Makeup air

[Cloud Surfer]

Just curious if anyone has had issues when exhausting from inside to outside? If so, what was your fix?

Quick info:

I have a 5x9 tent that I was planning to setup in my basement. The tent itself would be in a 10x25 room (separate from the rest of the basement). Ambient temps range anywhere from mid 50s in the winter to upper 60s in the summer. The plan was to exhaust the tent directly out of the window and just use a passive intake.

My concern is causing my fuel oil furnace to backdraft into the house. My father inlaw died from C0 poisoning so this is not something I want to chance. Current exhaust fan is rated for 440cfm which is a lot of air to be extracting from the house.

If I had a new high efficiency furnace with its own combustion air supply I wouldn't worry so much. However, just last week I had a bathroom exhaust fan running (we'll say 125cfm) and the range hood running(we'll say 400cfm) and noticed that I was indeed starting to get some backdrafting.

I'm worried that if I have a makeup air ducted into the basement, then I would have uncontrolled freezing air in the winter / hot air in the summer pooring into the basement disrupting the ambient temps. This obviously would add a lot of stress to the heating and cooling system, not to mention my air for the passive intake might to be suitable for cooling the tent in the summer since ambient temps would obviously be higher.

Not sure if I could get away with just exhausting back into the room the tent is in or even out into the larger open room in the basement. I'm also not too keen on introducing the high humidity levels back into the basement.

Sorry for the long post, and any help would be greatly appreciated.

 

[Renfro]

My concern is causing my fuel oil furnace to backdraft into the house.

A CO alarm is advisable of course.

Not sure if I could get away with just exhausting back into the room the tent is in or even out into the larger open room in the basement. I'm also not too keen on introducing the high humidity levels back into the basement.

If you indeed do have back drafting issues with your appliances then you may find the simplest solution is to run sealed CO2, using the room your tent is in as a lung room. In this case a dehumidifier and AC unit will be required.

If you wanted to get air from outside as makeup air then you can install a damper on the intake that will open when the temperature controller dictates. This way it's not letting air in all the time.

 

[Cloud Surfer]

I figured running a sealed room might be my only option. Unfortunately funds don't allow for a mini split at the moment.

When you say use the room the tent is in as a lung room, what would this setup look like?

Exhausting the heat and humidity from the tent back into the room the tent is in, then using an a/c and dehumidifier to condition the air only to be drawn back into the tent through the passive intake? If so, I guess there's no point in using the tent and I'd be better off just using the room itself?

Sorry if these questions seem redundant or basic. After reading how people just exhaust their tents straight outside without mentioning backdrafting/ makeup air issues I thought I had all my bases covered. Then the minor backdrafting caused by my upstairs exhaust fans changed everything.

 

[Oldreefer]

My grow area isn't in a basement but I exhaust into a hot water flue...controlled by temp/hum ac infinity T4...filtered passive intake until temps activate inkbird controlled intake fan for outside makeup. A properly setup fan system can nullify most problems.

 

[Cloud Surfer]

This is the controller I have.


My thoughts were this would be enough to control day/night temps and proper air exchange. Once proper temps were achieved the exhaust fan would idle at 37%, still bringing in some new air.

For now I only have one Sun Systems 630lec. The plan was to go through the normal growing pains while dialing in the system then possibly adding another 630 or some led lighting. I've never implemented the scrog technique which is why I didn't want to go full blast from the start. The basement has 7' ceilings. I have 2 4x4 heavy duty metal screens with 3" square openings to use. Thoughts were to use a 4x8 footprint in the 5x9 tent allowing me some room to maneuver around. I have the high cfm kit to prevent the walls from sucking in too far, 2 hygrometers to measure temps and humidity above and below canopy level, 2 12" oscillating fans for circulation, 6" inline hurricane with a 6"x24" presh carbon filter, and a large dehumidifier to control the intake air.

Not sure how having another fan hooked up to bring outside air for makeup would work... temps get too cold in the winter and too hot in the summer unless I'm missing something.

I'm by no means an expert and not doing this to make money. Just an avid grower looking to produce some good smoke for my wife and I. I really liked the idea of a tent, as it could have its own mini climate zone and I could use it for drying the plants and then sterilizing the environment before the next cycle.

