Screenshot: New Box - Need Opinions!

Hey everyone, I recently had a male plant from bagseed, and it's time for a fresh start. This time around I have some feminized coming my way, so with that out of the way, I feel the need to build a new cab. I should say tent, because it'll be a PVC panda film concoction. My first cab worked exceptionally well, I did a great job building it, but I realized that I'd like a dual chamber setup.

Anyway, here is a picture of what I did in SketchUp. I didn't feel like making it look like PVC, so just use your imagination!

Opinions are greatly appreciated!



The tent will be made from 3/4" PVC @ 6' H x 5'10" L x 2' D, which will leave me with 2' x 2' for each chamber and a 1'10" x 2' section in the middle for my fan/filter.

I don't have the cash to blow on another filter, so I decided to make the one filter do double duty. The front of the tent will obviously be covered by some PVC/panda film panels made from 1/2" PVC instead of 3/4. I should be able to velcro those to the 3/4" nicely.

Let me know what you guys think!

Thank you!

Double duty? how exactly will that work?

Put a few passive intakes low and locate the filter and fan as high as you can. This will maintain negative pressure [while the fans are running] bringing in new air and taking all of your hot air out.

The scrubber on the floor is breaking the rule of physics.

Otherwise, very interested to see where this is going! Dope setup!

Which rule of physics is this breaking. Looks like a fine idea to me. Hot air enters the fan /exhaust chamber at the top, gets pulled back down and exits. Also creates a perfect light trap. I'm no physics expert admittedly, but this looks sweet to me.

Abiqua said:

Double duty? how exactly will that work?

Put a few passive intakes low and locate the filter and fan as high as you can. This will maintain negative pressure [while the fans are running] bringing in new air and taking all of your hot air out.

The scrubber on the floor is breaking the rule of physics.

Otherwise, very interested to see where this is going! Dope setup!

Click to expand...

I could use some clarification.

By double duty I mean that I can use a single fan/carbon filter for veg and flower chambers simultaneously.

The only downside I see with this design is the fact that the hot air stays in the system a little longer because it has to travel down to the filter. However, I don't see this being a huge problem.

Other than that, this design seems pretty efficient. Like Mewk said, the hot air is vented, and a light trap created.

Also, negative pressure should be achievable no matter where the exhaust is placed as long as the intake to exhaust ratio is maintained, right?

Can anyone else chime in on this?

Thanks again.

The scrubber on the floor is breaking the rule of physics.

Click to expand...

I think he just mean heat rises, take advantage of the way nature works. Great looking sketch up.

reku said:

I think he just mean heat rises, take advantage of the way nature works. Great looking sketch up.

Click to expand...

Thanks!

I didn't really see another way to vent each chamber and incorporate a light trap. I might stick with it just like this, but I'll tweak it some more and see what I come up with.

It looks nice, but I also think the shortest path of airflow possible is in your best interest and that could be another reason to have the fan at the top.

mc130p said:

It looks nice, but I also think the shortest path of airflow possible is in your best interest and that could be another reason to have the fan at the top.

Click to expand...

I certainly understand the concept. The top would definitely be preferable, but placing my fan at the top creates a new issue of light separation. The only reason it's at the bottom is because it enables me to build a light trap.

I have messed around with your drawing and think that you could possibly just invert your design and build a much smaller light separation chamber.

The filter itself can be used as light proofing. So if it somehow could sit in the top but both chambers connected to it securely and then light would be blocked from either side but not airflow. Your design already incorporates intake ports, so good there.

Nothing wrong with the original design, but inefficiency will rule because it will have to drag the air backwards, more pushing than pulling. So, have you sized a fan? This is where you can the test the inefficiency by using some rudimentary airflow math. Total CF, total CFM and averaging say 5-10 room changes per minute. If you can keep your temp within 24-27C and RH below 60% then your golden. But......if your room changes rise in relation to keeping humidity down, you will probably need a bigger fan or temp control device. The excess hot air is pooling in the conditions described and not properly venting.

Abiqua said:

I have messed around with your drawing and think that you could possibly just invert your design and build a much smaller light separation chamber.

The filter itself can be used as light proofing. So if it somehow could sit in the top but both chambers connected to it securely and then light would be blocked from either side but not airflow. Your design already incorporates intake ports, so good there.

Nothing wrong with the original design, but inefficiency will rule because it will have to drag the air backwards, more pushing than pulling. So, have you sized a fan? This is where you can the test the inefficiency by using some rudimentary airflow math. Total CF, total CFM and averaging say 5-10 room changes per minute. If you can keep your temp within 24-27C and RH below 60% then your golden. But......if your room changes rise in relation to keeping humidity down, you will probably need a bigger fan or temp control device. The excess hot air is pooling in the conditions described and not properly venting.

Click to expand...

Thanks for checking it out for me. I actually thought the same thing with the filter being the light trap, being half in each chamber, but I'm concerned about being able to implement it correctly. I know it's not efficient pulling air this way. I will see what else I can come up with.

