Ventilation...Serious HELP needed...lots of pics!

Im building my first grow room and am in the heart of the build stage (see the pics). I want to start running my ducting and setting up my ventilation system, but need to decide EXACTLY what i am going to use and how.

The room main room is 10x11, there are two sectioned off room in the main room (the flowering and veg room). Check out the diagram of the room to get an idea of the setup and ventilation system.

I need to figure out what CFM each of those fans need to be to ensure excellent air flow with the correct amount of negative pressure and enough exhaust to control odor. (The fans are orange box's in the diagram).

So in order to figure out was size fans I need to adequately ventilate this room while having negative pressure (more out than in) there are equations (different and contradicting equations as seen in a post by desertrat recently).
The 'equation' I initially used is that you want to be able to remove all the air in the room in 5 minutes.

So I did the calculations to find the exact volume of the entire main room first:

Volume = L x W x H

I will do this volume equation in two steps because my room is not a simple cube but rather a cube AND a ‘3-d triangle’ (cant remember the name of that polygon lol).

So the part of the room that is a cube:
9.8’ x 10.8’ x 4.2’ = 444.5 ft^3

Now the triangle roof part:
Volume of 3-d triangle = ½ x base x height x length
½ x 10.8’ x 2.3’ x 9.8’ = 121.7 ft^3

Now I simply add them both together to get the entire volume of the entire grow room:
445.5 + 121.7 = 568 ft^3

So if I want to remove all the air in the room in 5 minutes I divide that number my 5 to get what cfm exhaust fan I need. 568 ft^3 / 5 minutes = 114 cfm

But looking at other peoples set ups they are using much bigger fans with similar sized rooms. I was reading that I can go with a bigger exhaust fan and not hurt anything besides my wallet, probably worth it in my opinion. So what size you think? Also what size filter?

But I don’t even know if doing that equation figures anything out because the room is divided into sections so there isn’t even that much air volume available to extract I don’t think, UNLESS because the flowering and veg room have fans BLOWING air into the main room does that air entering the room faster make there be more air then in the room by volume? (I hope that makes sense).

I need to figure out what size and types of fans to use for all these. This is a bit overwhelming if I must do separate equations compensating for air that is leaving and entering each room and then extracting it all from the main room…..

Anybody up for helping me out?

BTW-You guys kick ass, I have learned just about everything I know about growing from this site, you rock!

PS-I know I kinda posted something about this is an ealier thread so sorry for a bit of a double post but it was buried in another thread and am hoping to really get some good help on this cause I need it to be right.

i'll agree that 114cfm fan is by far not enough for that much space.

don't ask me what you need but that just sounds much to low.

someone should come along and help soon enough. i myself would love to see that perfect "attic" become a grow room.

hey nickibus,

got some new ideas, thought i'd share. first, check out the thread - https://www.rollitup.org/grow-room-design-setup/105781-how-much-air-exchange-do.html . the high end of the range is now 10 exchanges per MINUTE. so in all practical purposes, no one knows - too many factors to guess at without doing a full blown hvac design.

my suggestion for your sized room - get a 6" inline fan with 440 cfm for the main room exhaust and 4" inline fans with 170 cfm for the lights. buy variable controllers and dial down the fans to get the airflow you need to cool and get rid of odors. you want to use the lowest speed possible to reduce sound.

as long as you have a passive intake (a hole) to let air in you don't have to worry about pulling enough air into the room.

Ok thanks desertrat!
What size fan for the main room intake?
What size fans for the flowering and veg room intakes?

By "passive intake" do you mean no intake fan just a hole? Or do you mean a hole in the main room in addition to the main room fan?
Should the passive intake and intake fan (if you are saying both) feed from the outside or just the attic?

think about this modified design.

1. put the two lights in line with each other and pull air through both with a single 170 cfm fan.
2. put the two rooms in line with each other with another 170 cfm fan pulling air from the veg room to the flower room.
3. use all passive intakes (yes, just a hole - with a manual damper to adjust the incoming air) except for number 2.
4. move the passive intake for the main room as far away from the ac and passive intake for the veg room so that the air entering the grow rooms is as conditioned as possible.
5. put variable speed controllers on all fans
6. manually adjust each fan and each passive intake to get good ventilation and odor control.

see modified diagram below. btw, this is helping with my second grow room design so i've put a little extra thought into it. i did not go for the cheapest design but it does use what you buy very efficiently.

Desertrat,

Hey man so Ive been working on the room for days (more or less the electrical and plumbing and have kind of rethought the room set up...I realized there is less space then I thought and having the rooms like they are in our drawings doesnt leave much space.

So I came up with this (I did it very fast so forgive the shityness of it)...

Anyways, what do you think and if I do this set up for the rooms how could I do my intake and exhaust? With this set up all my exhaust runs out in that far right corner but would be conceled when rooms are up (will make an access to that area obviously through either the flowering or veg room....

Also, I am framing in a small 2x2 area for the AC unit so it doesnt sit in the middle of the room (like in diagram).



What do you think?

ventilation can still work basically the same way as before. put the carbon filter in the flowering room and pull the air from there into the veg room. then separately pull the airfrom the veg room out of the house. add a passive vent for each of the grow room. its really the same design with the rooms moved.

why wouldn;t that work?

ps - still no answer on fan sizing

Do you mean have the carbon filter in the veg room pulling the air out from that room??

Because if the carbon filter is in the flowering room pulling to the veg room then it going out that room out of the house that air will be contaminated with the passive vent in the veg room and also these walls arent air tight for the veg and flowering room...

Or am I just misunderstanding what you said?

Could be... bongsmile

the theory behind this setup is that typical strains do not smell much until flowering. if you keep your flowering room door closed then the smell will be concentrated there and your filter will be more effective. but on second thought its a better design anyway to go from veg room to flower room without a filter and the separately from the flower room through a filter and then out of the house. double sure that way.