scruffy420
New Member
So, I'm working on a design of my own, and I have most of it down. The problem is that I'm having trouble calculating the proper ventilation needs. I have a fairly niche case, and I'm looking for help with it, if there are any HVAC-savvy people out there. Since, I'm doing this myself, I'm of the persuasion of go big, or go home (although, this will be at home 
). It should be known that I'm a crazy person, and am probably going over the top, but I'm an engineering student, and I'm having so much fun, I can't stand it. I want each room to be completely air-tight (done), light-tight (done), silent (can-do), and smell free (<- most important, also done).
Of note, the rooms are setup as such (also, my profile picture is the actual layout of my setup, though not to scale, haha. I can't figure out how to just upload the picture to here, so I apologize. I don't know if it's even big enough for you to see, but hopefully you can get a basic idea of it)(EDIT: I just figured it out, the link should now be included as a comment below this post!) :
-5x5 Veg/trim room first, with 2x5 being veg, and 3x5 being a sitting area for trimming and storing nutes etc. Inlet filters are installed at the front end of each area, near floor level, as they are separated by a wall. They will be passive intakes. There will be an access door in this room, from outside the enclosure.
- Flower room is between the veg and vent rooms: 5x5. A door will exist between the sitting/trimming area, and the flower room. (Note: not in the actual veg portion of the first room)
- Vent room is last, and is completely sealed off from the two, with the exception of the two carbon filter lines that run through the wall from the flower to the vent room. the vent room will have 2 10" penetrations to outside the enclosure, for exhausting the air.
So, here are my ideas, and current set up:
- Total dimensions: 12'x5'9"x8' (LxWxH): These dimensions also include the walls, which will each be ~4.5" thick (a total of 4 walls).
- Three adjacent rooms: a 5'x5' Trimming/Veg room, a 5'x5' Flower room, and a 1.5'x5' Ventilation room. All rooms will have a height of 7.5'.
- The ventilation room will house my exhaust fan, required piping, and noise silencer.
- The flower room houses my carbon filters, supply fan, and required piping.
My setup is a bit of insanity, so bare with me here, and if you can visualize the rooms, that would be great!
Exhaust:
- 2x 8" carbon filters - each of these are ran through 8" permanent round ducting through the wall that connects the flower room to the vent room.
- A "T" junction connects the piping from the exhaust side of both filters, placing them in parallel, and giving me one exhaust pipe.
- An 8" to 10" "reducer" increases piping size to allow the placement of a 10" fan
- The 10" Phresh Hyper Fan is then connected to the system, in a "pull mode", exhausting air out of the flower room.
- 10" Flow silencer is installed on the exhaust side of the fan
- A 10" "T" junction splits flow back into 2 lines, which are ran to the outside edge of the box, through the wall, and form the actual exhaust ports for the system.
Supply:
- Original:
- I wanted to use just passive intake, however, I also want my veg/trim room ventilated, as my young plants need fresh air, and I have heard that harvesting is the smelliest part of the adventure, so I don't want that getting out. So, I have to have a way to connect the veg room to the flower room.
- Problem:
- After doing some initial calculations, it looks like my 10" fan will not actually be able to generate enough static pressure to achieve a flow rate high enough for proper ventilation, if I simply connect the two rooms together. My total volume to be ventilated is 375 cu. ft. I need to generate at least 3" H2O of static pressure for this to even possibly work. I'd like a bit more, to achieve a higher flow rate.
-Proposed solution:
- Add a 6" Phresh Hyper Fan, aligned as a second source of "pull", located in the flower room, and pulling through a setup very similar to my flower room exhaust. This idea led me to the thought of "Well, if I'm adding a second fan that's going to actually blow air INTO my flower room, why not make it work for me? I can add a bit of ductwork to the situation and route the piping to the bottom of my flower room, and then point the ducts at my flowers, which will blow air across them, thus eliminating the need for a circulating fan inside the flower room. Also, most circulating fans run a higher power draw than the 6" fan, so it actually saves energy, which is a bonus!". The system will include 2x 6" ducts as intakes, one drawing from each area of the veg/trim room. They will be placed near the ceiling (furthest point from the inlet filters, and this also helps in that it allows me to utilize the pressure exerted by the air due to the Pressure-Fluid Height relationship). These ducts will run to a "T", and form the inlet to the fan. The fan will be attached so that it sucks air from the veg room, and there will be a silencer attached. A 6" to 4" reducer will be placed at the outlet of the silencer so that it causes the air in the duct to travel faster, as this will promote air mixing in the room, and cause a higher air speed across the plants, which is the whole purpose of running the extra ducts. The outlet for the fan will be run and split into four parallel branches (from a pressure standpoint; they don't necessarily have to be geometrically parallel). Each of the four ducts will run to the walls, and then run down the sides, near the floor, and pointed at the growing area of each of the (4) pots I'm looking to be flowering, at a time.