I am am nowhere near 5-10 per minute. I'm using a 4" Sunleaves. Under ideal conditions I'm looking at 2.7 per minute based on approximately 72 cubic feet.

The tent will be in a climate controlled basement, although it is colder than the rest of the house. It'll be consistently below 27c, and the humidity never exceeds 50.

I will keep refining it.

Thanks for for the input!

Ok. I went back to the drawing board, and I made something larger and a little more efficient.

Let me know what you think!

Thanks!!!!



Here's another one. I'm so happy to have SketchUp 3d Warehouse.

Like the new concept but you might as well upgrade the fan before you build. go with a 6" high flow. Air exhange isn't just about getting the heat out. With these cabs that we build we also need as much CO2 as we can get and the more air exchanges you can get it the better your growth as the plant will not want for CO2. By controlling the temp in the box and at the same time bathing the plant in an abundance of CO2 you're helping her breath easy while she uses the water and light to make the fuel she burns to grow.

Spanky's Monkey said:

Like the new concept but you might as well upgrade the fan before you build. go with a 6" high flow. Air exhange isn't just about getting the heat out. With these cabs that we build we also need as much CO2 as we can get and the more air exchanges you can get it the better your growth as the plant will not want for CO2. By controlling the temp in the box and at the same time bathing the plant in an abundance of CO2 you're helping her breath easy while she uses the water and light to make the fuel she burns to grow.

Click to expand...

I was under the impression that air exchange at least once every 5 minutes was desired. With this setup, @ 56 cubic feet, and with my fan @ 200cfm, I'm looking at almost 4 cycles of air exchange per minute.

Do I still need a larger fan?

Well after you factor in the loss of flow do to the Pre-filter on the intake (keeps out bugs and light out of your box, I use carbon) and the Filter (go with a quality filter, they work and most can be used twice after cleaning....oh and you can pack your own carbon once that's done. no disrespect to the home brew but for bigger grow spaces you need a good filter) you won't be at 200cfm of air flow. Some manufactures state that in the ways that you can you use their product but most don't. Either way with the grow potential of the space your building you can get some great yields but that will require a lot of light and in an enclosed space a lot more heat. Don't forget even with the air flow going we are still trapping a lot of energy in a small space. Better safe then sorry going with the bare minimum will in the end in with those same results, the bare minimum. I'm not saying go big or go home but with that design and the work involved you're gonna end up doing just that later anyway.

https://www.icmag.com/ic/showthread.php?t=112862

This will help to finish it off, I think you are definitely pointed in the right direction.

Spanky's right on all points, and is there a way of knowing how many room changes without a bunch of fancy sensors?........yes, adjust for heat and humidity and you usually can't go wrong.

Negative air pressure is what your are trying to accomplish, by always having the bigger exhaust over an intake, fresh air, Co2 are brought in, stale oxygen [for plants] pushed out. Again, how much and how often is usually dependent on room temp and humidity, well RH%

I would get a quality filter, like Spanky is saying, I always argue about TINY diy carbon filters, but they make prefabs as low as 200cfm, so your golden. Try finding a quality filter under 200cfm, not many that I am aware of.......

Abiqua said:

https://www.icmag.com/ic/showthread.php?t=112862

This will help to finish it off, I think you are definitely pointed in the right direction.

Spanky's right on all points, and is there a way of knowing how many room changes without a bunch of fancy sensors?........yes, adjust for heat and humidity and you usually can't go wrong.

Negative air pressure is what your are trying to accomplish, by always having the bigger exhaust over an intake, fresh air, Co2 are brought in, stale oxygen [for plants] pushed out. Again, how much and how often is usually dependent on room temp and humidity, well RH%

I would get a quality filter, like Spanky is saying, I always argue about TINY diy carbon filters, but they make prefabs as low as 200cfm, so your golden. Try finding a quality filter under 200cfm, not many that I am aware of.......

Click to expand...

I actually have a very good filter. I bought a 4" x 12" PHRESH filter rated at 200 cfm, and my Sunleaves WindTunnel is rated the same.

I don't want to seem ungrateful for the information, but I'm just confused a little bit.

I own two California Lightworks SolarFlare 200's, so they are very cool running, so I don't see the temperatures being astronomically high. In my micro cab, using one of the SolarFlare's, my temps were only about 7 degrees above room temperature. Also, RH is regulated by my central-air conditioning.

Could I buy a bigger fan/filter? Yes, of course, but wouldn't that be a waste of money if what I have works? The only thing that is really an issue is the CFM drop due to the filter, and intake filters, but what if I quadruple the intake surface? Wouldn't that take care of that problem? Heat isn't an issue with these LED fixture, and I've used one in a tiny space only to see a 7 degree rise in temperature over room temp.

I will read that page for sure, Abiqua, but consider this.

Let's say I'm getting 4 cycles exchange per minute, and the recommended is 1 every 5 minutes... Will the carbon filter I have, and the intake filters realistically drop my 4 exchanges per minute down to 1 per minute, or even worse than that, 1/5 an exchange per minute?

I find this hard to believe..

