Greenhouse Heating using Lights Update

[Vlad Jovanovic]

Ok, so basically what I’ve found is that using the set-up described in the previous blog, is that I was able to obtain a 9-12 degC difference in air temps, in a 2.4 m3 space using just the heat off of the T-8’s, which were left running 24/7. This increased to 20+ degC when the 250MH kicked in (from 12 midnight till 7:30am). I was able to sprout over 100 plants split between 3 different cultivars. COS Romaine, Spinach, and a local variety of red/green lettuce. After sprouting, which took place inside of three or four days for the lettuces and 7-9 days for the spinach, things chugged along slowly which to be expected.

15 days ago I took 4 of each cultivar and put them in much more hospitable conditions under a PL-L rig I’m trying out. (I hope that PL-L will be a viable, cheaper, more lumen/Watt alternative to HighOutput T-5’s and have no idea why these lights seem to be so little known)?

There was definitely a correlation to temps achieved with lights, and ambient air temps. For instance as it got further below zero, say -7, the lighting had a harder time keeping temps up (my target temp was 16-17 degrees which I tried to upkeep by ventilating either more or less)...

This may come in handy for anyone say, trying to do something in a cold garage which would necessitate the use of some kind of lighting. HID or otherwise. I would suggest creating a grow space with bubblewrap packaging (don't hermetically seal the space off though) material and playing around a bit with the heat. Use a small AC fan was used to push around the air, and if you're like me your probably aiding in air exchanged by not-stop entering and exiting the space to check on things and take notes :) So you probably don't need extraction fans etc...

For comparison here is a pic of those same 12 plants today, after 15 days ‘in paradise’… 

Here on the other hand (no pun intended) is a sprout planted on the same day left in the much cooler space...The differences although expected, are still striking to see firsthand...