Best compromise between temperature and light power?

Long story short. I finally put a proper temperature/humidity sensor in my grow tent and noticed that the temps go a bit over the recommended maximum (~30C/86F) from time to time, specially towards the end of the light phase.

I have an 35 litre Aquasystem with 4 plants in a 1,2m x 1,2m x 2m grow tent with one 600W HPS and a 360m3 ventilation pulling air thru active charcoal filter on the upper portion of the tent. The tent is in a ~20m2 room with one window opened. If I open more windows or the door to the balcony the temps will drop to 15C/59F during nights and as winter is coming they would drop even more. So it's not really an option? Neither is running the lights during nights due to stealth/noise issues.

If its in a veg stage.....you could stagger your light schedule as long as the dark hrs doesnt go for more than 11 hrs.
Use your light at night instead of day

Also, increase your humidity to compensate for high temp.

Are you using an air cooled hood?

I'm at 2nd week of flowering at the moment and I don't have a cooltube. I cannot run the lights during nights due to the noise the ventilation is causing. Humidity is around 30-40% during lights on and 60-70% during nights.

I am still curious about my original question which haven't been answered. Which has the biggest negative effect. Higher temps vs. lower light output?

its hard to answer the question but if ur at ambient co2 then heat is not something you need... guys upa round 80+ are supplimenting co2... at ambient co2 u probable want to be below 80... co2 absortiption is based on temp so guys running high temps are pushing as far into disease territory as they can to acvhieve max absportion... if ur at ambient co2 that absorption maxes out around 78 degress or somehting

i get when ur running an open system it has its challenges... i think sometimes people miss that temp and humidity are relative... id grab a vpd chart offline and try to stay within that.... when i had the open system that was easier because sometimes u cant manipulate all the factors... so if ur tmeps a dropping to 60 at night... that not nesseesarily a bad thing if u can get the humidity down to 40ish... if ur temps are in the 80s its not nessearily a bad thing if u can get ur humidty to 60+ ect... so if u cant control temp, control the humidity... or if u cant control humidty, control the temp....

you said u have a tent ina room and air being pushed thru ur tent from the room and abck into the room right? you could probable close the window at night... u would probable need a dehumidifiere but plants have plenty of oxygen at night and i dont think they would expell so much co2 durring one night thast the atmosphere would become toxic for the plants or you...

in terms of yield you could look at it like this... its a two part equation.. light x co2 ... co2 absportion is based on environmental factors but like i was saying at ambient co2 the factors become much easier... u should be absorbing about the same amount of co2 thruout so id push the light to 600 if it were me....

another thing to keep in mind... in my outdoor greenhosue i have problems w temp and humidity at night sometimes late in the season... it can be 50 at night and 80 durring the day.... the plantd directly under the lights dont get powder mildew or almost any cold temp problems... then plants not under the lights are in jeopardy from time to time.... iv heard people say dont have massive swing but in my experience it has helped to bring them back up to a relativly high temp durring the days to feend off any powder mildew ect...

Thanks for the tips and information fellas.
Highly appreciated!

I did some tweaking with the ventilation and at the moment I managed to lower the max temps while having a slightly higher temps during the nights, which both seem being a move to the right direction. I will monitor the situation for a few days to see if the temps/humidity stays stable. The humidity is still higher than I would like during the nights and I will investigate if I can make the ventilation more silent with duct that has noise suppression or similar so I could run the ventilation 24/7. That should bring the humidity down during nights too. If not, I will try dehumidifier.

Okay buy the part of a portable ac that you put in the window or make someting similar. Attach venting to that and put a fan at the end hooked to a thermostat. You will have to play with the thermostat but you should be able to blow cold air into the room and lower temps.

I think the temp is fine. This stuff grows wild in afghanistan, mexico, colombia, you have to think it gets hotter than 86 degrees there lol

Get your room temps lower, if you have to open more windows, then do that. Then put your tents fan on a thermostat so it only turns on when the temps gets too high in the tent and then it will bring in cool air from the room.

NukaKola said:

Get your room temps lower, if you have to open more windows, then do that. Then put your tents fan on a thermostat so it only turns on when the temps gets too high in the tent and then it will bring in cool air from the room.

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I have one window opened 24/7. At the moment The temp is around 17C/63F during nights in the tent. I have the option to open a balcony door near the tent but that drops the nighttime temperatures to around 10C/50F and it's getting colder and colder outside, temperatures are already dropping to -2C/28F (outside) and going lower so I am a bit worried that the temps will go too cold inside the tent in the upcoming days if I keep the door open.

I can continue to keep the window open and just dial the radiators down, but in my experience that causes the nighttime humidity to go up. And as I have now managed to get the peak temperatures during lights on down to a tolerable range, the high humidity during nights is the next problem to tackle.

Again, thanks everyone for chiming in.

Update and on what you did? In similar issue.

was thinking rotating my light schedule to be on during night to combat the cold drops at night.

I think I’d have a less temp gap running lights on at night, off at day.

I have a LED though, so I hVe no noise concern

I managed to get the temps down enough by turning down the radiators in that room and leaving the window open and also running the ventilation 24/7. I managed to get it's noise down by replacing the venting with noise cancelling / dampened (dunno the correct translation, sorry) duct.

The "winter" didn't start yet and the night time temps have been around 5C outdoors so the temps are not going too low during the nights yet.

I had the same challenge and question earlier this year. I found that my plants grew well. They looked great etc but the heat seemed to have toasted some of the terps because the smell and flavors are gone of all 3 different plants that flowered in heat in the 90s. I might be wrong and I may have done a bad dry and cure, and I may have harvested early but I don't think it was either of those. It was the first time my room ever got so hot so I don't know exactly t he effect it had on my plants.