I've setup heating and cooling systems from simple mini splits all the way up to grows using 10 5ton units and crazy duct work for cooling. I was really just hoping to have a fairly simple system for some hobby growing.

I thought I had most of it covered but somehow forgot the fact that in a house you need to account for whatever air gets exhausted should be replaced.

Thanks for the responses fellas, looks like I'm back to the drawing board.

 

[Bookush34]

I just put a outside air intake into the room. No vacuum effect on the house, just that room

Without that vent my wood stove would be a pain to get to draft when starting a fire.

 

[Cloud Surfer]

I just put a outside air intake into the room. No vacuum effect on the house, just that room

Without that vent my wood stove would be a pain to get to draft when starting a fire.

If you don't mind me asking, what state are you in? Do you have any problems with incoming air temps and heating/cooling the tent?

I'm in Michigan so the winters get cold and the summers can get quite warm. Just a little worried that the constant uncondtioned air dumping into the basement would have negative effects on the ambient air being used by the tent and the entire upstairs as well.

There's 1 window in the 25x10 room that the tent will be in. Would having an exhaust and intake from the same window be counterproductive (drawing back in the air being exhausted)? It's an old window so I planned on putting new block and mortar window in, leaving a 6" opening to directly attach the exhaust.

Would I be better off having the fresh air intake in the large portion of the basement? It has a window at the opposite end of the proposed grow room. This option might allow for the air to be somewhat conditioned before being drawn into the smaller room at the opposite end through a passthrough?

Would I be better off just exhausting out of the 25x10 room into the larger room, letting the dehumidifiers and supplies from the furnace somewhat recondition the air before being drawn back in? Not sure how much humidity to expect being dumped out of a packed 5x9 tent or how much heat from 2 630s. During the summer, I have a dehumidifier running in the basement 24/7 without any growing going on, so not too keen on introducing more humidity. However, this method would eliminate any backdrafting/negative pressure on the whole house and eliminate the constant flow of uncondtioned air into the house.

Lastly I know a mini split or small 1.5 ton furnace/ac would eliminate this whole hassle. I just don't have the funds for that and am trying to keep my electric costs down as low as possible. Really hoping to get this going soon. I've ran all new 110 to room and the 220 for the lighting. All walls and ceiling in the entire basement have been sanitized and will be getting painted/sealed soon. Just need to get this ventilation figured out and I should be ready to start.

 

[getogrow]

There's 1 window in the 25x10 room that the tent will be in. Would having an exhaust and intake from the same window be counterproductive (drawing back in the air being exhausted)? It's an old window so I planned on putting new block and mortar window in, leaving a 6" opening to directly attach the exhaust.

Would I be better off having the fresh air intake in the large portion of the basement? It has a window at the opposite end of the proposed grow room. This option might allow for the air to be somewhat conditioned before being drawn into the smaller room at the opposite end through a passthrough?

The first way you mentioned can work just fine if the intake is ran to the other side of the tent/room before being let out......then it flows right back out the outtake on the oppisite side of the tent/room. This eliminates the backdraft worry.

the second way you mention is fine too, use the other widow for intake. Same principle.

Now at this point your normal ambient temps are fucked but you dont have to worry about backdraft. 5x9 with a full canopy is going to be a LOT of humidity in the tent itself. So that will need pumped out no matter what. On regular days where your at , it wont drastically change the whole basement , so in theory , your humidifier wont run a shitton more then it already does.
A rough guess on a 5x9 is about a gallon a day to remove.

In my opinion , a mini split is going to make it to where you have to use co2. That may or may not be cheaper then running a regular ac and possibly a space heater. (probably not much heat needed though)

 

[Bookush34]

If you don't mind me asking, what state are you in? Do you have any problems with incoming air temps and heating/cooling the tent?

I'm in Michigan so the winters get cold and the summers can get quite warm. Just a little worried that the constant uncondtioned air dumping into the basement would have negative effects on the ambient air being used by the tent and the entire upstairs as well.

There's 1 window in the 25x10 room that the tent will be in. Would having an exhaust and intake from the same window be counterproductive (drawing back in the air being exhausted)? It's an old window so I planned on putting new block and mortar window in, leaving a 6" opening to directly attach the exhaust.

Would I be better off having the fresh air intake in the large portion of the basement? It has a window at the opposite end of the proposed grow room. This option might allow for the air to be somewhat conditioned before being drawn into the smaller room at the opposite end through a passthrough?

