A comparison of methods for assessing the thermal insulation value of children's schoolwear in Kuwait

In this study, three methods were used to determine the thermal insulation values of different school clothing worn by 6 to 17 year old girls and boys in Kuwait classrooms for both summer and winter seasons. The different clothing ensembles' insulations were determined by 1: measurement using adult-sized versions of the clothing on thermal manikins, 2: estimations from adult clothing data obtained from the standards tables in ISO 9920 and ASHRAE 55, and 3: calculations using a regression equation from McCullough et al. (1985) that was adapted to accommodate children's sizes for ages 6-17 years. Values for the clothing area factor, f(cl), were also determined by measurement and by using a prediction equation from ISO 9920. Results in this study suggested that the clothing insulation values found from the measured and adapted data were similar to the adult's data in standards tables for the same summer and winter seasons. Further, the effect of the insulation values on the different scholars' age groups were investigated using the clothing temperature rating technique and compared to the scholars' comfort temperature found in recent field studies. Results showed that the temperature ratings of the clothing using the three methods described above are close and in agreement with the scholars' comfort temperature. Though estimated and measured f(cl) data differed, the impact on the temperature ratings was limited. An observed secular change in the children's heights and weights in the last few decades implies that, for adolescents, the children's body surface areas are similar to those of adults, making the use of adult clothing tables even more acceptable. In conclusion, this study gives some evidence to support the applicability of using adults' data in ASHRAE 55 and ISO 9920 standards to assess the thermal insulation values of different children's clothing ensembles, provided that careful selection of the garments, ensembles material and design takes place.     

Comparison between required clothing insulation and that actually worn by workers exposed to artificial cold

Required Clothing Insulation (IREQ) is a new thermal index submitted to the International Organisation for Standardisation (ISO) for discussion. It is designed to prevent general body cooling and is based on an analysis of heat exchanges. The thermal clothing insulation actually worn (lcl) is estimated using a new method, also submitted to ISO.

IREQ of 54 workers exposed to artificial cold (air temperature between −30° C and +10° C) was compared with lcl actually worn by these workers. The results of the present study show that, on average, the workers choose accurately lcl they need if their IREQ is below and up to 1·5 clo. Moreover, these workers prefer to wear garments which provide them with thermal comfort. If IREQ of workers is higher than 1·5–2 clo (i e, workers exposed to −20° C), it is difficult for them to increase their thermal insulation with additional garments. Although their lcl is not sufficient, there is no risk of gradual body cooling because of their continuous time exposure (CTE) which is shorter than the calculated Duration Limited Exposure (DLE). On the other hand, Wind Chill Index (WCI), which is proposed to prevent local cooling, is better adapted to prevent cold injuries than physiological thermal strain; for example, impairment of manual dexterity cannot be prevented with this index.     

The accuracy of estimating the thermal insulation of clothing ensembles - the effect of appraisers

The effect of the appraisers on the estimation of the thermal insulation of clothing ensembles was investigated. Nine appraisers, four experienced and five inexperienced, estimated the total thermal insulation by summing the values for individual garments. Lists of individual garments worn by workers were given during thermal comfort measurements carried out in shops and stores during one winter and summer. The beginners estimated the thermal insulation as accurately as the experienced appraisers. There were, however, great individual differences, for which three main reasons were found. Interpolation between the insulation provided by two garments was insufficient, and the insulation of these garments should be checked in more precise tables. Classification of the garments into heavy, medium and light clothing items was not adequate, and garments not listed by the workers confused the estimation given by different appraisers. The effect of error in thermal insulation on the PMV index is negligible if more than one appraiser estimates the thermal insulation and the mean of the estimates is used.     

