Dealing with low humidity in exhausted tents

[Sureshot2]

Alright so I'm looking for some input on raising the humidity in two 2x4 tents that are hovering in the mid 30% range. My problem is that with the house AC running so often during the hot summer weather the air is already on the drier side (45%), and even more dry down in the basement where the tents are. My current setup has a 6" fan pulling through an intake filter on the left tent, going through the light baffle and exhausted through a 6x18" carbon filter in the right. The negative pressure is balanced with the exhaust running between the low and medium ticks on the dial.

I have tried all the common tricks like spraying tent walls, hanging damp towels, trays on a heated mat and of course placing a humidifier in the first tent. None of these methods have resulted in much except for the humidifier which can raise the RH to around 45%, but that's still lower than I'd like for veg. On top of that, the humidifier has to be running on full blast to achieve this and thus needs to be refilled very frequently. At this point the only thing I can think of is getting a larger commercial type humidifier that hooks to a reservoir, but I was hoping to not have to spend $300 on a humidifier.

If anyone has any ideas I'm all ears, since I'd really like to get my VPD dialed in.

 

[ha·bit·u·al]

Might not be for you but this is how I control vpd in my tent. My air is pumped into the 4x4 tent the room is a lung, the fan is on a plug and play humidity/temp controler. I set the fan humidity @ vpd max for the steady temps I never see above 80. The passive exhaust vents into the room. I have a filter/fan scrubbing the room near the external exhaust vent that keeps everything at a negative pressure.
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[Sureshot2]

Might not be for you but this is how I control vpd in my tent. My air is pumped into the 4x4 tent the room is a lung, the fan is on a plug and play humidity/temp controler. I set the fan humidity @ vpd max for the steady temps I never see above 80. The passive exhaust vents into the room. I have a filter/fan scrubbing the room near the external exhaust vent that keeps everything at a negative pressure.
.

Hmm that could be something to consider. What temp/humidity controller do you use for that, and can it control multiple fans? Right now my temps stay around 75-80 fairly consistently.

 

[mauricem00]

Alright so I'm looking for some input on raising the humidity in two 2x4 tents that are hovering in the mid 30% range. My problem is that with the house AC running so often during the hot summer weather the air is already on the drier side (45%), and even more dry down in the basement where the tents are. My current setup has a 6" fan pulling through an intake filter on the left tent, going through the light baffle and exhausted through a 6x18" carbon filter in the right. The negative pressure is balanced with the exhaust running between the low and medium ticks on the dial.

I have tried all the common tricks like spraying tent walls, hanging damp towels, trays on a heated mat and of course placing a humidifier in the first tent. None of these methods have resulted in much except for the humidifier which can raise the RH to around 45%, but that's still lower than I'd like for veg. On top of that, the humidifier has to be running on full blast to achieve this and thus needs to be refilled very frequently. At this point the only thing I can think of is getting a larger commercial type humidifier that hooks to a reservoir, but I was hoping to not have to spend $300 on a humidifier.

If anyone has any ideas I'm all ears, since I'd really like to get my VPD dialed in.

have you considered using an evaporative cooler in your basement?in the high desert where I live humidity is around 10% and air temperatures can reach over 100 but an evaporative cooler keeps temperatures down and humidity up in my house combined with thin air at this altitude growing can be a bit of a challenge

 

[Sureshot2]

have you considered using an evaporative cooler in your basement?in the high desert where I live humidity is around 10% and air temperatures can reach over 100 but an evaporative cooler keeps temperatures down and humidity up in my house combined with thin air at this altitude growing can be a bit of a challenge

Unfortunately that probably wouldn't work well here since we are dealing with outside humidity of between 65-85% so the AC is on very often and removing a very large amount of water from the air, and there's not really any way to run the AC without it drying out the basement as well since there's several intakes down there.

 

[Abiqua]

Unfortunately that probably wouldn't work well here since we are dealing with outside humidity of between 65-85% so the AC is on very often and removing a very large amount of water from the air, and there's not really any way to run the AC without it drying out the basement as well since there's several intakes down there.

