Empty grow room 86f - way to hot?

Hello.

Still trying to figure out how to do this grow as I have a problem with heat.

86f is measured inside an empty grow tent and the outside temp is 77f, thats already a problem by itself but I cant do anything about it. Temperature inside is measured in the middle of the tent, halfway up to the lights under a piece of paper covering the termostate.

Will this be a huge problem? How does filling the tent up affect temp? Its a stealth grow so "just give it a go" doesnt really work.

Ive come around people saying like "plants will soak heat" and watering the soil will lower it even further.

Those folks are correct in that once you fill the room with plants, your temps will drop slightly, RH will go up. But that's typically a couple of degrees, not 10 degrees. You're starting high so you'll want to drop that a bit by exhausting more, bringing in cooler air, or both.

86 is too hot. plants will grow, but they'll suffer for it, and you won't get close to the best yield or quality they could produce. you want your temps to be under 80 if at all possible, if you're using h.i.d. lights, like metal halide or high pressure sodium. you can go up to about 85 if you're using leds, as they produce less ir heat and will not heat up the leaf surface as much as h.i.d.

Im using 5 vero 18s is a diy led light with 75w, its a mini/micro grow which need to be stealth.

The problem is the space I have to have the grow in. Its more or less my only option. I have been look at different solutions to ventilation but most Ive looked at, even in the 100$ price range is sounding like turbines without a big silencer on it. With a humidifier Im down to 84f and 50% RH. Its summer now so not going below like 75f except during the night.

buy a 6 inch fan and run it at 1/2, or even 1/3 speed, it will be much quieter than a 4 inch running wide open. not going to say its silent, but it's at least a 50% noise reduction, probably more.
if you put the fan in a box with a couple of holes cut out for the exhaust hose, and pack some old clothes or towels around the fan in the box, that'll cut that noise by another 50%

I have to look into that. Right now im using a diy charcoal and pc fan because I read somewhere in a "guide" that venting to fast would put stress on the plants. I guess heat is a much bigger stress and have to prioritize it.

you don't have to "vent too fast"...some fans come with speed controllers, or you can buy one and plug the fan into it. you just have to run it fast enough to drop the temps under 80.
you could also run your lights at night, when there are less people around to hear the fan to begin with, and the temps are a little cooler.

Yeah running lights on at night is the main thing you can do. Having them off for 8 hours in the hottest part of the day.

Those PC fans dont do much and dont handle resistance of carbon pads/filters too good.
But you could try and double up on the fans to suck out more heat quicker.

Whats your grow footprint?

This is the part at youre going to laugh.

Its only a very small space, 1.64x1.64x3.2.
Thats why Im running the light so low (per unit) that I can get the canopy really close without burning it.

Ive actually tried the filter with a various things to chech odur and its fine. With only around 9 cft to work with I didnt dare going the inline route.

However it doesnt really matter if I turn that fan way up, its one of the Noctua industrial fans with alot higher static pressure. But what does this matten when it doesnt work right

I grow in temps higher than that over summer.

Is it ideal? Probably not. But it is certainly doable.

dtrip said:

This is the part at youre going to laugh.

Its only a very small space, 1.64x1.64x3.2.
Thats why Im running the light so low (per unit) that I can get the canopy really close without burning it.

Ive actually tried the filter with a various things to chech odur and its fine. With only around 9 cft to work with I didnt dare going the inline route.

However it doesnt really matter if I turn that fan way up, its one of the Noctua industrial fans with alot higher static pressure. But what does this matten when it doesnt work right

Click to expand...

Nothing wrong with a micro grow, providing you can get it dialled in.
I asked about the footprint in case you were running higher wattage than needed so we could look at dimming it down.
But sounds like your bang on for that space.

As for the fan, they work when not dealing with resistance. But I have seen hundreds of guys make homemade carbon filters with them for micro grows and not seen many that work well enough or at all.
But that said, I would do a smoke test with it so you can visually see if its drawing air from the cab. A joint or a joss stick will do.
If its drawing anything at all though then double up on fans. Or try adding one fan either side of the filter to see if it helps overcome the resistance.

Next we need to make sure the hot air if its going out, goes far away from the intake.

Im going to try that out.

Going with a big vortex fan would be my last option because of the small space. My calculations suggest that ideal ventilation would be around 5m3/h and even the 100mm fans are way above 100m3/h.

To make one of those work I would have to use 1m ducting to a filter inside the tent and a silencer on the outside but even if its dialed way down I dont know if it gets even close to the 5m3/h.

I think you have probably worked out your air flow based on air exchange rate, which is more to do with maintaining co2 levels than it is maintaining temps.

Try using this instead. It takes your wattage and ambient temp and desired temp rise into consideration. It doesn't take resistance from filters and duct into consideration though, but its useful to be able to see what m3/h you would need to be x degrees above ambient. It gives a vastly different figure than 5m3/h.

Thanks for the help. Really appreciate it!

How many exchanges per minute do I dare? I guess an inch or two layer with carbon should really help pushing the numbers down.

The pc-filters works I guess, with everything closed I clearly see water mists from the humidifier getting sucked into the ports at the bottom of the tent.

I will investigate some bigger fans and silencers, or making a box to isolate the sound like a suggestion I got here.

This is becoming a lot harder than what I thought if I dont want to get bushweed...

you want your exhaust to be out of a top vent, hot air rises, use the bottom vents as passive intakes and vent the hot air out of the highest vent you have

So this is starting to piss me off. I think its a problem with radiant heat and air circulation inside the tent.

Just got myself a 100mm inline, fan control and ducting and I have the same temperature. Sure, I added more carbon for safety measure but instead of venting right up outside the tent I ducted it out of the room that the tent is inside.

If I put the sensor just past the intake the temp is 79f and in the middle its 86f...

put the thermometer just above the light/shadow line on your tent wall. that's as close to canopy temps as you can get

Air movement is the key , I grow in a wind tunnel

dtrip said:

So this is starting to piss me off. I think its a problem with radiant heat and air circulation inside the tent.

Just got myself a 100mm inline, fan control and ducting and I have the same temperature. Sure, I added more carbon for safety measure but instead of venting right up outside the tent I ducted it out of the room that the tent is inside.

If I put the sensor just past the intake the temp is 79f and in the middle its 86f...

Click to expand...

A picture of the space and what your using would help.

This is my set up. Ignore the plants. Top down: Carbon filter, 6 inch ducting. Air cooled sealed hood, fans and down the bottom two passive intakes. Exhaust fan is outside the tent.


In summer I can see 40s C in the tent (104F's) as I grow in an uninsulated tent.
This bud was grown last summer and saw 32-33c (89F). ( I think its the middle plant in the above pic btw)


You can clearly see the heat stress. But its certainly doable.

Lucky Luke said:

A picture of the space and what your using would help.

This is my set up. Ignore the plants. Top down: Carbon filter, 6 inch ducting. Air cooled sealed hood, fans and down the bottom two passive intakes. Exhaust fan is outside the tent.

View attachment 4163679
In summer I can see 40s C in the tent (104F's) as I grow in an uninsulated tent.
This bud was grown last summer and saw 32-33c (89F). ( I think its the middle plant in the above pic btw)
View attachment 4163682

You can clearly see the heat stress. But its certainly doable.

Click to expand...

I’m a newb on heat stress...what are the indicators in that last picture