Would I be better off just exhausting out of the 25x10 room into the larger room, letting the dehumidifiers and supplies from the furnace somewhat recondition the air before being drawn back in? Not sure how much humidity to expect being dumped out of a packed 5x9 tent or how much heat from 2 630s. During the summer, I have a dehumidifier running in the basement 24/7 without any growing going on, so not too keen on introducing more humidity. However, this method would eliminate any backdrafting/negative pressure on the whole house and eliminate the constant flow of uncondtioned air into the house.

Lastly I know a mini split or small 1.5 ton furnace/ac would eliminate this whole hassle. I just don't have the funds for that and am trying to keep my electric costs down as low as possible. Really hoping to get this going soon. I've ran all new 110 to room and the 220 for the lighting. All walls and ceiling in the entire basement have been sanitized and will be getting painted/sealed soon. Just need to get this ventilation figured out and I should be ready to start.

I am in Canada we get cold winters and warm summers.

in the summer I have the 4” intake to the room wide open. Well any weather above freezing really.
In the winter I put a duct plug in the 4” with a few hole in it to slow the cold winter air. But when it gets lower then -20c I notice the tent has a hard time getting to temperature. So I close the vent off completely

 

[Cloud Surfer]

Thanks for the feedback getogrow & Bookush34. Not sure how to like your posts or I would.

Guess I'll try connecting the fresh air intake in the larger room's window on the NE side of the basement allowing it to be somewhat conditioned before it hits the grow room on the SW side of the basement. Any thoughts on if a 4" fresh air would suffice or should I make it 6"? Planning on using insulated flexible duct and having it go to the floor then back up a couple feet, creating a trap like cavity so only the amount of air needed to equalize the negative pressure in the house will be pulled.

Lastly, would dust shroom covers be suitable for the fresh air intake into the basement and the passive intakes on the tent? Not sure if these are meant to be used on ducting with fans? I like the idea of them being hepa but not sure if enough air would flow through them without fans? I know I can use some cheap non pleated furnace filters but I would much rather use the best filters possible while still allowing adequate air flow.

 

[getogrow]

You might need to go with a 6" or 8" passive intake with a filter like that. The restriction of the filter may cause unwanted air coming from other less restricted places. If its sealed up enough for that to be the only intake , then sure a 4" with a nice filter will be enough.

 

[redi jedi]

Set it up as normal, put a CO detector in the grow room. Even if you do create enough negative to pull exhaust out of the furnace its still going outside. Bet ya 100 bucks your being paro!

 

[sf_frankie]

I would run a larger intake if I were you. Before I sealed my room I tried a 4” intake with a 6” exhaust and it didn’t work out to well. The pressure on the room was so fucked up that it would hurt your ears. I’d imagine that effect would be problematic in a tent.

 

[Cloud Surfer]

You might need to go with a 6" or 8" passive intake with a filter like that. The restriction of the filter may cause unwanted air coming from other less restricted places. If its sealed up enough for that to be the only intake , then sure a 4" with a nice filter will be enough.

Guess I'll try a 6" with some type of furnace filter to help filter the outside air before entering the basement. The house is old so I'm sure some air would be drawn from other places which would be ok, but I don't want anything too restrictive to where it's pulling from the furnace exhaust.

Set it up as normal, put a CO detector in the grow room. Even if you do create enough negative to pull exhaust out of the furnace its still going outside. Bet ya 100 bucks your being paro!

I have C0 detectors upstairs and downstairs. I am the type to over think things a bit, but I don't think this is one of them. When I first moved in I ran the whole house attic fan with a cpl windows open and didn't realize the furnace wasn't turned off. Less than 5 mins of runtime filled the basement with so much exhaust that you couldn't see and you could literally taste the fumes/haze upstairs. I'm sure my 6" exhaust would be pulling close to if not more than my measly bathroom fan and old kitchen range hood... with both of those running and the furnace, I started getting backdraft (just nowhere near the amount from the attic fan) which is what started my concerns. Trust me, I don't want the uncondtioned air coming in and I would gladly lose $100 on this bet of paranoia, but I don't think I'd lose. Thanks for the response though.

