# Can humidity levels be too high?



## silence882 (May 29, 2020)

Hi all,

Turns out my new orchid cabinet is working better than anticipated at keeping humidity levels up. They're staying at 90-95% throughout the day and night. I never thought as an indoor grower I'd have to ask this, but is my humidity too high? I've got a wide range of Paphs and Phrags in my cabinet, so unfortunately I have to determine what single conditions are best for the widest variety of slippers.

Thanks!
--Stephen


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## Ozpaph (May 29, 2020)

I think if its really high all the time fungal problems might be more prevalent. But thats anecdotal.


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## tomkalina (May 29, 2020)

Can you install a small exhaust fan in the cabinet?


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## MaxC (May 29, 2020)

That high you might have issues with condensation and water pooling in your cabinet. We have had a really humid few days and my humidifiers were running at full blast push my rh to 90%+ and was causing water to build up in spots. If you get that water pooling in crowns it could get out of hand.


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## silence882 (May 29, 2020)

Hmm so what would ideal humidity be? 80%?

Yes, I can add vent fans. I just bought a pair along with a humidity sensor switch from Amazon. I just need to know what humidity range is ideal...


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## Ray (May 30, 2020)

To me, “ideal” is that point where the humidity is just low enough that condensation doesn’t occur. You can use a dew point calculator to see where that is.


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## NYEric (May 30, 2020)

Too high, yes, ever heard of crown rot?


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## tomkalina (May 30, 2020)

Yes, but not from high humidity. It's not unusual for our high humidity alarm to go off because the sensor reads 98% humidity; usually early in the morning. When I walk through the greenhouse early it is not unusual to see small water droplets on the edges of leaves that have formed because of condensation. Totally acceptable with our growing conditions. The reason why we don't have crown rot is because we combine that humidity with vigorous air movement and the condensation never gets to the point where the crowns are loaded with water.


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## Ozpaph (May 30, 2020)

I would assume humidity varies during the 24hrs. Maybe look up that data for the 'commonest' plants in your box.


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## silence882 (May 30, 2020)

Ray said:


> To me, “ideal” is that point where the humidity is just low enough that condensation doesn’t occur. You can use a dew point calculator to see where that is.


Thanks! I'll compare this against my temp readings and see what I get.



NYEric said:


> Too high, yes, ever heard of crown rot?


No, what's that?



tomkalina said:


> Yes, but not from high humidity. It's not unusual for our high humidity alarm to go off because the sensor reads 98% humidity; usually early in the morning. When I walk through the greenhouse early it is not unusual to see small water droplets on the edges of leaves that have formed because of condensation. Totally acceptable with our growing conditions. The reason why we don't have crown rot is because we combine that humidity with vigorous air movement and the condensation never gets to the point where the crowns are loaded with water.


Unfortunately, I can't get very high air movement in my cabinet without turning it into a mini tornado. I think I'll err on the side of a bit lower than possible.



Ozpaph said:


> I would assume humidity varies during the 24hrs. Maybe look up that data for the 'commonest' plants in your box.


Luckily, I've got a WiFi thermometer/hygrometer in the cabinet. I'll use it to pick a humidity level.


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## xiphius (Jun 1, 2020)

Agreed with Tom. No such thing as too high humidity, just not enough airflow . If you have 100% humidity in a completely stagnant environment, then all of your plants are going to rot (probably). If you have 100% humidity in a place where you have exceptionally good airflow, then you probably won't have too many issues. That said, definitely keep a close eye. If a rot problem does crop up, it will progress much faster in higher humidity conditions...

If you are growing in a cabinet, CPU fans can do wonders for creating a nice airflow without a "tornado" effect.You can also hook those up to speed controllers so you can tune the airflow to your desired level.


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## MaxC (Jun 1, 2020)

I second the CPU fans, I got a few AC Infinity fans, as they are not too expensive. I have one dedicated to provide low constant air (7/6.5 watt) for a couple of plants that need it and a more powerful one that gets a whole rack flowing (22/18 watt), though that one is a little loud and sounds like someone is vacuuming. As well as getting a speed control you can daisy chain them if you need to.