Determining temperature ratings for children's cold weather clothing

This study examined the physical and physiological differences between children and adults that affect body heat generation and losses and then developed a heat loss model for determining the temperature ratings of cold weather clothing designed for use by children of various ages. The thermal insulation values of selected jackets were measured using a heated manikin dressed in two base ensembles, and the temperature ratings were calculated using the model. The results indicated that the type of garments used in the base ensemble had a major effect on jacket ensemble insulation and the predicted comfort temperature. For a given level of insulation, the temperature rating decreased as the wearer's age and activity level increased. This is probably because children have a higher surface area per unit mass ratio than adults, and they lose heat faster. However, this effect is partially offset by their higher metabolic rates.     

Design of functional work clothing for meat-cutters

The aim of this study was to design new functional work clothing for meat-cutters, paying particular attention to the metabolic requirements of the work and the thermal and general working conditions in slaughterhouses. On the basis of the results of the pilot study (review of the literature, questionnaires and interviews, work analysis, physiological measurements) different types of work clothing were designed for prolonged used during normal work in meat cutting. Physical material tests and measurements of thermal insulation values (l(cl)), and the follow-up of clothing maintenance were carried out. Further modifications and evaluations of work clothing were based on the opinions of meat-cutters and on the physiological trials in slaughterhouses. The final assembly of work clothing consists of three pieces (cotton/polyester): an apron, trousers with extra insulation in the lower back, and a work coat with extra insulation in the neck and shoulders, and at the wrists. The sleeves are protected against moisture by special textile material. The thermal insulation of this new set of work clothing together with long sleeved and legged underwear is 1.3 clo and it proved to be sufficient for thermal comfort in moderate work in an air temperature of 10 degrees C.     

Effect of physical activity and air velocity on the thermal insulation of clothing

Abstract

Intrinsic thermal clothing insulation and surface air insulation were measured on human subjects by the use of indirect calorimetry. Four male clothing ensembles (0-1-1 -8 clo) and three female clothing ensembles (0-2-1-2 clo) were investigated. Using the standing position as a reference, the influence of sitting, bicycling (40r.p.m., 20 W), walking (3-75 km hour^?1) and of light packing work on the thermal insulation was studied. The influence of an air velocity of 11ms^?1 on thermal insulation during the standing and walking conditions was investigated. The results showed that: (i) intrinsic clothing insulation was maximal in the standing position. It was reduced by 8-18% in the seated position and by 30-50% during bicycling and walking. An air velocity of 11ms^?1 did not influence the intrinsic clothing insulation during walking, but decreased it by 18% in the standing position; (ii) surface air insulation varied with activity and air velocity, but not with clothing. It was increased by up to 25% in the seated position, reduced by 7-26% during bicycling and by 30-50% during walking. An air velocity of 11 ms-1 reduced the surface air insulation by 50% in the standing position and 30% during walking.     

Wearer related performance standards for conditioned clothing

Abstract

Estimates, based on American experience of work in the heat, indicate that in the UK, half a million workers or more may be working in thermally uncomfortable and stressfully hot environments. In addition, many will be experiencing cold working conditions and associated discomfort. The role of protective clothing as one of the factors involved in imposing thermal stress is emphasized.

One method of thermal stress control is to provide conditioned garments which warm or cool the wearer as required. The use of ‘air supplied’ garments for cooling is specifically dealt with and the methods of defining their performance reviewed. The application of the concept of ‘per cent wetted skin surface area’ is discussed as one method of defining the performance of air ventilated garments if thermal comfort cannot be achieved. The use of low pressure air for ventilating garments is proposed. The performance of such a system employing a small battery powered blower is defined in terms of the wearers work rate and supply air temperature and volume using the wetted surface area concept. The necessary steps to be taken by manufacturers if they are to develop the market for such conditioned garments are outlined.     

