Adjusting the padding around the chart.Īdded a checkbox in the PROCESS LINES panel to toggle the position indicator on and off. In addition to the bioclimatic chart, you can also overlay the Heat Index, Predicted Mean Vote (PMV), ASHRAE Standard 55 comfort classes and EN-15251 comfort categories, as shown in Figure 8.įigure 10f. However as one of my aims with this tool is to highlight the differences between using relative and absolute humidity, I would argue that it is a widely used term that, as long as the units being used to measure it are clearly displayed, is sufficiently well understood to warrant its use as a lexical counterpoint to relative humidity. I understand that humidity ratio is probably a more technically correct definition as some argue that absolute humidity is too general as it could potentially be used to cover a range of measures, humidity ratio and vapour pressure included as they are both absolute measures of humidity. Absolute Humidity vs Humidity RatioĪt this point it is probably worth noting the issues associated with using the term absolute humidity to describe the vertical axis. The hope was that by simply animating back and forth between the two chart types, most of that explanation would become pretty obvious as you get to see clearly almost all of the psychrometric processes change from straight lines under the absolute humidity axis to complex curvilinear lines under relative humidity.Ī by-product of this transition is that bioclimatic regions, when viewed against relative humidity, become a reasonably recognisable 90° rotated version of the original Olgyay bioclimatic chart, which helps in understanding the contribution of Givoni and Milne. Thus, one of the reasons for developing this tool was to see if I could morph seamlessly between the standard psychrometric chart and the much simpler relative humidity chart. Having previously taught psychrometrics to architects, I always found it challenging to convincingly explain why the psychrometric chart used humidity ratio or absolute humidity in the vertical axis instead of the more familiar metric of relative humidity, and why it was so important to understand the various metric lines.
Figure 7b: This can also be done in the relative humidity chart and mapping the same data.
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