High temp and low humidity problems in my tents

By venting your tents outside your house you are putting your entire house under negative pressure. To balance the pressure differential, outside air is being pulled into your house through chimneys, cracks, around doors, etc. (At least it was for me when I held a lighter up to the gaps around my exterior doors I could see the flame being blown by the incoming air).

What is your outdoor climate like? Could the unconditioned air potentially being pulled in by your fans be a source for your problems?

I don't vent outside anymore and have had an easier time controlling my climate since I changed. Just a stab in the dark.

My outdoor climate is extremely hot and dry. These past few weeks have been in excess of 105*F with humidity in the low 20 percent.

I thought venting outside would help with my heat issues. I can try venting back into the tent room to see if that helps.

Relic79 said:

By venting your tents outside your house you are putting your entire house under negative pressure. To balance the pressure differential, outside air is being pulled into your house through chimneys, cracks, around doors, etc. (At least it was for me when I held a lighter up to the gaps around my exterior doors I could see the flame being blown by the incoming air).

What is your outdoor climate like? Could the unconditioned air potentially being pulled in by your fans be a source for your problems?

I don't vent outside anymore and have had an easier time controlling my climate since I changed. Just a stab in the dark.

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True, I vent into the room but then you have to look at buying a big dehumidifier depending on where you live

illmatik said:

My outdoor climate is extremely hot and dry. These past few weeks have been in excess of 105*F with humidity in the low 20 percent.

I thought venting outside would help with my heat issues. I can try venting back into the tent room to see if that helps.

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You will get your humidity closer that way. Most economical in your case of hot and dry is a swamp cooler you can do yourself. An evaporative humidifier does the same thing cooling down the air a few degrees.

I've vented the tent back into the room for a few hours. Temps are up 2 degrees and climbing. RH has went up a few percent but not sure if it's worth the temp increase

illmatik said:

I've vented the tent back into the room for a few hours. Temps are up 2 degrees and climbing. RH has went up a few percent but not sure if it's worth the temp increase

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Are you able to vent into a different room? Maybe a cold air return?

With it venting back into the house, you can take other steps to correct the environment without dumping the air out the window, and since the outdoor air should not be rushing in, your humidity should be more controllable.

If you exhaust outside you will constantly be fighting the incoming outdoor air, and will be dumping any conditioned air right out the window. Humidifiers and other devices will need to be oversized to have any substantial impact.

Think of your entire house as your lung room, you need to seal it, cool it, and humidify or dehumidify it enough so that the air sucked into the tent keeps things in the target range.

However, if you vent into the same room, heat will accumulate.

Relic79 said:

Are you able to vent into a different room? Maybe a cold air return?

With it venting back into the house, you can take other steps to correct the environment without dumping the air out the window, and since the outdoor air should not be rushing in, your humidity should be more controllable.

If you exhaust outside you will constantly be fighting the incoming outdoor air, and will be dumping any conditioned air right out the window. Humidifiers and other devices will need to be oversized to have any substantial impact.

Think of your entire house as your lung room, you need to seal it, cool it, and humidify or dehumidify it enough so that the air sucked into the tent keeps things in the target range.

However, if you vent into the same room, heat will accumulate.

Click to expand...

I've been thinking hard about this one and I'm not sure if there's a practical way to vent into another room in the house. Even if I were to cut into the walls to exhaust it into another room, I feel like I'd be creating another problem. My central A/C is already working overtime all day long to keep us cool in 105+ heat. I'd hate for it to have to work even harder to cool off hot and humid air coming from the tents.

I think I may just have to make due with exhausting out of the house. The room does have a lot of negative air pressure but I can feel a ton of air coming from through bedroom door, so hopefully most of the fresh air is coming from other areas of the house rather than outside. I'm going to work on insulating the window vents where the exhaust is going to minimize hot/dry air being pulled into the room.

In other news, my plants were pissed off because I had went too long without refilling my res and the pH was swinging. I thought VPD was the culprit, but I'm hoping my plants can thrive in the conditions that I'm stuck with.

Fair enough. I am just not sure I've adequately explained my thought on this though.

You say you'd hate for your ac to have to work hard at cooling the lights, the thing is, normally a house is a closed system. Your a/c works by recirculating the air in the house and bringing it down to your set point over time by cooling the same air over and over.

When you exaust your tents outside your house you are turning your house into an open system. Let's say you are venting a total of 600cfm out your window. That means 600cfm of air needs to come back into the house from outside to equalize the pressure. Doesn't matter how much you seal up cracks. You are creating a vacuum that can't be sustained by a house and air will come in from outside somewhere, it just has to.

The question becomes what way is your a/c working harder. To cool a dehumidify the 84 degree air from your tent for 12 to 18 hours, or the 105 degree air from outside being pulled in at 600cfm (fictional CFM number for example)?

If you vent outside you will have an equivalent amount of air from outside the house being pulled back in, otherwise your fan would stop working when it could no longer overcome the vacuum.

Sorry, not trying to argue or convince you, just wanted to make sure I was completely clear as to the problem I see. I truly think venting back inside while still a problem, will be easier to solve. An extra window a/c unit in the room for example would knock the temp and humidity down and keep your central air from working overtime.

I'll leave it at that I think. Hope some of this has helped! While my outside temps are not as high (low to mid 90s) I'm fighting the same battle, and made progress only when I started venting inside. Window a/c is probably my next step.

Water evaporation pulls heat from the air, you can make effective use of evaporative cooling to simply solve your problem, seen my large unit lower by 5 degrees.

Relic79 mentioned cold air return, you should make sure adjacent room's air circulation is beneficial to your grow by having a floor and doorframe fans to promote high and low air movement throughout.