- Parameters:
- My inlet filters (in the veg/trim areas) are simple 10"x10" HVAC filters (or 20"x20", dependent upon what sort of air velocity I want, to include the balancing of the flow rates in each of the veg and trim areas of the first room). Their initial static pressure drop is low; Approximately .25" H2O. However, I don't want to replace filters every month, because that can become very costly, so I'd like to design the system to be able to operate up to the rated capacity and pressure drop of the filters, which is ~1" H2O.
- I want to do this with one fan, and since my trim and veg areas are going to be closed off by a door, I need to run two vent ducts; one from each area, into the flower room, where the fan will be mounted.
- I want the fan to be quiet, which I can solve on my own, after the system is built. The one thing I would like included in the system is a flow silencer, and there will be a veritable boatload of air moving in this piping.
- I want ducts ran to each approximate flowering area, to circulate air in my room, and give the plants the little bit of air movement they need to build good, strong stems.
- Issues with design:
- My biggest issue is that I can't really find information that covers the corner case that I'm experiencing. I need to be able to figure out how operating two different fans, with different output pressures and flow rates will affect each other, when operating. I do know pump laws, and flow characteristics such as speed of the pump in relation to pump head, flow rate, and horsepower (or just power draw, in this case) of the pump, and I'm pretty sure that the two pumps will operate at a point where their two flow graphs intersect. What I don't know, is if the 10" fan will overspeed the 6" fan, and wear it down faster, or if I'll be just fine with simply placing the 6" fan in the new ducting, turning it on, and letting it do its thing. The total output pressure of the two fans adds up to ~ 4.56" H2O, which should be enough to overcome system resistance and give me what I want, but it is also a possibility that I'll need the 8" fan as my "supply" fan. My biggest issue is that this is such a weird thing to be looking to do, that I can't find solid answers to my dilemma online, so I can't find out if it'll work or not. I've done simply too many calculations, (I am fairly experienced with fluid flow, and fluid/thermodynamics.) and still cannot figure it out.
- Conclusion:
I appreciate any help that I can get with this; I know there's gotta be someone on the site who knows, or at least has some idea of, what I can do to solve the problem. It's frying my brain. I am, however, a minimum of 8-12 months from starting this project, as I have some stuff going on right now that precludes me from buying anything, as it is just too expensive. I understand that my project is expensive, and if your idea/solution seems really expensive, that's okay. I expect it. This is a long-term project, and I want it to be a permanent growing area. It's an investment for me. So, all ideas are welcome, and I really do appreciate any insight that you guys have! Thank you in advance, and I hope everyone here a joyous time!
). It should be known that I'm a crazy person, and am probably going over the top, but I'm an engineering student, and I'm having so much fun, I can't stand it. I want each room to be completely air-tight (done), light-tight (done), silent (can-do), and smell free (<- most important, also done). Of note, the rooms are setup as such (also, my profile picture is the actual layout of my setup, though not to scale, haha. I can't figure out how to just upload the picture to here, so I apologize. I don't know if it's even big enough for you to see, but hopefully you can get a basic idea of it)(EDIT: I just figured it out, the link should now be included as a comment below this post!) :
-5x5 Veg/trim room first, with 2x5 being veg, and 3x5 being a sitting area for trimming and storing nutes etc. Inlet filters are installed at the front end of each area, near floor level, as they are separated by a wall. They will be passive intakes. There will be an access door in this room, from outside the enclosure.
- Flower room is between the veg and vent rooms: 5x5. A door will exist between the sitting/trimming area, and the flower room. (Note: not in the actual veg portion of the first room)
- Vent room is last, and is completely sealed off from the two, with the exception of the two carbon filter lines that run through the wall from the flower to the vent room. the vent room will have 2 10" penetrations to outside the enclosure, for exhausting the air.
So, here are my ideas, and current set up:
- Total dimensions: 12'x5'9"x8' (LxWxH): These dimensions also include the walls, which will each be ~4.5" thick (a total of 4 walls).
- Three adjacent rooms: a 5'x5' Trimming/Veg room, a 5'x5' Flower room, and a 1.5'x5' Ventilation room. All rooms will have a height of 7.5'.
- The ventilation room will house my exhaust fan, required piping, and noise silencer.
- The flower room houses my carbon filters, supply fan, and required piping.
My setup is a bit of insanity, so bare with me here, and if you can visualize the rooms, that would be great!
Exhaust:
- 2x 8" carbon filters - each of these are ran through 8" permanent round ducting through the wall that connects the flower room to the vent room.
- A "T" junction connects the piping from the exhaust side of both filters, placing them in parallel, and giving me one exhaust pipe.
- An 8" to 10" "reducer" increases piping size to allow the placement of a 10" fan
- The 10" Phresh Hyper Fan is then connected to the system, in a "pull mode", exhausting air out of the flower room.
- 10" Flow silencer is installed on the exhaust side of the fan
- A 10" "T" junction splits flow back into 2 lines, which are ran to the outside edge of the box, through the wall, and form the actual exhaust ports for the system.
