Circulating fan vs Exhaust fan

3rd Monkey said:

That's what I'm thinking too. Mine is just a 250cfm in a 4x4x8, but it pulls enough to suck the tent in. Seems like they do better than the air being circulated with another fan.

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WingAK said:

It could also be without a fan the plant spends less time building up the stalks and more time on vertical growth.

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3rd Monkey said:

I've been doing some "testing", or whatever you want to call it, with my fans.

I've run a week with exhaust and circulating fan, and then a week with just exhaust. Did that for 4 weeks total, 2 weeks with each on an alternating schedule.

Here's what I've noticed. With both fans running, growth seems a little slower than with just the exhaust. Just the exhaust seems to grow a little faster. I really thought it would have went the other way.

I've done some mild research to try and figure out why, or if I'm just crazy. The only thing I could find particularly of relevance was the stress by the circulating fan could be slowing growth... Maybe.

Now, I also figured that the stems/stalks would grow larger with the circulating fan, for obvious reasons. I haven't noticed a difference. I do add small amounts of silica.

Just wondering if anyone else has tried it or noticed it. I always believed a circulating fan was necessary, but now I'm not so sure. I haven't tried it on flowering plants, only veg, and different species react the same as well.

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Kingrow1 said:

Ugggh tell me if i reply to too many of your threads as i do talk a lot...

Researched youll find therecare two forms of cooling to a leaf - free cooling and forced cooling. Free cooling happens at below wind speeds of 0.3 to 0.5meters per second (m/s). Above this wind speed we have forced cooling. Free cooling involves convective loss into the environment, the loss of heat through transpiration over the leafs boundary layer through water and radiational cooling also updrafts as the bottom of the leaf is cooler than the surface etc etc etc pretty complex shit.

Wind can carry off heat much quicker so forced cooled leaves loose water fast and have zero boundary layer and find it harder to regulate.

So we see wind is bad but air exchange good as it supports free cooling by removing the heat the leaf decides to loose not have too much heqt ripped from it.

Stems thicken faster with no movement - life and resources work at 100% biological efficiency - stress the stem and efficiency drops because it goes into repair mode which cost resources. A plant will make the most efficient stem thickness and widest stem per plant size in the most optimun conditions.

A note on wind - smell is a lot less without wind and buds moving about. I once had this debate where peeps said weed has to have wind... i simply replied "Do plants drop dead in still air then...?".

Hope that helps, should guide the google a bit better

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3rd Monkey said:

You're always welcome in my threads, no matter what they say about you lol.

Makes total sense to me. That was the conclusion I drew for myself anyway.

Thanks for the info.

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Kingrow1 said:

The air exchange from the exhaust is generally well above what we need for plant cooling and function which is why the fan is uneeded to an extent.

With knowing where to place a thermometer and accurate air temp readings most soon realise they were creating wind tunnels not nice plesant sumner days.

The theory is sound but in practice requires some work - i think i spent to much time on this hobby over the years to even know this stuff, no need to be this technical i think. Everything i do is set to these principles and works fine - the real truth to lowering or raising tent temps is to cool or heat the room its in as fans move air not cool so to say

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