Autos - Room temp vs Root temp?

[Bobcharlieeeee]

does anybody know the minimum room temperature for Autos, if i were to keep

the roots warm with heat matts at around 18c - 20c?

 

i have my intake from inside my house so at night the intake temps can drop to about 14c at night in the winter

 

ideally i dont want to have to add a oil radiator or anything, for space and for the running costs! 

[MindSoup]

Thats a bit low, ideally roots want to be at least low 20s up to about 28 (I aim for 24), anything below that and you'll slow them down a fair bit. Air Temps don't seem to he as crucial in my experience, if you're keeping your roots the right temperature the air will usually stay in the sweet spot as well. 

[DeltaMelter]

@Bobcharlieeeee You could also run your lights at night to offset the cold. Assuming your daytime house tempos are not 14C!

[Wacky Wardrobe]

If they're autos you could run them 24/7.

I did autos on 24/7 on my last run.

Just make sure to adjust lighting levels down to account for the increased DLI.

I didn't quite get that bit right and ended up with ridiculously squat dense plants.

[Should Know Betterer]

@Bobcharlieeeeealso depends on what light you're running, if you're using hps you'll get higher ambient temperatures but if you're running leds you may well need to supplement the ambient temps with a heat source of some kind

[Should Know Betterer]

@Bobcharlieeeeesorry man just had a look at what you're doing and I'd say you probably will need an additional heat source in a loft with leds, heat mats can only do so much for ambient temps, 14° will be too low for your plants, I run an oil rad inside a big box ducted to my tent, keeps costs down a bit as I'm only heating the box not the room, good luck with your set up man 

[Bobcharlieeeee]

@MindSoup perfect, i was just worried the ventilation will remove more heat than the heat matts give off to the ambient area, 

 

Some people seem to say ambient temp doesnt matter too much but others iv spoke to said it needs to be higher than 18-20c

[Bobcharlieeeee]

@DeltaMelter thats the plan mate! 24/7 LED

[Bobcharlieeeee]

@Should Know Bettererwhats the minimum ambient temp would you say? iv spoke to others who have suggested as long as roots are kept in range the plants should be happy.

[Should Know Betterer]

Personally I aim for around 27°ish , I'm not one of the science guys but I'm sure one of them would say something about optimum temps for transpiration to occur etc,  yeah I'd go with root temps would be the more crucial for good growth but ambient temps also play their part towards good healthy growth, and the heat from leds doesn't really cut it, you could always put your filter down at floor level to pull what little heat leds emit down through your plants

[MindSoup]

19 minutes ago, Bobcharlieeeee said:

@MindSoup perfect, i was just worried the ventilation will remove more heat than the heat matts give off to the ambient area, 

 

Some people seem to say ambient temp doesnt matter too much but others iv spoke to said it needs to be higher than 18-20c

 

If you keep your roots at 24/25 your air will rarely drop too low, my current run I've just had my temp probe in the soil set to 24 and completely ignored air temps and its been my best run yet.

Edited March 17, 2022 by MindSoup

[Bobcharlieeeee]

22 minutes ago, Should Know Betterer said:

Personally I aim for around 27°ish , I'm not one of the science guys but I'm sure one of them would say something about optimum temps for transpiration to occur etc,  yeah I'd go with root temps would be the more crucial for good growth but ambient temps also play their part towards good healthy growth, and the heat from leds doesn't really cut it, you could always put your filter down at floor level to pull what little heat leds emit down through your plants

During the winter i will 100% swap the extract and intake, so extract is at the bottom, intake at the top. i was just hoping to get away with heat matts alone instead of radiators, my wallet shudders every time i say oil rad out loud hahah

[Bobcharlieeeee]

7 minutes ago, MindSoup said:

 

If you keep your roots at 24/25 your air will rarely drop too low, my current run I've just had my temp probe in the soil set to 24 and completely ignored air temps and its been my best run yet.

Thats what i like to hear, what were you ambient temps at a guess if you dont know for certain, 

When did you start your current grow? before the coldest winter temps? 

[RUFUS HOUND]

Try to keep air temp about 27'C(measured at canopy height, over 21'C but under 30'C.  

I dont measure root temps that often, more at the start to ensure soil is above 22'C

One thing to be mindful of is the temp of the soil when you first but your pots in the tent, put them in the tent for a a day or two (before planting the seed) to allow the soil to absorb heat and the temps to equalise or use a heat mat.

I also keep my water in a 6 pint milk container in the tent, so its at room temp at watering time and doesnt shock the plants with low temp water.

I have found that the root temps usually mimic air temps within a degree or so.

like many others, I run lights on at night to counteract the low temps at winter and also have an external "rad box" to provide heat (600w oil rad in a box, drawing air from inside house to tent)

Edited March 30, 2022 by RUFUS HOUND

[RUFUS HOUND]

Ive not tried swapping the inlet to top and extraction from bottom but others have said it reduces heat requirement.

 

My led boards (2 x 85W) run at 40'C, and the ballasts at 50'C, so it might be possible to run without the rad box, if extracting from bottom but a test run or two would be needed to provide meaningful results.