Bottom line, I'm using LED's, and my fan/filter setup cost somewhere ~$200, and I don't see how, when looking at all the variables, it can be seen as bare minimum. Maybe I just want it to be adequate so badly that I'm overlooking something, but I just don't see where what I have isn't more than adequate...

No disrespect at all, I just want to be sure I'm not wasting money.

No offense taken at all. I'm not aware of the canopy penetration of LEDs. If they are anything like CFLs in that regard no you wont need more airflow, but you also don't need a 6' tall box either. How good are LEDs on lower growth?

Cool! I'm not aware of the canopy penetration of LED's either, but based on what I've read/seen/heard, it's most definitely better than CFL. The guy at California Lightworks told me not to let my plant get closer than 12" to the light, and I know that CFL's need to be WAY closer. Whether or not this says anything about the penetration of the light is another topic. According to some tests I see on YouTube, LED's can reach a pretty substantial PAR rating at significant distances. Again, I'm no pro.

Actually, this is only my second grow. My first was in a semi-micro cab with 1 SolarFlare 200 (https://www.rollitup.org/stealth-micro-cab-growing/718949-my-finished-cabinet.html). The fixture was way overkill, but it's what I wanted, so I did it. I did a SCROG because I wanted to make sure that penetration wasn't an issue, and I had no problems... Well, except the fact that it was a MALE! PHUCK!

The only reason I designed this thing at 7' is because I was going to attempt to grow "straight-up", and I didn't know how tall these plants can get. Ideally, I want to keep them smaller and bushier and, for that reason, I may just stick to SCROG. If that's the case, I can dramatically reduce the height, simultaneously reducing the airspace my fan/filter needs to process. I think I'll drop the height down to 6' instead. that should be more than enough, especially since I'll probably do SCROG or LST.

Thanks for making me think a little harder. It's good to get some outsider opinions. Shorter means less material cost, less physical labor (ha), and better efficiency with equipment I have. I like that.

* Option 2: Buy the same fan/filter combo and separate the chambers. Build both to 7' to accommodate placing the fan/filter inside the tent. Either way, I have some things to think about.

You can always build to separate tents and use a "y" duct adapter and ducting to vent to the fan then the filter. That will also eleminate the need for extra work blocking light contamination. Plus then you have the option of building the specific tents to yor needs. Perpetual grow, mother/cone, veg, flower, and the possiblities are endless.

Gravity Man said:

I actually have a very good filter. I bought a 4" x 12" PHRESH filter rated at 200 cfm, and my Sunleaves WindTunnel is rated the same.

I don't want to seem ungrateful for the information, but I'm just confused a little bit.

I own two California Lightworks SolarFlare 200's, so they are very cool running, so I don't see the temperatures being astronomically high. In my micro cab, using one of the SolarFlare's, my temps were only about 7 degrees above room temperature. Also, RH is regulated by my central-air conditioning.

Could I buy a bigger fan/filter? Yes, of course, but wouldn't that be a waste of money if what I have works? The only thing that is really an issue is the CFM drop due to the filter, and intake filters, but what if I quadruple the intake surface? Wouldn't that take care of that problem? Heat isn't an issue with these LED fixture, and I've used one in a tiny space only to see a 7 degree rise in temperature over room temp.

I will read that page for sure, Abiqua, but consider this.

Let's say I'm getting 4 cycles exchange per minute, and the recommended is 1 every 5 minutes... Will the carbon filter I have, and the intake filters realistically drop my 4 exchanges per minute down to 1 per minute, or even worse than that, 1/5 an exchange per minute?

I find this hard to believe..

Bottom line, I'm using LED's, and my fan/filter setup cost somewhere ~$200, and I don't see how, when looking at all the variables, it can be seen as bare minimum. Maybe I just want it to be adequate so badly that I'm overlooking something, but I just don't see where what I have isn't more than adequate...

No disrespect at all, I just want to be sure I'm not wasting money.

Click to expand...

Use the filter you have, I wasn't suggesting buying another one. I highly recommend reading the link, way more info than can be explained. Virtually the same example of your last design is being used.
Lots of graphs and charts that will answer your questions. [I wasn't suggesting looking for a filter under 200 cfm, I was just pointing out that the lowest CFM of factory made filters is generally around 200 cfm... I should have said, "dare you to find" because you won't, I was more following up on Spanky's response......]


I don't think you need to replace anything, but you won't know till you start running it and realize how your ambient temp and humidity are acting INSIDE the cab. Ton's of factors will affect this beyond the fan. How much will each plant evapostranspirate for instance, how will it affect humidity and how will it affect co2, none of these factors are directly related but can be indirectly related.

If the filter and the fan are sized correctly for your cab, then it won't affect temp/Rh that much, water, plants, inside variables will alter this more[incremental changes of a few degrees] than the fan combo.

Most people in micro start using fans, then don't realize how much they flow or start flowering and THEN add a filter on and heat rises. I think that is what Spanky is referring to.

Now go out and see if it works. Planning it on paper is one thing, but testing is another....