Bigger humidifier might be your only choice.....or you may be stuck routing your intake air from the outside thru a dehumidifier and then maybe capping inside when [if] temps get really cold....this is what I would do, take the humid air and reduce it partially.....
but I also use or have been recently using ultrasonic misters to up my RH for maintaining a good VPD.....even better with just a little simple hygrometer and relay to control it off and on....then provide a reservoir that will last a week or so between refills.....

 

[MJCanada]

Did I read your original post properly? You are pushing air but creating a negative pressure?

Anyway, if you are taking air into your room, clearly there has to be negative pressure to do so.

Put a duct on that, duct it into a reservoir and make the air pass by a wick(or multiple). As it passes by, it picks up moisture, and the wick will pull more moisture up from the reservoir.

This is a DIY type humidifier...

Think of this... but doing it with an enclosed reservoir controls the air flow so you can maximize the air going across the wick.

In this video the sponges are wicks... cut them into strips for more surface area = more water into air(fiddle with this principal to adjust as needed)

If you need to heat the air, heat the water.

You will be putting humidity in, just before the room... and if you exhaust into your HRV... you can minimize thermal loss (only pipe into your HRV if you know how to rebalance it!!! or you could kill your family with CO)

 

[Sureshot2]

Bigger humidifier might be your only choice.....or you may be stuck routing your intake air from the outside thru a dehumidifier and then maybe capping inside when [if] temps get really cold....this is what I would do, take the humid air and reduce it partially.....
but I also use or have been recently using ultrasonic misters to up my RH for maintaining a good VPD.....even better with just a little simple hygrometer and relay to control it off and on....then provide a reservoir that will last a week or so between refills.....

I think I'll look into a environment controller and try to modify my humidifier tank to hook up to a larger res so I don't have to fill it so often.

Did I read your original post properly? You are pushing air but creating a negative pressure?

Anyway, if you are taking air into your room, clearly there has to be negative pressure to do so.

Put a duct on that, duct it into a reservoir and make the air pass by a wick(or multiple). As it passes by, it picks up moisture, and the wick will pull more moisture up from the reservoir.

This is a DIY type humidifier...

Think of this... but doing it with an enclosed reservoir controls the air flow so you can maximize the air going across the wick.

In this video the sponges are wicks... cut them into strips for more surface area = more water into air(fiddle with this principal to adjust as needed)

If you need to heat the air, heat the water.

You will be putting humidity in, just before the room... and if you exhaust into your HRV... you can minimize thermal loss (only pipe into your HRV if you know how to rebalance it!!! or you could kill your family with CO)

Yes you read it correctly, I have two fans, an intake and an exhaust. The intake is pushing less air than the exhaust pulls. I went with this route because I wanted filtered intake air, and because I'm pulling through multiple tents (the clone tent also vents through this system).

 

[ha·bit·u·al]

I have a room, in that room is a grow tent. The tent is closed up 24/7! The room has an exhaust fan over a window that draws air from the house into the room and out the window (so the room is a negative pressure room) . For the tent I have a 4" fan and duct running on a humidity controller going into the tent, it only comes on @70% rh and turns off @65%. There is an open ended duct that the tent exhausts through when the fan pressurizes the tent. The plants are all that is needed to get RH up and I live in a 30% rh area. This also provides all the co2 my system can use. There is a can filter with a fan on top in the room running 24/7 that cleans all scent.

Its pretty basic lung room set up and no mold ever and no equipment in the tent.

 

[MJCanada]

I think I'll look into a environment controller and try to modify my humidifier tank to hook up to a larger res so I don't have to fill it so often.



Yes you read it correctly, I have two fans, an intake and an exhaust. The intake is pushing less air than the exhaust pulls. I went with this route because I wanted filtered intake air, and because I'm pulling through multiple tents (the clone tent also vents through this system).

You don't need multiple fans, just 1 strong enough to move the air.

You can filter without fans. I do it to mine.

My light baffle is a passive intake, and I have a filter on the outside intake... and one on the inside (overkill I'm sure). So long as the external fan has enough pull, you don't have to worry about balancing anything because it'll always be negative.


That being said, you can still do the DIY humidifier, duct from your intake fan into 2 $5 bins from Walmart... stand some sponges on end(so they go from floor to ceiling in your little box, and half fill with water. Put a passive intake on one side, and your ducting to your tent on the other side.