Effects of condensation in clothing on heat transfer

A condensation theory is presented that enables the calculation of the rate of vapour transfer with its associated effects on temperature and total heat transfer inside a clothing ensemble consisting of underclothing, enclosed air, and outer garment. The model is experimentally tested by three experiments; (1) impermeable garments worn by subjects with and without plastic wrap around the skin, blocking sweat evaporation underneath the clothing; (2) comparison of heat loss in impermeable and semi-permeable garments and the associated discomfort and strain; (3) subjects working in impermeable garments in cool and warm environments at two work rates, until tolerance. The measured heat exchange and temperatures are calculated with satisfying accuracy by the model (mean error = 11, SD = 10 Wm^?2 for heat flows and 0·3 and0·9°C for temperatures, respectively). A numerical analysis shows that for total heat loss the major determinants are vapour permeability of the outer garment, skin vapour concentration and air temperature. In the cold the condensation mechanism may completely compensate for the lack of permeability of the clothing as far as heat dissipation is concerned, but in the heat impermeable clothing is more stressful.     

Effect of posture positions on the evaporative resistance and thermal insulation of clothing

Evaporative resistance and thermal insulation of clothing are important parameters in the design and engineering of thermal environments and functional clothing. Past work on the measurement of evaporative resistance of clothing was, however, limited to the standing posture with or without body motion. Information on the evaporative resistance of clothing when the wearer is in a sedentary or supine posture and how it is related to that when the wearer is in a standing posture is lacking. This paper presents original data on the effect of postures on the evaporative resistance of clothing, thermal insulation and permeability index, based on the measurements under three postures, viz. standing, sedentary and supine, using the sweating fabric manikin-Walter. Regression models are also established to relate the evaporative resistance and thermal insulation of clothing under sedentary and supine postures to those under the standing posture. The study further shows that the apparent evaporated resistances of standing and sedentary postures measured in the non-isothermal condition are much lower than those in the isothermal condition. The apparent evaporative resistances measured using the mass loss method are generally lower than those measured using the heat loss method due to moisture absorption or condensation within clothing. STATEMENT OF RELEVANCE: The thermal insulation and evaporative resistance values of clothing ensembles under different postures are essential data for the ergonomics design of thermal environments (e.g. indoors or a vehicle's interior environment) and functional clothing. They are also necessary for the prediction of thermal comfort or duration of exposure in different environmental conditions.     

Temperature rating prediction of Tibetan robe ensemble based on different wearing ways

Each piece of Western clothing has a unique temperature rating (TR); however, based on different wearing ways, one Tibetan robe ensemble can be used in various environments of the Tibetan plateau. To explain this environmental adaptation, thermal insulations and TR values of Tibetan robe ensembles in three typical wearing ways were measured by manikin testing and wearing trials, respectively. The TR prediction models for Tibetan robe ensembles were built in this research. The results showed that the thermal insulations of Tibetan robe ensembles changed from 0.26 clo to 0.91 clo; the corresponding TRs ranged from 9.90 °C to 16.86 °C because of different wearing ways. Not only the thermal insulation, but also the ways of wearing Tibetan robes was important to determining their TR values. The three TR models and a triangle area for each piece of Tibetan clothing explained its positive adaptation into the environment; this was different from the current TR models for Western clothing.     

The effect of unevenly distributed thermal stimuli on the sensation of warmth and coolness

Combinations of clothing provide different degrees of thermal insulation for various parts of the body. The effect of this uneven thermal insulation on general comfort is examined by using experimental clothing which could provide varying degrees of thermal resistance. The relationship between skin temperature and sensation was found to be approximately linear when the exposed areas were not large, and that clothing of the same thermal resistance can yield different sensations depending on the parts of the body involved.     

The ergonomics of ventilated operating theatre clothing

Abstract

The results of a recent Department of Health and Social Security/Medical Research Council (DHSS/MRC) trial into the use of ultra-clean ventilation systems shows that these can bring about a reduction in the rate of wound sepsis in orthopaedic operations, particularly when body exhaust ventilated clothing is worn by members of the surgical team.

Although considerable information exists about the reduction of bacteria shedding from individuals wearing body exhaust gowns, little information is available about wearer comfort and related problems. This study was carried out to examine the ergonomic consequences for operating theatre staff of wearing ventilated clothing and to compare these with the results for other forms of specialized surgical garments.

