Help with Temp/humidity & VPD guidelines for 1st indoor grow

Hi,
I have a few weeks left to prepare my set-up before closing doors and going travelling. On my return I'd like to be able to just wipe the room down and get straight into growing.

So I'm pretty much ready to give my new tent a test run later today/tonight. Please correct me if I'm wrong but I believe I should be aiming to stay around these temp & humidity figures during the different growing phases;

Seedling stage: 28°C/75%rh (0.59kpa)
Vegetative stage: 28°C/60%rh (1kpa)
Flowering stage: 26°C/45-50%rh (1.39kpa)

Can I please confirm that temp readings should be taken from canopy level? I am awaiting a infra-red thermometer to check leaf temps to plug figures into this chart as a VPD guidance; https://vpdchart.com/

I will play with light height and power level to check the Lux readings to figure out my ppfd, which I believe should be;

Seedling: 100-300 umol/m2/s
Vegetative stage: 400-600 umol/m2/s
Flowering stage: 800-1000 umol/m2/s

Couple extra questions;
-What is the average temp difference between your grow tent and the room tent is in? and tent temp difference to leaf temp?
-Is there a good way to check air pathway and exchange rates in the tent? I blew a couple bongs through air intake but it's gone to quick to track.

Anyway, I appreciate any help and I understand conditions will change once introducing the growing medium, plants and water so surely many tweaks needed again once actually growing but I am still happy to have a play around now while there's no plants in the way. Cheers.

Cheers, appreciate the tips gents haha

Got the tent dialled in well enough I think now to wait until I start growing. Trialled 3/4 different stages this afternoon, and all conditions are pretty close to the numbers I mentioned above. I've atleast got something to go off. Light was 20/21" from where top of growing medium will be for all tests.


Anyway, everything looks like I should be right...need to remember right now is still winter though, so unsure how the room will look come summer and rainy season and once dirt and water goes in and plants start growing. Hopefully much better than outdoors if I'm lucky. Cheers.

i just didnt understand the question well enough. so you will not leave plants to grow in there before going travelling. the tent will be empty and you are just trying out an empty tent? is this correct? because if so, it will be a very different thing with plants going through gallons of water each day in your tent.

crimsonecho said:

i just didnt understand the question well enough. so you will not leave plants to grow in there before going travelling. the tent will be empty and you are just trying out an empty tent? is this correct? because if so, it will be a very different thing with plants going through gallons of water each day in your tent.

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My question was just asking how everything looks, I've never grown indoors so was just checking if I was on the right track with regards to temp, humidity, ppfd etc for each stage of the growing cycle.

Travelling for 3months so yeah definitely not going to be any plants in there before or during my holiday, I'm just getting everything worked out so I'm ready to go once back home, instead of chasing up extension cords, fans, lights etc. Plus it has given me a fun hobby the last week tinkering with it all too.

Yes, hopefully it will make things a hell of a lot easier getting that humidity up with a few plants in there haha, won't need to use the humidifier to bump up rh like I had to yesterday I'm sure. Cheers.

What gear are you using to control climate in your tent? To get to the vpd levels you chose, you are more than likely gonna need humidifiers, dehumidifiers and an AC system at a minimum. A sealed room would also help but then you need to add co² aswell, the price of all that gets a little crazy but if you want the type control you are suggesting you want, it's what will be required.

King Avitas said:

What gear are you using to control climate in your tent? To get to the vpd levels you chose, you are more than likely gonna need humidifiers, dehumidifiers and an AC system at a minimum. A sealed room would also help but then you need to add co² aswell, the price of all that gets a little crazy but if you want the type control you are suggesting you want, it's what will be required.

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Hi, thanks for the comment. Initially I couldn't control anything, but I then added another intake and exhaust with a couple voltage regulators and it's a much different climate in there now, actually able to dial in to different vpd levels quite easily without any plants inside. My first test I couldn't lower the temp inside or anything so really glad I got those extra fans.

Yes to get to those 3 different climates the other day (seedling stage, veg, flower) I used either the humidifier, dehumidifier & AC . I have a feeling the humidifier may not be needed once soil and water goes in the tent though and the battle will be with the humidity and temperatures. Will need to use AC for flower I'm pretty much certain.

But can I please ask, are my figures I've researched about ppfd, vpd, temp etc. On the right track or nowhere close...honestly I was able to find information which details every temperature and humidity being recommended which is ridiculous, I thought the numbers I put in first comment would be a good number to try aim for.
Anyway no stress, like the old man said, don't be too worried about the information online being inconsistent or all over the place, instead he'll show me his way and I can go from there.
The room is really comfortable now, both below and above the light whereas before I don't think the air was exchanging well. I won't go down the co² path, as you say expensive etc. This will be enough to give me a hobby and work my way to producing some quality meds for a fraction of the price...I hope haha. Cheers mate

Using an AC unit will make it considerably easier to dial things in as you don't really want to be relying on intake and exhaust vents as they will be making your tent match the conditions in the room your tent is in rather than the VPD you are trying to achieve inside the tent.