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## richgarrison (Jun 2, 2020)

riffing on the comments already above, air flow without fresh air, is swirling the toilet.... What seems to always be missing in the conversation is that fresh air is important.... @tomkalina has fresh air inlets in his greenhouse. Sam will tell you about the need for fresh air exchanges in the winter. Sue Bottom writes at this link about the need for fresh air. 

in your closed environment that will be an interesting design problem, but one that must have solutions given all the folks that have built similar setups.


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## troy (Jun 2, 2020)

60-70% humidity all the time is perfect with a jet stream of fresh air!!!


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## silence882 (Jun 3, 2020)

Hi all,

I installed two exhaust fans in the cabinet hooked up to a humidity controller. Right now it's set to 70% +/- 5%. I'll see how that does for a while.

I did get AC infinity fans. I've been using a pair of them inside the cabinet since I built it last fall and they've worked great. I am pretty surprised at just how fast these two fans can reduce the humidity level inside the cabinet. I'll post a screenshot from my logging hygrometer in a few days to demonstrate how it's working.

Here's the new setup:






Each fan exhausts from one of the two shelves. The doors and side panels are leaky enough that the exhaust fans can pull air in through the gaps without a problem. I guess if I have to, I can flip one fan around to have a flow through the cabinet. But I don't think it will come to that.

--Stephen


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## MaxC (Jun 3, 2020)

What wattage of fan did you go for?


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## silence882 (Jun 3, 2020)

MaxC said:


> What wattage of fan did you go for?


8 watts. This one:
https://www.amazon.com/dp/B009OWVUJ0/ref=cm_sw_r_other_apa_i_rZg2EbHQDZ49A

I need something quiet since the cabinet is in the dining room.


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## gego (Jun 4, 2020)

My take on this, when in closed environment, the water from plants leaves, potting and everywhere inside will evaporate (fan and high temp) and reaches saturation if there is no exchange of air that will absorb that moisture. This environment becomes really bad when the temp goes down in the night time or when your lights turn off. Saturated air will not stop transpiration on the leaves as it could no longer absorb any moisture . So the roots will not have the force to take up water and nutrients from the media/potting. 
So an exchange of air is needed. If you have a closed environment like mine inside a room or in my case in our basement, you probably don't want that moisture create some mold problems in your house.
In my case, I simulated the exchange of moisture inside my closed orchid house by using a de-humidifier. The circulated air by fans will pick up moisture. When the the moisture hits the limit you set on the de- humidifier, it will then take that moisture and drain to a container. That water is distilled water so you can reuse that again. The setting is usually +/- 5% of your desired humidity. In my basement, I use the lights to increase my day temp, but not enough to get to a 10 delta, the exhaust of the de- humidifier is warm air and will help increase the temp.
If you have enough plants, the water from the potting and basin to catch the water will provide the humidity, it is now the job of the de-humidifier to create a healthy exchange of moisture. In a closed system, humidifier is useless.


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## gego (Jun 4, 2020)

Correction: "saturated air will stop transpiration"


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## jht.orchids (Jun 6, 2020)

Read up on Vapour Pressure Deficit (VPD) - I'm sure you'll realise that 100% RH is a no-no.


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## silence882 (Jun 7, 2020)

I am convinced to keep humidity well below 100% and to keep up good air flow! So far it's working:


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## Ozpaph (Jun 10, 2020)

That's an interesting video that reinforces commonsense - hot and dry is bad, as is cold and wet.


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## Ozpaph (Jun 10, 2020)

You dont seem to have much diurnal humidity variation - I presume because its a totally artificial/controlled environment


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## silence882 (Jun 10, 2020)

Ozpaph said:


> You dont seem to have much diurnal humidity variation - I presume because its a totally artificial/controlled environment


Yes, because the humidity in the cabinet in the summer will stay above 85% all the time, reducing it with fans to 70% means there will be no diurnal variation. I supposed I could see if there is a more advanced controller for the fans that incorporates a timer. But I don't think I'm at that point yet as the plants seem happy.


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