Venting For Dummys volume 1

[dnotrem]

Hey guys I was horrified about venting before I leaned this and it brought everything into perspective for me. I am a new grower but I love to learn and when I find good info I want to spred it around. It may not be 100% exact like I said I dont know everything but Anything to help is better then nothing if anyone sees any thing wrong feel free to correct me Im human. Just dont be a dick Thanks







A FEW TIPS I LEARNED THAT MADE VENTING A BREEZE

(Exhaust) CFM volume what will be required for you room
A 10 wide X 10' long X 10' high has 1000 cubic feet of volume (10x10x10=1000). So, a 200 cfm (cubic feet per minute of air flow) exhaust fan is required at Minimum (1000 cu ft divided X 5 min = 200 cfm). Now this is just an example to show what CFM is required to empty that space within a 5 min period with no heat !!! these are the other variables to that must be factored in this was just a basic simple example
(1000/5=200)

(Exhaust) CFM’s will be needed for your room
Growers often multiply their square footage by eight too compensate light heat electrical heat……to determine fan capacity for cooling. These are a requirement for optimal growing conditions. For example, a 10' wide X 10' long grow room would require 800 cfm fan capacity(10 X 10 = 100) (100 X 8 = 800).


(Intake) requirements
To determine your intake requirements really the easiest way is too subtract 25% of you exhaust CFM’s and you will be ok with in/out. Now we have the in/out figured out as a rule of thumb one square foot of opening to the area is required for every 700 cfm of exhaust output. So to make this a bit easier if your exhaust is 700 CFM’s too ensure even flow you would need about 5- 2” holes
Otherwise static pressure (the room sucking into itself), will severely limit the exhaust output. So you need all you openings/holes ect… in one area to equal flow. Intake and exhaust must be exact but the air must move threw the enclose just as easy the only way I can put it is if you had a straw 4” round on each end but was only 2” in the middle you only going to get what the 2” middle allows. These are just some tips I found for figuring this out. This is always is looked at as kind of complicated but when you break it down its not to bad just trying to remove the stigma from venting for the average Joe hope it helps Thanks

 

[guest 77721]

I've got some handy charts for sizing ventilation.

This one is for calculating your overall ventilation rates


This one is for calculating airflow for heat removal


This one is for intake sizing


Pop by one of my ventilation threads or the Lodge if you need help with a growbox design or if you're having ventilation problems. There's always a cold beer in the fridge at the Lodge.

 

[dnotrem]

LOL Wow I wish I had seen this 2 days ago before I did a ton of research then calculated it out the old school way then wrote a page on it oh well I learned a lot about air flow and venting from it. But yea I just started a new cab today I think I nailed the design it just im trying to save money but taking a blower motor from one of the old heaters we have but here it is if you wanna take a look Thanks

 

[dnotrem]

Im trying to make the fresh air come up from the floor with a bunch of 1" Pvc drilled into it that way the plant get an even air flow all the way around.It sounds good in my head but yea tell me what you think

 

[guest 77721]

Oooh lot's of chambers, maybe too many. The NGB design is a seductive bitch and was never a well proven design.

Multiple chambers means lot's of points to lose airflow to static pressure losses. The rule of 2x intakes to exhaust sizes comes into play. The last chamber has to have an intake of 2x the exhaust of the one preceeding it. If you're going to have three chambers in a row then the size of the intakes gets silly like 8x the final exhaust size.

The best thing you can do is build her up and let her run for a few hours. Get a good thermometer and take temp readings of ambient, shaded grow box and exhaust. I have good directions in my Ventilation testing thread for calculating the effective CFMs.

