that kinda stff is what i need to learn i read ppl talking about just what you said above and to me its like alien talk, intakes out takes vent flaps air exchange possitive negative air pressure <<all that stuff means nothing to me......
Intakes are the fans that are bringing fresh air into the grow space.
Out takes would be the fans that are exhausting/venting out the air from the grow space.
Air exchange is simply the process of changing out the air in your space...out with the old in with the new. Example: if you have a space that is 10x10x10...that would give you 1000 cubic feet of space/air in your grow. If your using a 440CFM(cubic feet per minute) then it would roughly take you 2+ minutes to completely change out the air if there are no restrictions.
Positive pressure is when you have more intake air than out take air...causing a build up of pressure in the space.
Negative pressure is what your experiencing. Its when you have more out take/exhaust then you have intake air coming in...causing your tent walls to cave in
im very simple in wah i do over here i just know when i zip my tents up ALL 4 SIDES suck in about a foot which crushs all my plants on one side of the perimeter pots...
^that would be negative pressure causing the tent to suck in like that.
ive recently twisty tied some boards on the inside of my tents that helps alot and keeps the tent from crushing my plants......
i have one 6inch fan its a can fan and i believe its the 440 cfm and i have it ontop of my tents where i have a sheet of light ply board where i have my ballasts aswell, now i have a scrubber in each tent and there BOTH hooked to the one fan which i thought would help with the NEG pressure in the tents and keep the sides from being sucked in but hell no it dont anything of the sort...
for now the boards i put in place will work untill something better comes along...i was told about some type of device that you could use to control the speed of the fan but like i said that kinda stff is not something im good with/at.
peace;)