Grow Room Questions About Heating/Cooling/Odor Control

Discussion in 'Growroom Setup' started by GP73LPC, May 2, 2010.

  1. GP73LPC

    GP73LPC Registered+

    I am planning on enclosing a little cavity corner in my garage that will create a 3' x 5' room. It will be rather easy to connect it to my central heat/air but i worry about odor control.

    i have successfully used some very small ozone generators inside cabinets in the past. those along with exhausting through activated carbon worked very well. only one strain was ever detectable by smell. with that said i will definitely be using 1 or 2 of these small ozone generators.

    the room will be semi-sealed in the sense that i want to use my central heat and air, but i will not allow the room's air to be re-cycled back into my home's HVAC unit. since i have no plans on venting an exhaust from the room the potential odor could drift back into the duct work and stink up the whole house, which would be a disaster.

    so how do i go about preventing that?

    1. a small computer fan blowing into the room right at the point of entry of the duct work?

    2. a carbon scrubber right at the point of entry of the duct work?

    3. a combination of 1 and 2?

    or should i consider a portable a/c and portable heater in a totally sealed room? the cost of running a portable a/c and/or heater is something i am not to excited about. however, the idea of adding 140 cubic feet to my existing HVAC is much more appealing... ;)

    so hit me up. what are your recommendations? experiences?

    thanks :jointsmile:
  2. irydyum

    irydyum Registered+

    If i'm reading this correct, you are planning on using an existing vent to provide cool/heat and not a return vent.

    If you want to prevent any backup of odors you need to keep a negative pressure inside the growspace. The only real way to do it is with an exhaust fan, which means treating exhausted air with a scrubber. A 3x5 space doesn't require a huge fan or anything, but you must maintain a negative pressure. If the pressure becomes positive it will push out through any imperfections in the seals around your room and door.

    Try as we all might, i really don't think there is gonna be a way around this one.

    If you could run portable ac and have a 100% seal, that's a different story. Just a whole different set of circumstances to deal with at that point that i'm too stoned to ramble on about.

    Do a search for "noobs guide to growrooms" or something close to that. Great info on room set up in there:thumbsup:
  3. GP73LPC

    GP73LPC Registered+

    the vent is not an existing vent, it would be new. the duct work is just a few feet away in the attic, so it would real easier to add it.

    i understand negative pressure very well as i have had cabinets that used a passive intake and a positive exiting chamber. in that exiting chamber was an ozone generator and a carbon scrubber at the final exit point. that technique would work for this room also i believe. and the exhaust would be into my attic.

    the issue with a negative pressured room is maintaining temps in the house without drastically increasing costs. this room will be insulated and take on the temps of the house, however with a constant negative pressure what effect will that have on the house? the negative pressure would be a constant pull of air from the house (whether a/c or heat was running or not). the room would still pull it's air in from the duct work and threw the return air vent and thus from the air in the house itself. basically the entire house would become a negative pressure environment, albeit very little pressure...

    the air movement through out the house will not be a bad thing, but what kind of effect on temps and thus cost will this have on my house. always pulling cool air out of the a/c system basically and pumping it into the attic. to me it would be like leaving a window slightly open with the air conditioner running...

    with even a small little 90 cfm computer fan exhausting the room, the air would be exchanged about 45 times an hour. if my calculations are correct this could result in 5400 cf per hour being exhausted into my attic. so essentially in theory, i would be turning over all the air in my house every 3 hours. sounds expensive to be constantly losing all that cool air.

    i wonder if after scrubbing the air if it wouldn't be better to pump it back into the room somehow ???

    the second method with a portable a/c is doable. the issues i see there are:

    1. room must have a tight seal to prevent odor leaking out
    2. costs of running an 8 or 9 amp air conditioner

    EDIT: btw, checking the thread you mentioned...
    Last edited: May 3, 2010
  4. GP73LPC

    GP73LPC Registered+

    i've now read the most of the grow room setup thread, thanks :thumbsup:

    ok a couple more observations...

    when i computed the cubic feet and air movement, i used a 90 cfm computer fan as my base. i have done a little research today and have found that i can get a computer fan with cfm ratings that are much lower. so let's just use 25 cfm as my base. so now let me do some re-calculations.

    -3'x5'x8' sealed room with one active exhaust (computer fan, 25 cfm sucking the air from the room through a carbon scrubber)
    -passive intake (except when heat/air are running. i need to find out what the output cfm is for my HVAC)
    -120 cubic feet in the room (roughy 15,000 cubic feet in my house)
    -LED's and CFL's for lighting so heat will be very minimal.

    assuming the HVAC output in cfm doesn't over do the computer fan i can maintain negative pressure in the room.

    so with the lower cfm fan i can reduce how much air i am actually pulling out of my home and exhausting into the attic. if my re-calculations are correct it would take 10 hours to suck all the air from house. of course where i live the A/C is running frequently, so i think the loss of cool/heated air would be minimal...

    a question for some of you who might know; what kind of output in cfm does a 3.5 ton HVAC unit put out? What i don't want to do is create positive pressure in the room... on a side note, i could create a passive output as well with another carbon scrubber for when the A/C is running. That way i could prevent any positive pressure issues....

    as far as returning the scrubbed air to the room, i think that would cause positive pressure issues also, so i am scraping that idea.

    anyone else have comments/questions/advice?

    thanks :jointsmile:
  5. irydyum

    irydyum Registered+

    We need some people who have used CPU fans for exhaust to chime in. I think you are on the right track principally, but I dont think a small cpu fan is going to cut it. I don't think their CFM ratings apply to a large environment?? Not sure, but something is screaming at me that it won't be enough.