 

[dnotrem]

Thats was also one of the things I was worried about so instead of a bunch of 1" PVC maybe 4 2" peaces that still splits the air even but I am worried about static pressure losses I keep using the duct reduction in my cab cus we use it at work all the time but then I remember its just for long spans so what would you sugest one exit rout for each chamber I dont like just a PVC elbow it just dont seam like it's the best way yea the easiest. I just like to think outside the box ALSO I wanna take the blower motor from an old gas furnace from work cus I cant afford what the stores want to charge and I know its the something have you ever tried that or am I wasting my time I know there High cfm I mean they allow about a 300 ft run on a gas furance, and I would have to make sure it was a 120v but I need to go one of the routs Im just not sure witch one

 

[guest 77721]

I check designs by asking what the total wattage is and then I can figure out what the fan size is using the formula CFM = 3.16 * Watts/ Delta T for a 10* rise above room temps.

Most people use 4" fans which needs a 25 sq intake size or a 5"x5" square duct.

You don't need to use a furnace blower unless you are using a scrubber. Computer fans can do for most of your ventilation needs as long as they aren't blocked up.

I would avoid using 1" PVC. Most people think they can substitute four 1" holes for a 4" hole where 16 1" holes is the real equivalent.

It's more important to put your exhaust fan as high as possible to collect all the heat at the top of the box.

Check out Anti's thread. It's a multichamber design done right.
https://www.icmag.com/ic/showthread.php?p=2220492#post2220492

 

[dnotrem]

Wow thanks red you are an unlimited tap of useful information I could ask you questions for days but I don't want to keep intruding. And I check out the lodge you have more tutorials then the forms do. Honest I'll be browsing prob for the next month I get lost trying to read it all. I would try and add you as a friend but I can't figure out where it is for the life of me. The site needs to be rearutectured from scratch. You would think with it being the #1 growers form they would throw a little doe ray me into it. But you can't find the same knolage or quality of grower anywhere I know I'm learning the trade from the best. There is too much misguiding info anywhere els everyone thinks they know it all but again I keep rambling I'll keep you posted on how my first real cab goes if you want it would be nice to bounce idears off. Thanks for all the help I never thaught I would understand cfm's how I do now I can wait to show off to my new knolage of air flow to my boss hes going to shit bricks thanks red it's been a pleasure

 

[guest 77721]

Oh I'm full of it fer sure... LOL

There's lot's of info and great guys on this site. You really have to do a ton of reading but it's fun.

I use the Subscribe to thread function and the My Active Threads search off the user menu as a way of bookmarking threads.

If you wanna see the best ideas, check out Pontiac's Link O-Rama in my sig.

 

[FreezerBoy]

Rep points for Red. He da Man!

 

[bobman]

Maybe you guys can help me. I am thinking about two ways to vent my room.

I have a 10x10 flower room, with 2 small ac's running and a lot of fans. My temps are not bad but I would like to cut one of the ac's, or not even use ac during the cooler months. I live in a hot location.

1. I would either connect two vented hoods and have a 8" fan pulling air out the room. The first hood would be open. I would not be pulling air from outside the room.

2. I would just use a squirrel cage or 8" vortex in the top corner of the room to pull air out the room. Again no intake.

I guess my question is how are these ideas effected by not bringing air in from the outside.

 

[guest 77721]

To blow air out it has to be sucked in from somewhere. All a big exhaust fan will accomplish is building up negative pressure and without a proper sized intake, it will draw some outside air in from where ever it can.

I don't know what your outside temps are but I'd be looking for a way to get an intake installed if you can make use of it during the cool months. What's the deal with the no intakes?

 

[Lazyman]

Also check my sig, I wrote a very lengthy article on ventilation and more broadly, grow room cooling.

 

[bobman]

basically, I would intake and exhaust the air from the room right next door. There is no ac in that room and summer temps, without dumping heat from the lights, are probably around 80 (at night when I run my flower, room). But I have done no temp reading.

 

[guest 77721]

You need a heat sink of some sort to suck up all the heat. An 80 degree room is too hot to exchange much heat. Most fresh air ventilation systems run around 10* above room temperature so your room will be running in the 90's.

Lazyman's article is a good read about setting up growroom AC systems.