"Constant" day night temperatures.

As I never got a reply in https://www.rollitup.org/advanced-marijuana-cultivation/267989-uncle-bens-gardening-tweeks-pointers-200.html#post9899937 I thought I would start a new topic and see if anyone else has some tricks or suggestions.

Uncle Ben said:

Temperature and the importance of day/night differential - In general, a 85/70F (32/16C) day/night temp is best for most hybrids for maximum carbo production. What's really important is a good drop in temperature at night, of at least 15F/4C. If night temps are too high, the plant will use up the carbos manufactured during the day to the process of respiration as opposed to plant cell division/elongation (tissue production).

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My plants are not doing that bad and I don't have the luxury of a huge day/night temperature difference but would love to hear what you would do in a similar situation.

I run my lights at night (7pm to 7am).
Night time temperatures are on average 78 to 86 (with lights on).
Day time is usually around 85 to 94 (with lights off).

Small little grow for personal use only.

My lights are as follows:
1x 400watt hps
2x 105watt cfl

Extraction is a single 8" inline fan (around 800m3 an hour), pulls all the air out of the room about 4 times a minute.
I put the larger fan in to keep air moving out as fast as is possible for maximum possible c02 in the room, there is no way with my ambient temps that I can add c02 to the room as it will easily go up to 104' without constant air extration at an extremely fast rate.

If you would like to see the room:
https://www.rollitup.org/indoor-growing/754732-my-little-flowering-room.html

Tough crowd

Have you thought about a ventless heat pump?

if you go to on during the day and figure out how to keep temps in check, there should be the 10-15deg swing your looking for at the night cycle.

sound to me like the fan you have is big enough, perhaps the air that its pulling back in is being mixed with the air it's pulling out. The best way to do this is open a window or seperate where the intake comes from and where the exhaust goes.

an intake from a non-humid basement would be nice, because temps are usually 55-65 in the basement. this would let you keep the plants on at night to use extra co2 in the air also. hope this helps.


by the way a "ventless heat pump" is also known as a mini split a/c unit

Nizza said:

if you go to on during the day and figure out how to keep temps in check, there should be the 10-15deg swing your looking for at the night cycle.

sound to me like the fan you have is big enough, perhaps the air that its pulling back in is being mixed with the air it's pulling out. The best way to do this is open a window or seperate where the intake comes from and where the exhaust goes.

an intake from a non-humid basement would be nice, because temps are usually 55-65 in the basement. this would let you keep the plants on at night to use extra co2 in the air also. hope this helps.


by the way a "ventless heat pump" is also known as a mini split a/c unit

Click to expand...

The problem is that our night time ambient temperatures in summer hit around 24'c to 26'c (75'f to 79'f) and day time is around 30'c to 38'c (86'f to 100'f).

My wife would murder me in my sleep if I got my flowering room an aircon instead of the bedrooms Also, I do not have the cash for an air-con right now and if I did it would also need a high pressure switch due to air vents sucking the cool air out the whole time and need to be at the very least an 18000 BTU unit (I have a friend that does this for a living, he came and did my calculations for me based on me only moving around 200f3h or air out the room).

My intake and my vent are both outdoors. there is nothing I can do about this.
The intake never ever gets direct sunlight.

I was thinking of using an earth pipe to cool the room but the intake is visible from outside of the property and I do not want any visible changes to be made.

I also can not easily cut a different vent hole.
I would have to go through a 4 brick thick wall with a 1/4" sheet of steel in the middle of the bricks (my flowering is inside a walk in safe).