You will need a humidifier especially if you are looking for 75% humidity. The plants don't transpire much until they get fairly large so a humidifier will be an absolute must for most of the veg phase.

Once you are well into the flowering phase things will pretty much switch overnight and you will find that you need a dehumidifier or a big exhaust fan to get rid of the excessive humidity. When the stretch is done and the plants have some decent sized buds they will be transpiring heavily.

As for your parameters, personally I wouldn't shoot for anything lower than 0.8kPa. The 0.59kPa is liable to make it rain inside your tent if the outside of the tent is much cooler than the inside, things could condensate inside your tent at those levels.

The 1kPa for veg seems about right. And the 1.39kPa should work for late flower but achieving 45% humidity could be a stretch without a dehumidifier. Even in my sealed room with only 4 plants and a top of the line Quest dehumidifier, I have issues getting below 50% humidity.

Okay too easy, the AC unit is a decent system so happy to use as much as is required. Situated perfectly above the tent too, cools the room very efficiently for sure, just needed those fans to help get it moving through the tent better. Luckily the house is quite cool compared to other areas I've stayed around here atleast.
I have the two 6" exhausts plumbed into the roof so not exchanging back into the same room tent is in.

Lots of cool air being sucked through the small gap under the door into room and then through one of the 6" inlets on opposite side. Stockings on all ends. Unsure if that gap is a good thing or bad really though...

Good point, I didn't think about that to be honest, I thought possibly the soil and water would raise humidity enough as usually it's like 70%+ here but just incase I have been testing an 11L humidifier and it's a little beast, works great, hopefully it performs well when required if need to use it.

Okay, I do have a dehumidifier also, not as big as the humidifier, may need to revisit that if I make it to flower but atleast do have one and have tested it out, so slightly prepared.

Hmm I can see that happening as definitely room cooler than tent, but not a great deal of difference during seedling stage compared to when in flower.
I've played with the vpd chart and it looks like I need to run some high temperatures to get 0.8kpa during seedling stage if aiming for 75% humidity. Although if able to run 70% humidity instead that brings things back around that 29-30°c range for 0.8kpa. Will aim for that, what do you reckon?

I'd be happy if I could manage 50% come flower, will see if this one can do it, min setting is 45% and pulled room down pretty quickly to 50% when giving it a test run. Think it may not be cut out for the job but we'll see I guess, should work great in a smaller tent.

Sorry, I'm sure I misread about the AC unit, I now believe you meant a unit inside the tent.

Do those exhaust lines go outside or into an attic? Personally I would vent outside your house. Venting into the attic or any other inside room will cause mould.

King Avitas said:

Do those exhaust lines go outside or into an attic? Personally I would vent outside your house. Venting into the attic or any other inside room will cause mould.

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They just go into the ceiling, same as the bathroom fans. High roof with vents if that matters...I did want to plumb them up to one of the windows but not happy with that from outside.

Here's where they are in the ceiling, plenty of airflow it seems up there but maybe better off pulling them back down and sealing the door better then just venting into the room?

Thai Fox said:

Here's where they are in the ceiling, plenty of airflow it seems up there but maybe better off pulling them back down and sealing the door better then just venting into the room?
View attachment 5254334

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It depends on temps. If you're exhausting cooler air into a hot attic, it will be fine. If you're exhausting hot air into a freezing attic, you are setting yourself up for mold. Either way, your safest option is to vent to the outside.

MtRainDog said:

It depends on temps. If you're exhausting cooler air into a hot attic, it will be fine. If you're exhausting hot air into a freezing attic, you are setting yourself up for mold. Either way, your safest option is to vent to the outside.

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Attic would range from about 25-35°c
air exhausting from tent will be similar depending what stage they're in I guess

Here's the inside of the tent. Pretty much just waiting on 20gal pots and pans as got good advice from green machine that my 7gal aren't really big enough for my medium plans. Also have some tomato cages on the way as look like they'll suit what I'm after perfectly.

Awesome setup. Love the overkill. (Maybe more light though)

Marq1340 said:

Awesome setup. Love the overkill. (Maybe more light though)

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Thanks, can't wait to get in there and start growing. Possibly can add more lighting in the future or more than likely decrease tent size...Happy to give it a go though with 4 plants first. I really do like the amount of room to move around in there.

@green_machine_two9er the 20gal fabric pots arrived today and I must say they take a whole lot of dirt compared to those 7gal pots I originally had planned. Luckily had plenty of soil, was a big job mixing the rest of the amendments in yesterday! I still had enough leftover to fill two 7gal pots for a couple autos and kept another 100L brewing away to use for top dressing the 20gal pots. Glad you chimed in and mentioned those 7s aren't really big enough for living soil grows. All ready to rock and roll now. Really appreciate the help.

Looking clean and crisp! What is that a 10x 10 tent?