Humidity too high

[CrushnYuba]

reading your thread and your post in this one have been hugely inspirational while i get ready to put up my first greenhouse. here in maine we can have pretty insane humidity. luckily it stays cool enough even through summer that heat is almost always an option. one thing i cant get through my head however is how to pair the heat with intake/exhaust. if you are pulling too much cool and moist air in from outside, wont you defeat all the work the heat is doing for the RH%? I'm guessing its all about using something like half as much CFM coming in as going out? or maybe just run exhaust?

It's about environment controls and properly sized heater. Modern greenhouse controllers know what to do. Even cheap controllers can be made to do it ok. You connect a real small exhaust instead of a dehumidifier to a humidity controller. The thermostat notices the drop in air temp and makes the heat run.
The exhaust i use for dehu is way smaller then one i would use for cooling. Small inline duct fans work well.

 

[Bloom SA]

It's about environment controls and properly sized heater. Modern greenhouse controllers know what to do. Even cheap controllers can be made to do it ok. You connect a real small exhaust instead of a dehumidifier to a humidity controller. The thermostat notices the drop in air temp and makes the heat run.
The exhaust i use for dehu is way smaller then one i would use for cooling. Small inline duct fans work well.

So what you're saying is run a heater and a small exhaust at the same time with no inlet?

I've always read that temperature trumps humidity, and to bring out all the colours and terpenes of the strain, one needs to lower temperature to 17/18 degrees celcius. Does one not loose out on this if they are using heat to lower RH?

 

[914safbmx]

So what you're saying is run a heater and a small exhaust at the same time with no inlet?

I've always read that temperature trumps humidity, and to bring out all the colours and terpenes of the strain, one needs to lower temperature to 17/18 degrees celcius. Does one not loose out on this if they are using heat to lower RH?

well i think thats the one catch to this method, you can only use it if you have about 20 degrees or so to spare. it will work great for me being up north because its always cold enough in late summer and fall. i think around 65-70 is when it would prob be too warm to effectively use heat as a dehumidifer. hey crushnyuba, can you check me on that one? you're the expert. thats just how it makes sense in my head

so i'm thinking for exhausting maybe its best to try and run push out air from a kind of low point in the greenhouse? i imagine as the heat chugs away in there, the hottest and dryest air is gonna sit up high and the cool humid air is gonna hover low. so wouldnt it be best to try and draw the air out from the bottom? also, no intake at all? just a little? from up high? maybe it really doesnt matter haha

 

[CrushnYuba]

Using heat and venting is the greenhouse industry standard. It is only cannabis growers that use dehumidifiers because they are used to indoor solutions.
It definitely works better in certain climates. West coast it works the best. In most climates high rh comes as temp decreases. We measure RELATIVE humidity. Not absolute humidity. We aren't changing how much moisture is in the air. We are changing how much moisture the air can hold.
unfortunately moist air rises as does heat. So I'm not sure how affective low vening would be. You do need an inlet. You heat on the same end as the inlet and exhaust on the opposite side. commercial greenhouses heat and vent in cycles. Even a 10 degree temp bump will lower humidity by 25% over ambient. Plants really grow best in Warmer, more humid environments then most growers run. What do you consider ideal? You would be surprised what a little higher heat and humidity can do for your yield.

 

[wiadro]

I have a cold snap early in the growth, but it's good that the quality seeds saved the situation. Bought by the way on https://konopinasiona.pl/

 

[redlaser]

I am learning so much from this thread. Thanks Redlaser for the info.

What is the size of your greenhouse ?

What heater are you using ?

Do you have an idea of monthly fuel cost?

I am only planing on a summer grow looking for small plant count larger weight/plant.

Better late than never in answering this I guess.

I don’t have an idea of monthly heat cost.

This building is not a traditional greenhouse , it has metal sides to it. It lacks insulation to run it year round at this point. I’ve ran the heat for several weeks at a time in the fall to finish some plants, flies through propane. Once it’s insulated it should be a lot easier maintaining humidity control at night.

Heaters are Lennox