acceptance of a reduced quality of indoor air as a result of heating with an increased ratio of recirculated air to outside air.