If air exhaust is kept at equal rates, a more effecient light source will create less ambient temp rise than a less effecient light source.
Heat flows from hot to cold, this is important because when you use the entire surface area of the tent to dissipate the light portion of the fixture energy, the temp of the tent walls is small (and also has a 70% greater cp), so it has less of a gradient to flow enegy across before its equalized, which means it flows at a slow rate. When half of the fixtures enegy is kept in a small form factor like a light bulb or ballast, then the gradient is much greater at the fixture-air boundary, and the enegy flows from the hot fixture to the air much faster. On top of this, the tent walls will absorb 5x as much light energy as the air can absorb the hot portion of the fixture, and in a low effecient fixture the hot portion is the greatest % of the enegy output. This means the air increases temp much faster from the hot portion of the light compared to the air temp increase of an equivalent amount of energy that's transferred to the tent walls, plants, pots, water, ect, and then onto the air. The fixture doesn't have a huge surface area connected to the outside air or floor, and has to dissipate a greater % of energy than the tent walls do for a low effecient fixture. Also, the hot portion of the fixture can't dissipate energy to the outside air like the tent walls can, the hot portion of the fixture can only dissipate enegy to the inside of the tent.
A hot fixture is your enemy when talking about ambient temp rise. You have to isolate the air that the hot portion comes into contact with, ie a cool tube, and/or increase exhaust rates to notice the same ambient temp rise as a high effecient fixture. There's a thread on here where someone goes through and explains it with graphs ect, but if you don't understand thermodynamics or at least the basis, you probably will end up disagreeing.
In the most extreme cases it's maybe an effeciency delta of 20%, so while there is a huge difference when comparing the total ambient air temp increase due to the % energy being transferred to the tent air vs the total ambient air temp increase due to the % energy being transferred to the tent wall (considering equal energies applied), both those types of fixtures will still produce a hot portion, so altogether it makes a noticeable difference but theres no free lunch, you'll still have to vent QBs under most circumstances..
One day ppl will start to see I'm not just talking out my ass lol.. One day..