    How about instead of investing in cooling, invest in CO2. It will allow you to run much higher ambient temps, especially if you go the LED route. It also won't cost nearly as much to run. Just another thought. You could keep the room sealed throughout lights on, and you could run a single exhaust with a carbon scrubber on a thermostat or timer. I don't run CO2, but I'm sure someone can chime in that does:thumbsup:

    How about installing a backdraft stopper at the point where your A/C is going to enter the room. It's like a one way valve almost where the pressure from the a/c should open and close the vent as it goes on/off. Just throwing ideas out.
  6. GP73LPC

    GP73LPC Registered+

    hey thanks again...

    i am not sure and you may be correct about the pc fans (i am not referring to a little 2 or 3 inch CPU fan, but the larger PC Case fans, 4-5 inches). I have used them in 20 cubic foot cabinets very effectively... :thumbsup: they do have them that run at 100 cfm and up. that would effectively change the rooms air out about once a min... of course that is assuming the little fan could effectively cover the entire room and not just a portion of it.

    the C02 idea i like, but this room will have to cooled. temps can go to 110 degrees here in the summer :( and down into the 20's in the winter. i just see no way around some kind of temperature control.

    the carbon scrubber exhaust on thermostat and backdraft stopper on the a/c duct work are idea's to consider. however to keep a negative pressure in the room and i think i must do that because of pumping A/C into it, i am not sure if either of those ideas would work.

    but hey with that said, i appreciate your idea's... if you have more let me hear them... this is the time for idea's and brainstorming :jointsmile:

    i really want to do this room up correctly... btw, i am planning on creating a hidden door disguised as shelving to completely conceal the existence of the room... the hidden door will have an electro magnetic lock on it that is controlled through a programmable remote keypad ;)
  7. GP73LPC

    GP73LPC Registered+

    i was just digging through some boxes in the garage and found a couple of old (brand new) 5 inch computer case fans. these things really do move a lot of air. now whether it can handle a 3x5x8 foot room is still in question.

    i am gonna run a few tests.... :thumbsup: i happen to have a utility room with a doggie door that is very similar in size as to what i have propsed building.

    i can easily stick one of these fans in the doggie door, light up a smoke and hold it as far away from the fan as possible. if it is powerful enough i would expect to the the stream of smoke head off in that direction... ;)
  8. irydyum

    irydyum Registered+

    Rock on, nothing teaches quite like hands on:thumbsup: I'll be interested to see what you come up with as far as results go.
  9. GP73LPC

    GP73LPC Registered+

    ok, testing complete...

    first off, i looked up the model fan and found out it is an 88 cfm fan, which is whipping pretty good for a little DC computer fan.

    so first i sealed underneath the door leading from the utility room to the kitchen to try and simulate a sealed room. the only openings were the a/c vent and a ceiling (bathroom style) exhaust fan. a/c in the house was not running. i sealed the computer fan in the doggie door and lit up a cigar.

    smoke is lighter than air :( doh !!!!

    and the fan did not have enough power to suck the smoke out until the cigar smoke was about 2 feet away.

    so then i decided to just try the 50 cfm ceiling exhaust fan. it worked but the smoke had to get within about 1 foot for it to really move the air quickly.

    next, i taped up and sealed the computer fan to the opening in the existing exhaust fan. the 88 cfm computer fan was definitely an improvement over the 50 cfm bathroom fan.

    so what does all this tell me...

    well it tells me that one of these fans would probably be enough to maintain an negative pressure on the room. two would work better, but it might be too much movement. i really just want a minimal negative pressure on the room which would allow the ozone generator(s) to do their job. i really think this style fan(s) would work.

    i don't want a big, noisy squirrel fan with a huge cfm rating. i am looking to maintain minimal negative pressure without noise and without sucking the cool air out of the room to fast.

    these are definitely going to be tested more when the room is built. it might be that i need two of them positioned in two different spots with a carbon scrubber in front of each one.

    the main objective is to exhaust the room of any potential odor in a slow but steady manor...

    i feel decent about what i just saw. :thumbsup:

    btw, i plan on building a DIY scrubber that Bodom Children Of built here...

    also, the small ozone generator(s) i plan to use are this one...

    and i even considered putting up a timed OZIUM mister...

    i believe with all of these options i should be odor free :thumbsup:

Share This Page