The investigation consisted of observations of theatre staff at work, interviews and an experimental simulation of the orthopaedic surgeon's task.

The results showed that there were measurable differences in skin temperature and sweat rate between ventilated and non-ventilated gowns. Subjectively there was a significant preference for certain garments based on general comfort and thermal perceptions. It was concluded that the ’Mandarin’ body exhaust ventilated gown gave high levels of both objectively and subjectively assessed thermal comfort for the wearer. Where there were operational difficulties or objections to using a ventilated gown, it was concluded that a gown made from ’Gore-tex’ was a possible alternative. It is important that the ergonomic and comfort aspects of these gowns should be related to the attenuation in bacterial shedding that they produce.     

Metabolic rate and clothing insulation data of children and adolescents during various school activities

Data on metabolic rates (n = 81) and clothing insulation (n = 96) of school children and adolescents (A, primary school: age 9-10; B, primary school: age 10-11 year; C, junior vocational (technical) education: age 13-16 (lower level); D, same as C but at advanced level; and E, senior vocational (technical) education, advanced level: age 16-18) were collected (Diaferometer, Oxylog, Heart Rate derivation) during theory-, practical- and physical education- lessons. Clothing insulation was calculated from clothing weight, covered body surface area, and the number of clothing layers worn. Clothing insulation was found to be similar to that expected for adults in the same (winter) season, with minimal variation with age or school type (0.9 to 1.0 clo; 1.38 clo where coverall was worn), but more variation within groups (coefficient of variation 6-12%). Metabolic rate values (W.m(-2)) were lower than expected from adult data for similar activities, but are supported by other child data. The results of this study can be used to establish design criteria for school climate control systems or as general data on energy expenditure for children and adolescents. The results emphasize the need for specific child data and show the limited value of size-corrected adult data for use in children.     

Thermal comfort and clothing insulation of resting tent occupants at high altitude

Thirty-nine males and 18 females, in six groups, participated in six high altitude treks (each lasting 3–4 weeks and climbing up to 5500 m) in the Himalaya and Karakoram. Inverse relationships between mean overnight total insulation (sleeping bag plus clothing) and air temperature in tents were recorded for all treks. Average overnight thermal sensations varied little with air temperature as the subjects modified their clothing insulation to maintain thermal sensations warmer than ‘neutral’ for all treks. For combined treks, subjects adjusted their mean overnight total insulation up to 7 clo for thermal sensations of between 0 (‘neutral’) and +1 (‘slightly warm’) on average, measured on the standard seven-point thermal sensation scale developed for everyday low-altitude conditions. Very few subjects (3% of all daily responses, on average) reported ‘cool’ or ‘cold’ sensations. General tent discomfort increased with altitude suggesting that subjects interpreted tent comfort predominantly in terms of thermal outdoor conditions.     

3D quantification of microclimate volume in layered clothing for the prediction of clothing insulation

Garment fit and resultant air volume is a crucial factor in thermal insulation, and yet, it has been difficult to quantify the air volume of clothing microclimate and relate it to the thermal insulation value just using the information on the size of clothing pattern without actual 3D volume measurement in wear condition. As earlier methods for the computation of air volume in clothing microclimate, vacuum over suit and circumference model have been used. However, these methods have inevitable disadvantages in terms of cost or accuracy due to the limitations of measurement equipment. In this paper, the phase-shifting moiré topography was introduced as one of the 3D scanning tools to measure the air volume of clothing microclimate quantitatively. The purpose of this research is to adopt a non-contact image scanning technology, phase-shifting moiré topography, to ascertain relationship between air volume and insulation value of layered clothing systems in wear situations where the 2D fabric creates new conditions in 3D spaces. The insulation of vests over shirts as a layered clothing system was measured with a thermal manikin in the environmental condition of 20 degrees C, 65% RH and air velocity of 0.79 m/s. As the pattern size increased, the insulation of the clothing system was increased. But beyond a certain limit, the insulation started to decrease due to convection and ventilation, which is more apparent when only the vest was worn over the torso of manikin. The relationship between clothing air volume and insulation was difficult to predict with a single vest due to the extreme openings which induced active ventilation. But when the vest was worn over the shirt, the effects of thickness of the fabrics on insulation were less pronounced compared with that of air volume. In conclusion, phase-shifting moiré topography was one of the efficient and accurate ways of quantifying air volume and its distribution across the clothing microclimate. It is also noted that air volume becomes more crucial factor in predicting thermal insulation when clothing is layered.     