Supply:
- Original:
- I wanted to use just passive intake, however, I also want my veg/trim room ventilated, as my young plants need fresh air, and I have heard that harvesting is the smelliest part of the adventure, so I don't want that getting out. So, I have to have a way to connect the veg room to the flower room.
- Problem:
- After doing some initial calculations, it looks like my 10" fan will not actually be able to generate enough static pressure to achieve a flow rate high enough for proper ventilation, if I simply connect the two rooms together. My total volume to be ventilated is 375 cu. ft. I need to generate at least 3" H2O of static pressure for this to even possibly work. I'd like a bit more, to achieve a higher flow rate.
-Proposed solution:
- Add a 6" Phresh Hyper Fan, aligned as a second source of "pull", located in the flower room, and pulling through a setup very similar to my flower room exhaust. This idea led me to the thought of "Well, if I'm adding a second fan that's going to actually blow air INTO my flower room, why not make it work for me? I can add a bit of ductwork to the situation and route the piping to the bottom of my flower room, and then point the ducts at my flowers, which will blow air across them, thus eliminating the need for a circulating fan inside the flower room. Also, most circulating fans run a higher power draw than the 6" fan, so it actually saves energy, which is a bonus!". The system will include 2x 6" ducts as intakes, one drawing from each area of the veg/trim room. They will be placed near the ceiling (furthest point from the inlet filters, and this also helps in that it allows me to utilize the pressure exerted by the air due to the Pressure-Fluid Height relationship). These ducts will run to a "T", and form the inlet to the fan. The fan will be attached so that it sucks air from the veg room, and there will be a silencer attached. A 6" to 4" reducer will be placed at the outlet of the silencer so that it causes the air in the duct to travel faster, as this will promote air mixing in the room, and cause a higher air speed across the plants, which is the whole purpose of running the extra ducts. The outlet for the fan will be run and split into four parallel branches (from a pressure standpoint; they don't necessarily have to be geometrically parallel). Each of the four ducts will run to the walls, and then run down the sides, near the floor, and pointed at the growing area of each of the (4) pots I'm looking to be flowering, at a time.
- Parameters:
- My inlet filters (in the veg/trim areas) are simple 10"x10" HVAC filters (or 20"x20", dependent upon what sort of air velocity I want, to include the balancing of the flow rates in each of the veg and trim areas of the first room). Their initial static pressure drop is low; Approximately .25" H2O. However, I don't want to replace filters every month, because that can become very costly, so I'd like to design the system to be able to operate up to the rated capacity and pressure drop of the filters, which is ~1" H2O.
- I want to do this with one fan, and since my trim and veg areas are going to be closed off by a door, I need to run two vent ducts; one from each area, into the flower room, where the fan will be mounted.
- I want the fan to be quiet, which I can solve on my own, after the system is built. The one thing I would like included in the system is a flow silencer, and there will be a veritable boatload of air moving in this piping.
- I want ducts ran to each approximate flowering area, to circulate air in my room, and give the plants the little bit of air movement they need to build good, strong stems.
- Issues with design:
- My biggest issue is that I can't really find information that covers the corner case that I'm experiencing. I need to be able to figure out how operating two different fans, with different output pressures and flow rates will affect each other, when operating. I do know pump laws, and flow characteristics such as speed of the pump in relation to pump head, flow rate, and horsepower (or just power draw, in this case) of the pump, and I'm pretty sure that the two pumps will operate at a point where their two flow graphs intersect. What I don't know, is if the 10" fan will overspeed the 6" fan, and wear it down faster, or if I'll be just fine with simply placing the 6" fan in the new ducting, turning it on, and letting it do its thing. The total output pressure of the two fans adds up to ~ 4.56" H2O, which should be enough to overcome system resistance and give me what I want, but it is also a possibility that I'll need the 8" fan as my "supply" fan. My biggest issue is that this is such a weird thing to be looking to do, that I can't find solid answers to my dilemma online, so I can't find out if it'll work or not. I've done simply too many calculations, (I am fairly experienced with fluid flow, and fluid/thermodynamics.) and still cannot figure it out.
- Conclusion:
I appreciate any help that I can get with this; I know there's gotta be someone on the site who knows, or at least has some idea of, what I can do to solve the problem. It's frying my brain. I am, however, a minimum of 8-12 months from starting this project, as I have some stuff going on right now that precludes me from buying anything, as it is just too expensive. I understand that my project is expensive, and if your idea/solution seems really expensive, that's okay. I expect it. This is a long-term project, and I want it to be a permanent growing area. It's an investment for me. So, all ideas are welcome, and I really do appreciate any insight that you guys have! Thank you in advance, and I hope everyone here a joyous time!
add some ceiling/wall vents or passive fan vents 
The reason your brain is hurting is you have forgotten the 1st rule of engineering: (many do LOL) KISS. You are over thinking your problem and over complicating it.
