# Alternative Method for Predicting Thermal Response in Two-Layer Systems
## 4 Discussion  
At 0.25 m/s, the effect of the spacer design had a stronger influence on the insulation than the material itself (Figure 2). The closed-spacer design demonstrated an increase in insulation to about 50% for all the samples, while the open-spacer design demonstrated an initial increase in insulation to about 35% at the 5 mm microclimate thickness and then a decrease. The values at the 25 mm microclimate thickness were similar to the starting value at 0 mm. Similar observations are seen in Figure 3, but at the 10 and 25 mm microclimate thicknesses, there was a larger difference in the samples, especially D, which demonstrated a larger decrease in insulation than either of the other materials. The overall trends of increasing insulation in the closed spacer and the increase-decrease pattern in the open spacer remained the same. At the 1.3 m/s wind speed, Figure 4 demonstrates a much larger difference in the samples in the closed-spacer design. Samples B and C showed 2* the insulation values at the 0 mm air layer, while sample D peaked at 1.6* the starting value. Similarly, with the open-spacer design, sample D demonstrated a much lower increase in insulation compared to samples B and C.  
Overall, this showed that the environmental conditions, wind speed, ventilation, and microclimate thickness had strong effects on the insulation. At the 0.25 m/s wind speed, the ventilation and microclimate thickness had the strongest effects. But as the wind speed increased, the material construction began to have more of an influence. In some cases, such as sample D at 1.3 m/s, the material construction mitigated the effect of the environment, and the open-spacer design saw minimal differences in insulation as the microclimate thickness increased. The largest influence observed was at the 25 mm microclimate thickness, which yielded an insulation increase of 8% for sample D. While these graphs were helpful in the observation of the interaction of the materials with the environment, the trends are relative to the starting point, the 0 mm microclimate thickness. Therefore, calculating the heat balance and sweating rate using absolute R\({}_{\text{ct,tot}}\) values gave a more applicable comparison. Figures 5-7 show that a low metabolic rate could be compensated for solely through dry heat loss for all the samples at the 0 mm microclimate thickness, but this was heavily dependent on the wind speed and level of ventilation. The presence of an air layer increases the insulation of the system, but at wind speeds above 0.5 m/s and with ventilation present, the material insulation can be negligible. With a microclimate of at least 5 mm in the closed-spacer design, every sample needed some level of sweating to compensate for the metabolic rate. However, in the open design, sample D was able to compensate for the metabolic rate solely through dry heat loss at 0.5 m/s and a microclimate thickness of at least 10 mm. At 25 mm and 0.5 m/s, all the samples were able to compensate for the metabolic rate solely through dry heat loss, further showing the importance of the environmental parameters. Figure 8 demonstrates that, at a higher metabolic rate and a low wind speed of 0.25 m/s, the material did not have much influence on the sweat rate, except at the 25 mm microclimate thickness, where the open-spacer design showed lower sweat rates than the closed-spacer design: approximately 385 g/h/m\({}^{2}\) and 450 g/h/m\({}^{2}\) for all the samples in the open vs. closed designs, respectively. Figure 9 showed a similar result, with the open-spacer sweat rates being almost half the closed-spacer sweat rates at the 25 mm microclimate thickness: around 420 g/h/m\({}^{2}\) vs. 230 g/h/m\({}^{2}\) for the closed and open designs, respectively. A similar pattern was observed at 10 mm. Figure 10 demonstrated similar overall trends but also a larger difference between the materials. This implies that the material construction had a more prominent effect as the wind speed increased.