With the lighting height and intensity optimised I started closing up the tent and letting its air entirely depend entirely on the ducting system I had created. They then started to show signs of some struggling and even wilting. In the end I isolated the cause was to much humid air and lack of air replacement (I was trying to vent two tents via a booster fan ducting connection and a single carbon filter venting to the roof space). I could see that this air system was just not cutting it, and despite not wanting to invest more, the advantages of having each tent equipped with its own 4"carbon filer and 200m3 centrifugal fan were instantly obvious after setting it up on this tent. Ultimately I realised that setting each tent up with its own ventilation was the unavoidable choice for ongoing optimal growth and achieving the highest quality and quantity yield.
My infrared temperature gun is showing the leaf temp to be around 23c during lights on cycle. Ideally I want this up around 27-29c (apparently HIDs put out a lot of heat and infrared which like the Sun, raises the leaf temp up the range required by the plants for the photosynthesis processes to operate optimally. With cooler LED lights, other options can become a requirement in order to bring the leaf temp up to that required for optimal photosynthesis Once I have the two tents fully operational I'm hoping that will give a temp increase in the growroom that will lift the leaf temp. If it doesn't I will consider the option of venting back into the growroom to effectively create a recycling air system within the growroom and thereby the tents. If this still isn't enough eventually I may look at thermostat controlled heating in the grow room, however this would be an expensive cost so I will avoid it if at all possible via other means.
From here on out my main focus will hopefully only really need to be on providing a good wet/dry cycle with optimal strength nutrient feedings, and occasional lower leaf and sugar leaf defoliating combined with some moderate (autoflower level) LST.
Day 26 The plants suffered a dry-out of the coco. They got pretty wilty for several hours. I was not expecting the plants to have consumed so much in such a short time after there first water to run off (5 days) but this is my first time using coco with perlite, and the clay balls for drainage, so the pots feel a lot heavier when dry than my last grow, so I will be much more vigilent about feeding from now on! They're still recovering 48hours later, but they have maintained a pretty good growth rate despite the drought.
Day 26 Feeding was
Roots 1ml/l
Greendream1 2ml/l
CMX 0.3ml/l
Grostorm 2.5ml/l
Day 26 The ambient room temp has dropped enough now that I've temporarily brought in a heater to warm the tent. This is brought it up to an air temp around 28c during the light cycle. This is just the start of winter so I'll be probably changing the tent to vent back into the grow room instead of the ceiling space, and starting the second tent in the same room. This might necessitate a dehumidifier. The alternative is some sort of small heater in each tent I think. My only other grow was under a HID in summer and I spent the whole time fighting overheating. In comparison his situation is very much the opposite.
Day 27 - Little bit of leaf tip burn - Last nutrient feed was likely a bit strong. Will not increase strength at next feed. Will flush if symptoms increase.
End of week 4 summary - Tent is fully operational, circulation, ventilation, lighting are all great. Temp is going to need some work. I think I will put the extractor fan on humidity control to minimise heat lost to venting, and put in a small oil filled heater on temp control inside the tent. This avoids the need for recycling the air and subsequent dehumidification issues. I am also considering putting a 50w electric blanket under the tent. Media and pots are excellent, and nutrient levels have been good, with a slight overfeed on the last feed. Wet/Dry cycle is quicker than I expected at 5 days after first full feed, and I allowed a drought to happen. I will be much more vigilant over the media saturation from now on.