Photosynthetically Active Radiation (PAR) Analysis

Hi all,

I’m looking for any suggestions about PAR analysis by ladybug tools. I have checked there was a similar topic last year. Here It seems there was no conclusion. I have also read lots of articles about conversion between solar radiation (w/m2) and PAR.

I’m wondering if there is anyone got experience in setting this kind of tool for PAR analysis. Any comments are appreciated.



Hi Josh,

We have encountered this a number of times in glasshouse designs and often there are different targets from the botanist, sometimes it is hours over a certain brightness, as could be calculated out of an annual illuminance simulation, or as a fraction of outdoor light availability, which may be as simple as a daylight factor calculation. If the botanist is happy with illuminance as a proxy for PAR, that can be worthwhile for designing around performance of low-light spaces that may not receive direct sun.

We generally let the Botanist calculate PAR via a preferred conversion method from that illuminance value (perhaps it is from local measurements), though I appreciate this does not take into account material reflectance of the non-visible PAR wavelengths (keeping it simple).

The language in agribusiness and plant conservatories is generally a daily light integral, which is simply the cumulative illuminance over a day, measured in lux-hours. This at least is a simple bit of post-processing out of an hourly simulation and can be built into a grasshopper workflow without much hassle.