Negative Air Pressure

I'm sure someone out there has run into the problem we have which is negative air pressure in my house. We have two rooms a Veg and a Flower that we spent almost $10,000 on. We are running 2-12" Blower Fans for our vetilation system and they are inline with each other and vented outside. What these rather large fans have done is make my house Negative, in regards to air pressure. I have back drafting which is air being pulled down my fireplace which of course is bringing in CO, carbon monoxide, among other nice carsonogens (spelled wrong). I'm not sure what our dumb ass' were thinking when we designed this system, but now we are looking at a huge bill to equalize the air pressure unless someone has a great idea, maybe some HVAC guy? I did find a thing out of Canada, but it is going to run us another $1,000. Of course I'm not sure that will work either because they are talking about a problem being caused with the fans over your stove or the fan in your bathroom, not these 12" monsters that we have running 24/7!

You need more intake into the GR. A little negative pressure is good in your room so you don't get smells leaking out but obviously you have too much. Too much neg pressure in you room will pull in dirt, mold and other pollutants so I'm thinking you need to tone things down a bit.
Why are you not running a sealed room with air cooled lights and CO2? Using massive air flow to keep your room cool seems a little old school especially since you've spent so much already.

shiftgrow said:

You need more intake into the GR. A little negative pressure is good in your room so you don't get smells leaking out but obviously you have too much. Too much neg pressure in you room will pull in dirt, mold and other pollutants so I'm thinking you need to tone things down a bit.
Why are you not running a sealed room with air cooled lights and CO2? Using massive air flow to keep your room cool seems a little old school especially since you've spent so much already.

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I think you have this wrong we are pulling air down my chimney and any other spot in my house that may be open, but because it is Winter in Michigan it is drawing air down the chimney, hot water heater , and drying vent. What do these all have in common toxic gases and flames. I do not want to wake up dead, I guess I would not wake up, you understand. Both of our growing rooms are as tight as humanly possible, so nothing is being pulled into them. Of course our 4 1000W and 6 600W lights are air cooled, the room would be 200 degrees. The airflow was for the smell and the humidity.
Actually it is as simple as cutting a couple of big holes in the wall, but I do not particularly like that idea.

Push more clean outside airflow directly into the grow room. Pull your air for the hoods from somewhere outside the house, or the attic. You're sucking all the air out of the house through the grow room, and the house is equalizing pressure through the path of least resistance, i.e.. your chimny, vents, etc. If you pull the hood cooling air from outside, you should greatly reduce your negtive pressure.

omx1998 said:

I think you have this wrong we are pulling air down my chimney and any other spot in my house that may be open, but because it is Winter in Michigan it is drawing air down the chimney, hot water heater , and drying vent. What do these all have in common toxic gases and flames. I do not want to wake up dead, I guess I would not wake up, you understand. Both of our growing rooms are as tight as humanly possible, so nothing is being pulled into them. Of course our 4 1000W and 6 600W lights are air cooled, the room would be 200 degrees. The airflow was for the smell and the humidity.
Actually it is as simple as cutting a couple of big holes in the wall, but I do not particularly like that idea.

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Never can you overdo intake with a speedster hooked up to it.......I run 3 1000 watts in an 8x8 (2) 737 cfm can fans with a speedster to slow it down and that's that. Do over think.

Don't over think***** my bad the Tahoe Kush is pretty sweet...

You could do those lights in 2 tents....why kill yourself with necessary overhead?

Is your basement vented? Not talking about your grow room here just the basement where the furnace and water heater lives. They use air for combustion and usually older houses leak enough to supply this but is your negative pressure grow room is leaking even slightly, over time this will
pull air in from the rest of the house creating negative pressure and pulling the gasses back down the chimney.

I'm not suggesting cutting big holes in the wall! Perhaps your air in could be a bit less restrictive. Did you try a smoke test around your door seals at the grow room to check for leakage? It's nearly impossible to build a room that is completely air tight against a negative pressure unless you have steel doors like in a submarine. Positive pressure (which doesn't belong here but for demonstration only) is easier to seal because the pressure is pushing the door into the seal rather than pulling it away.

Unless I'm still not getting your drift, it seems to me that your negative room pressure combined with the negative effect created by your furnace and water heater combustion are the culprits.

You are blowing air from within your house out....your house is pulling air from the outside in to compensate...ie.negative presure....You have 12" @800cfm? blowing out..you need a min of 12" @same cfm going in....I have a tent, your house is the same concept...I use passive air flow for the "in" with four times the intakes, with a house id use less unless you dont mind the heat/air bill...=)

I realize this thread is a year old however i have the exact same issue.What did you do to solve the problem?I have a room in my basement split in half which houses the veg and flower room.I have an 8" 750cfm exhaust fan in the flower room which exhausts the air outside(Its on a speed controller slowed to about half).There are passive intakes between the veg and flower room.In the veg room i have a 6" 400cfm(not sure on exact cfm)pulling air from the second floor and into the grow.My problem is the neg pressure in my house pulling air down the furnace/hot water heater exhaust chimney.PLEASE HELP ME FIGURE THIS OUT!! Can i completely seal my rooms with no intake or exhaust and just use co2??

medgrow6006 said:

I realize this thread is a year old however i have the exact same issue.What did you do to solve the problem?I have a room in my basement split in half which houses the veg and flower room.I have an 8" 750cfm exhaust fan in the flower room which exhausts the air outside(Its on a speed controller slowed to about half).There are passive intakes between the veg and flower room.In the veg room i have a 6" 400cfm(not sure on exact cfm)pulling air from the second floor and into the grow.My problem is the neg pressure in my house pulling air down the furnace/hot water heater exhaust chimney.PLEASE HELP ME FIGURE THIS OUT!! Can i completely seal my rooms with no intake or exhaust and just use co2??

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Yes you can but you would still need to air cool your lights.

Look into "Texas style" growing.

Sealed rooms with air cooled hoods, AC and Co2. The filter and fan sit inside the grow room filtering the air within the room and exhausting back into the room.

J

dont exhaust your air outside. exhaust back ino your house. or pull air in from outside into your growrooms.

No, you have to have Oxygen too. The roots take it in, and the more there is, is better. That's why Aeroponics works so well. That explosive root development is the result of the additional Oxygen present in the chamber where the roots grow to, as opposed to soil which contains very little.
Another problem with the first guy's post was that he mentioned that the two fans were "back-to-back". This changes the CFM's of each fan, doubled. So that say 400 + 400 CFM's doesn't equal 800 CFM, rather it equals 1600 CFM's. They "potentiate" each other. He might have done "OK" if that was changed back to single outlets and not back-to-back. Just a thought...

shizz said:

dont exhaust your air outside. exhaust back into your house. or pull air in from outside into your growrooms.

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This is correct