Modern clothing systems are continually making participation in outdoor activities more accessible, comfortable and safe. There has been considerable innovation in the engineering of clothing worn next to the skin and of outerwear designed to provide protection from foul weather. In this investigation, a novel application of highly permeable spacer fabrics has been studied, by incorporating spacer fabrics as insulating components in clothing systems. A preliminary investigation of the effects of a foam·based spacer fabric on human comfort indicated that the thermal resistance and moisture vapour permeability of such a material are highly dependent on air flow present in the clothing, and can offer some improvement in thermo physiological comfort over conventional insulation. Subsequently, a range of fleece and spacer fabrics were selected and characterised, using a variety of laboratory techniques to elucidate the effect of air flow on the thermal resistance and water vapour permeability of mid-layer fabrics with different structures. It was found that due to their high permeability, the thermal resistance and water vapour permeability of spacer fabrics was more significantly affected by changes in air flow over and in the structure of the fabric than conventional fleece fabrics. One spacer fabric and one fleece fabric were then selected from this range and made into bespoke garments. Using a thermal manikin, the thermal resistance of the garments and the additional heat transfer available through garment openings was measured. Spacer fabrics were found to improve the heat transfer capabilities of the garment openings. In order to evaluate the effect of the spacer fabrics on the thermal properties of clothing systems, the garments were assessed in wearer and field trials using both objective and subjective measures. Provided the exercise intensity was suitably high, the spacer fabric provided improved comfort, as evidenced by lower next-to-skin temperature and humidity recorded in the clothing. A suggestion for the future design of clothing based on the conclusions of this research is that for the widespread adoption of spacer fabric insulation to be plausible, design innovations that limit undesirable heat loss due to ventilation should be developed, and improvements to the sensorial properties of spacer fabrics should be made.

Personal cooling garnents (peGs) are designed to relieve thermal stress in occupations that require the use of personal protective clothing (e.g. fire fighter, military personnel). The cooling source in peGs is usually delivered continuously, which over long periods requires a large battery source. Intermittent cooling has been found to be as effective as continuous cooling at maintaining thermal balance. Based on the observation that larger improvements in thermal perceptions are associated with rapid changes in skin temperature, it was hypothesised that intermittent cooling could also enhance thennal perceptions (i.e. temperature sensation and thennal comfort). The overall aim of the studies presented in this thesis was to test this hypothesis. In order to detect differences between intermittent and continuous cooling on thermal perceptions, it was important to use a reliable measurement tool to assess perceptual responses in conditions where a PCG would be utilised. The first study described in this thesis assessed the reliability of a graphic visual analogue scale (VAS) against a Likert scale (LS) for validity and reproducibility in the measurement of thennal perceptions in non-uniform, dynamic thermal environments. The study involved three identical conditions in which thermal perceptions were measured by both the V AS and LS in response to changes in the torso microclimate. During the condition, participants walked (Skm.hr-] , 2% incline) in a warm environment (3S0C, SO% relative humidity [RH]) and wore clothing (I.2 clo) that covered 88% of the body. The torso microclimate was manipulated by ventilating air of different temperatures and relative humidity through an air-perfused vest (APV). These thermal conditions were similar across all the studies presented in this thesis. The V AS were found to be slightly more reproducible for local thermal perceptions than the LS , and had greater validity during both stable and non-uniform, dynamic thermal environments. Therefore the use of the graphic VAS was adopted in all subsequent studies. To develop the intermittent cooling profiles that were assessed for their ability to enhance thermal perceptions, the second study involved ventilating different air temperatures (-15- 26°C) through the APV to determine what type of flu ctuations in skin temperatures are required to enhance thermal perceptions. The results suggested that the rate of change in mean skin temperature (f'sk) and torso skin temperatures (T sktorso) had a greater influence on thermal perceptions than absolute changes in Tsk and T sktorso. The results also confirmed the results from the first study, that increasing evaporative heat loss at the skin surface was the most effective method to manipulate the rate of change of skin temperatures, and consequently, thermal perceptions. To compare the capability of intermittent and continuous cooling profiles to enhance thermal perceptions, whilst maintaining thermal balance, the final study involved ventilating the APV with either fluctuating or continuous air velocities during both exercise and rest Three different intermittent cooling profiles were used; sinusoidal, sawtooth and step-change. Upon completion of the experiment, participants stated their preferred cooling profile. Based on the results it was concluded that intermittent cooling, which had 50% less air flow than continuous, maintained both thermal balance and thennal comfort when compared to continuous cooling. Out of the intennittent cooling profiles, the sinusoidal profile produced significantly cooler sensations and was 4111 participants' preferred choice. The results suggest that the presence of a significantly higher torso relative humidity (RH1orso) in the intennittent cooling profiles, compared to continuous profile, may have confounded their capability to enhance thennal perceptions over time. In addition, the cooling profi le that was perceived to the 'coolest' and/or the most ' stable' was generally the participants' preferred choice. This suggests that large fluctuations in skin temperature are not always perceived favourably. Based on the studies conducted as part of this thesis, it is concluded that in order to minimise high levels of RHtorso and provide smoother transitions in temperature sensation, an optimal cooling profile should consist of: 1) a sinusoidal pattern with a frequency greater tban 0.000139 Hz, 2) have a ratio of 2:1 ON/OFF periods, 3) OFF periods no longer tban 3 minutes, 4) highest flow rate not to exceed 255 L.min-], 5) provide a rate of change in f sk and t sklOISO of -{).29°C.min-1 and O. 78°C.min-], respectively, and 6) the incorporation of a drying agent into the design of an APV.