Humidity for orchids....maybe too high?
 

I purchased a glass Ikea unit to make into a greenhouse of sorts for my orchids. The temperature is a few degrees higher than in my apartment which I am sure the orchids are happy about. Now it's running about 73 degrees day time and 68 night time. My question is about humidity. I have a variety of orchids in this cabinet greenhouse....oncidiums, cattleyas, doritis, maxillaria, dendrobiums..... I have a fan in there that runs 24/7 for air circulation and I try to open it up for about 20 minutes a day to allow for some new air in the cabinet. How much humidity is too high? With the plants dry today it was like 77%. I watered them and it shot up to between 91-96%. I expected some type of up tick, but wow. I also don't want to do my plants a disservice. I have a tray with some lecha in it with water which I can remove, but I also put weather stripping on the door to help with temp and humidity. Any suggestions and advice? Thank you!!!!

In my opinion, high humidity with constant air movement is great. It’s when it gets stagnant or condenses into the plants that the high RH is an issue.

My greenhouse in PA rarely got below 80% and was in the 90’s most of the time.

Logic transferred from greenhouses used for terrestrial plants suggests that’s too high, because the low “vapor pressure deficit” (VPD) slows transpiration, slowing growth, but it appears that orchids have somehow managed to avoid that issue.

I have considered adding another fan to the top since the fan is in the bottom and facing up because I don't feel a ton of airflow. I watered my plants yesterday and the humidity was up to 96% but no condensation seen on the windows or on the plant leaves. I am hoping to get temp up a little more because I think they would be a little happier thay way.

You don't need a "ton of airflow", you just need gentle, tumbling air so there are no stagnant pockets.

Maybe I can stick something to the top just to make sure air is moving up top...