How is the "comfort or not" determined in the PMV comfort calculator component?

May I ask how is the “comfort or not” is determined in the PMV comfort calculator component?

The annual percentage of comfort hours doesn’t seem to correspond to the percentage of hours of which the PMV is between the acceptable range from -0.5 to +0.5

Appreciate your kind advice!

  • Ji


The PMV function contains a threshold PPD which it uses to decide whether a given set of conditions are comfortable or not. The conditions are comfortable when the PPD is below the comfort threshold while they are uncomfortable above the threshold. The default threshold is 10% PPD, which is the threshold recommended by ASHRAE and the ISO for the majority of buildings. However, for less-occupied spaces like corridors, these organizations recommend a 20% PPD threshold. Also the ISO recommends a (somewhat crazy) threshold of 6% for spaces like operating rooms of hospitals. You can change the threshold used by the component using the “Ladybug_PMV Parameters Component” like so:

I should also state that the 10% default threshold corresponds with the PMV range of -0.5 to +0.5, although it should be noted that -0.5 and +0.5 are a ever-so-slightly larger than 10% PPD according to how the model is defined (I think it’s about 10.1% PPD). What has made you think that these two do not correspond? Is it just this small difference or something else?


How to use PPD Comfort (386 KB)