Add more sponges to increase the amount of humidity drawn in, and as I said, if this lowers your temps too much, just heat the resevior. Also, suggestion to use distilled water, or wash your res out every few fills(bateria grows, especially if you hit the water).

You can control your humidity, and some of your temps by doing this alone.... all mechanical/physics, no extra energy(few extra ticks up on the fan probably) needed.

 

[ha·bit·u·al]

@Sureshot2

this is the controler on outlet or humidity and one for temp

 

[Sureshot2]

You don't need multiple fans, just 1 strong enough to move the air.

You can filter without fans. I do it to mine.

My light baffle is a passive intake, and I have a filter on the outside intake... and one on the inside (overkill I'm sure). So long as the external fan has enough pull, you don't have to worry about balancing anything because it'll always be negative.


That being said, you can still do the DIY humidifier, duct from your intake fan into 2 $5 bins from Walmart... stand some sponges on end(so they go from floor to ceiling in your little box, and half fill with water. Put a passive intake on one side, and your ducting to your tent on the other side.

Add more sponges to increase the amount of humidity drawn in, and as I said, if this lowers your temps too much, just heat the resevior. Also, suggestion to use distilled water, or wash your res out every few fills(bateria grows, especially if you hit the water).

You can control your humidity, and some of your temps by doing this alone.... all mechanical/physics, no extra energy(few extra ticks up on the fan probably) needed.

I don't have the ability to filter or exhaust the room the tent is in so I have to strictly go through the tents. Using a 6" fan with carbon filter the negative pressure was far too extreme and hardly any air was making it through the filter , and since it goes through three linked tents the negative pressure progressively gets stronger without an intake fan. So in order to have a filtered intake and balanced negative pressure I opted for an intake fan and an exhaust fan that are each set to the appropriate speeds.

 

[Sureshot2]

@Sureshot2

this is the controler on outlet or humidity and one for temp

View attachment 3995625

Many thanks! I'll look that up.

 

[ANC]

Those Inkbird controllers are nice, they have done a few free giveaways on the planted aquarium site I belong to.

 

[Observe & Report]

Fabric pots...

 

[Sureshot2]

Fabric pots...

Not sure I understand how that will help? If an entire full scrog of plants transpiring in an RWDC isn't releasing enough moisture I don't see how this would be any better?

Those Inkbird controllers are nice, they have done a few free giveaways on the planted aquarium site I belong to.

Yeah they look nice and the price is not bad compared to the stuff you find at the hydro stores.

 

[MJCanada]

Fabric pots...

In a 2x3 room 2 2 gallon fabric pots upped my humidity by 5%.

 

[Observe & Report]

Not sure I understand how that will help? If an entire full scrog of plants transpiring in an RWDC isn't releasing enough moisture I don't see how this would be any better?

I didn't see what containers/medium you were growing in. However, most people do rdwc in containers that are similarly sized to pots of dirt or whatever. These have similar exposed surface area, which is the key in passive evaporation. Fabric pots have much larger surface area for evaporation. Flood and drain trays with big hunks of rockwool probably also have a lot more evaporation than rdwc pots.

Changing your whole growing style is extreme though. If your humidifier / fans blowing on trays of water (or res) isn't cutting it you probably need either to get a bigger humidifier or reduce your exhaust.

 

[Sureshot2]

I didn't see what containers/medium you were growing in. However, most people do rdwc in containers that are similarly sized to pots of dirt or whatever. These have similar exposed surface area, which is the key in passive evaporation. Fabric pots have much larger surface area for evaporation. Flood and drain trays with big hunks of rockwool probably also have a lot more evaporation than rdwc pots.

Changing your whole growing style is extreme though. If your humidifier / fans blowing on trays of water (or res) isn't cutting it you probably need either to get a bigger humidifier or reduce your exhaust.

Ah my bad, yeah switching over from the rdwc/uc system would he a huge task and a big loss of money. I've reduced my exhaust as much as possible so I'm looking into modifying the humidifier I have to hook up to a larger reservoir that way I can run it on high without filling it twice a day. I'll also probably get a controller to better regulate things.