I would run a larger intake if I were you. Before I sealed my room I tried a 4” intake with a 6” exhaust and it didn’t work out to well. The pressure on the room was so fucked up that it would hurt your ears. I’d imagine that effect would be problematic in a tent.

The whole basement/house isn't sealed the best as it is an older house.. which is why I was surprised by the backdrafting created by the upstairs fans. The room the tent will be in will have 2 6"x10" passthroughs to pull air from the larger room in the basement. As for the tent itself I was planning on 2 6" 90s for passive intake (twice the amount of the exhaust) with a dust shroom on each. If these filters are that restrictive to where they'd need intake fans installed then I'll just have to settle for cheaper/less filtration filters.

Just wasn't sure how restrictive the dust shrooms are. They don't appear to be too cheap so not trying to waste unnecessary money.

Sorry for the rambling and thank you all. This site is filled with endless info. Not sure why I can't "like" your posts but they are greatly appreciated.

 

[getogrow]

I hate setting up rooms. too much thinking involved.
If your only goal is to eleminate the furnace backdraft , you could use a small active intake to relief some of the pressure. You could go overkill on the passive intakes and use two or 3 of them. Slap your filter on high and see what were working with.
One of the main reasons we use a room that is negative pressure is to keep the smell contained. Other then that a lil positive pressure wont hurt the setup.

 

[redi jedi]

Guess I'll try a 6" with some type of furnace filter to help filter the outside air before entering the basement. The house is old so I'm sure some air would be drawn from other places which would be ok, but I don't want anything too restrictive to where it's pulling from the furnace exhaust.



I have C0 detectors upstairs and downstairs. I am the type to over think things a bit, but I don't think this is one of them. When I first moved in I ran the whole house attic fan with a cpl windows open and didn't realize the furnace wasn't turned off. Less than 5 mins of runtime filled the basement with so much exhaust that you couldn't see and you could literally taste the fumes/haze upstairs. I'm sure my 6" exhaust would be pulling close to if not more than my measly bathroom fan and old kitchen range hood... with both of those running and the furnace, I started getting backdraft (just nowhere near the amount from the attic fan) which is what started my concerns. Trust me, I don't want the uncondtioned air coming in and I would gladly lose $100 on this bet of paranoia, but I don't think I'd lose. Thanks for the response though.



The whole basement/house isn't sealed the best as it is an older house.. which is why I was surprised by the backdrafting created by the upstairs fans. The room the tent will be in will have 2 6"x10" passthroughs to pull air from the larger room in the basement. As for the tent itself I was planning on 2 6" 90s for passive intake (twice the amount of the exhaust) with a dust shroom on each. If these filters are that restrictive to where they'd need intake fans installed then I'll just have to settle for cheaper/less filtration filters.

Just wasn't sure how restrictive the dust shrooms are. They don't appear to be too cheap so not trying to waste unnecessary money.

Sorry for the rambling and thank you all. This site is filled with endless info. Not sure why I can't "like" your posts but they are greatly appreciated.

Have you had the chimney inspected or cleaned lately? How about the furnace? Sounds like you got a bigger problem...sorry to flare the paranoia.
A friend of mine has an old home that is oil heated, long story short, they added a length of stove pipe to the chimney and solved his issues.

 

[redi jedi]

I hate setting up rooms. too much thinking involved.
If your only goal is to eleminate the furnace backdraft , you could use a small active intake to relief some of the pressure. You could go overkill on the passive intakes and use two or 3 of them. Slap your filter on high and see what were working with.
One of the main reasons we use a room that is negative pressure is to keep the smell contained. Other then that a lil positive pressure wont hurt the setup.

Negative pressure also brings in CO2. You dont want a positive pressure grow room.

 

[getogrow]

Negative pressure also brings in CO2. You dont want a positive pressure grow room.

In this case, the positive pressure would be caused by the fresh air/co2 coming in. I cant see an issue with it other then its not our "norm"

 

[redi jedi]

In this case, the positive pressure would be caused by the fresh air/co2 coming in. I cant see an issue with it other then its not our "norm"

Where is the fresh air coming from? Pulling from another room creates the same problem. Fresh air from outside and you lose climate control and were is the odor and humidity going?

 

[ikushy420]

not a pro or cant advise you anything that would really help help or solve ur backdraft problem but. As someone stated get a Co Alarm either way. hope you resolve ur issue ma dude .