Psychrometric Charts

Posted by hsiehy3 on April 12, 2011 · Leave a Comment 

In the filed of architecture, it is essential to understand the climate of the site to equip the building with the right mechanics. A Psychrometric Chart is often used for climate analysis. On one graph it shows six different aspects to look at the weather condition: dry bulb temperature, wet bulb temperature, relative humidity, dew point, humidity ratio, and time period.

To draw a Psychrometric Chart, one must have at least two sets of data about the weather aspects,
Also, one must have one set of high and one set of low number of data (usually the max and min) for each weather aspect, This allows to create two points for one period of time (usually one month) and by linking the two points, one create a line of conditions within the period of time.

Mapping out the dots of information is the most complicated part and must be done carefully.
It is easy to read the wrong number from horizontal bands of data.

In the data sets above,
HIGH relative humidity occurs at LOW (normal) temperature (at approximately 4:00 am),
while LOW relative humidity occurs at HIGH (normal temperature (at approximately 4:00 pm or 16:00).
It is easy to misplace the dots on the graph and crate a very different geometry on the chart.

Here is the Psychrometric Chart of Honolulu that I created using the dry bulb temperature and relative humidity.

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