Question about air exchange rate

[vacuumlungs]

So I have a greenhouse that’s 20X45ft and 10ft high at the top with 4ft side walls that roll up. I’m trying the figure out what kind of fan I’m going to need. How often do I need to exchange the air? I’m seeing an average recommendation of every minute. Anyone else want to weigh in on this?

 

[I'mback]

The avg is 25-30 exchanges per hour, right up to 60

 

[Snook]

Pictures? Please put some up. I'd like to see it.
EDIT: I'm jealous.

 

[troutman]

Having a window or vent at each end of the greenhouse will help venting.

 

[vacuumlungs]

The avg is 25-30 exchanges per hour, right up to 60

Everything I’ve been reading says that you need to be able to exchange the air in a minute. In other words, my greenhouse is roughly 8,000 cubic feet, therefore I would need 8,000 cfms of ventilation. You’re saying I could get away with as little as 2,000? There’s not a lot of clear info out there and I’d rather not rely on listening to the guy who’s selling it to me.

 

[smokinfat024]

My neighbor doesn’t exchange any air at all in his 25x80. It feels pretty humid an muggy in his gh. He has fans an just doesn’t use them an he also leaves his gh covered throughout the night. I’ve seen it get 120 degrees in there. He only has roll up sides on one side.

 

[smokinfat024]

I’m sure it affects his growth and yield tho

 

[vacuumlungs]

My neighbor doesn’t exchange any air at all in his 25x80. It feels pretty humid an muggy in his gh. He has fans an just doesn’t use them an he also leaves his gh covered throughout the night. I’ve seen it get 120 degrees in there. He only has roll up sides on one side.

Those aren’t the kind of conditions I’m shooting for.

 

[smokinfat024]

I hear ya it blows me away how good the plants look when it’s 120 in there. I’m also shooting for better conditions haha. Can’t wait to do some dep next year. Still gotta build a gh next March.

 

[Self Sufficient]

A good air exchange rate would be anywhere from once every 5 minutes to 5 times every minute. Shoot for between there.

 

[vacuumlungs]

A good air exchange rate would be anywhere from once every 5 minutes to 5 times every minute. Shoot for between there.

That’s pretty broad.

 

[Self Sufficient]

That’s pretty broad.

Exactly. It's not an exact science and it depends on your exact conditions at a particular time as to what is best. It will usually fall within that broad range.

If your co2 ppms are consistently above 600 and your temp and humidity are good, you will need less air exchange than if you're co2 ppms are dropping below 500 and your temp is too hot or too humid.