Standards for moderate thermal environments

Recently two Draft International Standards dealing with specifications of the conditions for thermal comfort (ISO DIS 7730) and measurement procedures (ISO DIS 7726) have been approved by the International Stadardisation Organisation (ISO). The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) has made a standard with similar requirements for the thermal environment (ASHRAE, 1981). To verify the requirements, measurements of different thermal parameters have to be performed. Guidelines as to how and where to measure are also given in the standards. The present paper deals mainly with the requirements and measurements that are relevant for moderate thermal environments in places of residence, offices, hospitals and light industry. For evaluation of very hot or very cold surroundings, other methods are required. Only measurements of parameters that influence the perception of the thermal surroundings are included.     

A CAD system for multi-style thermal functional design of clothing

Designing clothing with good thermal functional performance is very demanding and time-consuming if we follow traditional design methods. An innovative method consisting of a CAD system, allowing the designer to perform multi-style clothing thermal functional design on a customized virtual human body, is presented in this paper. The new functionalities of the virtual system provide the abilities to perform intelligent design of different clothing styles and materials for different body parts according to individual design requirements, namely design of various categories of clothing, such as hat, coat, trousers, gloves and shoes in the same design scheme. The designed clothing can be worn on a virtual human body and set in various wearing scenarios. The thermal behaviors in the human body-clothing-environment are simulated to predict the thermal performance of clothing and thermal response of the human body at multi-parts. 2D/3D visualization and animation of the simulation results are presented to help the designers to preview and determine whether the thermal performance of clothing is satisfactory and then obtain feedback to improve their designs iteratively.     

Pumping effects on thermal insulation of clothing worn by human subjects

This study was undertaken in order to analyse the importance of the pumping effect on clothing's thermal insulation. To enhance differences in heat exchanges due to the pumping effect, two sets of condition were fixed, minimizing either the convective or the radiative heat transfers. The results showed that: (i) the clothing insulation determined on a manikin, even if he is moving, is larger than the resultant clothing insulation for living subjects; (ii) the insulation is not the same for radiant heat or cold as for convective heat or cold;(iii) the pumping effect can increase or decrease the resultant clothing insulation; (iv) the clothing insulation is smaller in warmer conditions thanin cooler ones; (v) it becomes necessary to make a definite distinction between several kinds of clothing insulation; intrinsic or basic insulation against radiation and convection; effective insulation against radiation and convection taking into account only the heat flowing through the clothing fabric; resultant insulation taking into account the magnitude of the pumping effect when clothing is worn by living subjects     

A quasi-physical model for predicting the thermal insulation and moisture vapour resistance of clothing

Based on the improved understanding of the effects of wind and walking motion on the thermal insulation and moisture vapour resistance of clothing induced by air ventilation in the clothing system, a new model has been derived based on fundamental mechanisms of heat and mass transfer, which include conduction, diffusion, radiation and natural convection, wind penetration and air ventilation. The model predicts thermal insulation of clothing under body movement and windy conditions from the thermal insulation of clothing measured when the person is standing in the still air. The effects of clothing characteristics such as fabric air permeability, garment style, garment fitting and construction have been considered in the model through the key prediction parameters. With the new model, an improved prediction accuracy is achieved with a percentage of fit being as high as 0.96.