Air..

Hi, just a curiosity that might reduce the spending a little..

What happens if I only have intake fans (2x 16cm 33w), 3 fans circulating the air inside but no exhaust? I mean, only intake, no exhaust..
Or intake fans and only a few light proof holes on top so that heat dissipates through there?

Any idea welcome..thanks!

You're going to have some odor issues come flowering...

that's no issue for me...i mean, will it stress the fans?

You would be better served having exhaust fans and no intakes.

This way air is passively drawn into the area.

J

yes, much better control having fans for exhaust and not intake. reverse it.

plus plants like fresh air.

no, plants make fresh air, they dont need it.

Ok, I'm going with the passive intake, active exhaust. Thing is: My growroom is a wardrobe that I built, and it's back is 2 cm off the wall!
I have two really good fans on exhaust 8inches..
Regarding light issues, I think I can stick a black thick paper on the inside of the holes so that when air ceases to flow, the "lid" falls down..This any good?

My main concern is,
if I make 6 x 10cm on the very bottom on the back side, will it be enough for good air ventilation having the wall 2cm apart?

Thanks 4 quick replies..I'm waiting for your input to start modifying asap.

Stick with a 2-3 to 1 ratio on the intakes, if you have 2 - 8" fans exhausting and only 6 - 10cm intake holes you will be grossly negative( the door the room won't open), you need at least double that if not more or it will be hard on every thing.

Remember an 8" fan pulling 5to600+cfm will need passive intakes that can breath that much air at the same time. So at least 16" to 24" of intake openings to accomodate the "pull" of the fan, you have double that, so 32" to 48" of total intake openings to keep from "starving" the exhaust fans for air. If you go too negative, you won't be able to open the door to the room without throwing your back out..lol

I do not know the total size of the area, but 2 - 8" fans will do a fairly large room, looks like way to much exhaust for the area served...jmo

Peace

Asmallvoice

Passive intakes need one or more holes that equal FOUR TIMES GREATER than your exhaust in order to create negative pressure... So take that into account when you don't have an active intake. I tried to do this with my box and just ended up with a box full of holes and the temp dropping only 2 degrees and hardly any circulation even with circ fans in there.
So I had to plug all the holes up, and once I added an ACTIVE intake it dropped 10 degrees and plenty of circulation.
Passive intakes are useless unless you have a powerful exhaust

SnakeByte said:

Passive intakes need one or more holes that equal FOUR TIMES GREATER than your exhaust in order to create negative pressure... So take that into account when you don't have an active intake. I tried to do this with my box and just ended up with a box full of holes and the temp dropping only 2 degrees and hardly any circulation even with circ fans in there.
So I had to plug all the holes up, and once I added an ACTIVE intake it dropped 10 degrees and plenty of circulation.
Passive intakes are useless unless you have a powerful exhaust

Click to expand...

okay, here we go

negative pressure is the result of more air going out of the space than is coming into the space, which is achieved just by putting an exhaust with no intake = maximum negative pressure
the moment you start adding intake holes, the negative pressure begins its journey towards being neutral( meaning what comes in matches what goes out, in other words, balanced)

This is a law of physics that will not budge, period. You can find balance in the system by using a piece of paper to "gauge" the amount of "pull" at the intake, if the paper is trying to get sucked out of your grip, you need more intake, when you find the " balance", the paper will just barely pull in or rock back and forth in the opening, this is a neutral system. you can then add a bit more negative( pulling more into the intakes) by reducing the intake a little at a time, till you find a happy medium you can live with.

Try to always exhaust from the top and intake from the bottom to improve overall air flow in the space. Air is as lazy as water and will stratify and you can end up with "stale" spots in the area, hince the need for a good circualtion fan in the space, serves multiple functions.

It's not rocket science, but it is ridgid in its ways and there is no way to cheat it.

Hope this clears things up abit

Peace and Great Grows

Asmallvoice

Thanks..!!