Tell me your secrets, coz i put a 600w hps about 2 foot away from my plants the other day and it bruned the hell out of the tops of my plants, i moved it to 3 foot and it still done it. i put them back under flors and cfl's coz theres no way i can stop the heat. ive been thinking about putting a sheet of glass over the top of the plants and see if that helps.
There's no way bro. That's impossible... you sound like your exaggerating quite a bit. I seriously doubt that you had the light 2 or 3 feet away from the tops of the plants (the canopies). There's no way your plants got burnt if you had the lights that far away, especially just a 600watt HPS.
Your sheet of glass idea, is actually a good idea buddy. This is why generally, the higher wattage (especially 1k HPS/MH lamps) usually come with a glass insert.. which in return does in fact dissipate the heat output from the bulb/ballast.. and keeps it from directly impacting the top of the plants. Kind of like a heat-sink.. kinda works on the same principles.
But anyhow, as far as your plants getting burnt from a 600watt HPS.. that was 2 or even 3 feet away from the tops of the plant(s).. I just don't see it happening. Not with a 600watt unit anyhow. You might be over feeding your plants..??? Not sure.. but I just don't see that happening.. IMO.
I've got a couple of secrets to keep the summer time indoor temps at bay.. and I live in the dirty South where it gets REALLY FUCKING hot during the summer months. I'm talking like 95`F average during the day.. with the hotter parts of the days temps reaching above 100`F with 'heat index' values topping 110`F to 115`F.. as well as high % humidity.. but yet I'm still able to keep the grow room at 82`F or lower.. even during the hottest part of the day (from 3pm to sun down) I'm able to keep my temps below 85`F and my humidity levels never get above 45%. Well, I take that back.. I think I had one day where my max RH level was like 48% or so.. but it wasn't anything drastic you know.
But yeah.. next time bro, try these tips for keeping your temps and humidity levels in check:
1.
point one ore more fans directly at your light source - (helps dissipate the heat vapors.. and keeps the air moving and gives good air circulation)
2.
use one or more fans for exhaust - ( pulling air out of the grow area/grow box/ whatever your using to grow in.. is vital to keep temps in check)
3.
use one or more fans for your 'air intake' - (pulling cooler air from outside the plants growing environment.. actually helps cool the grow area.. and then your exhaust fans will blow that air back out where it came from. Basically, you want to recycle the air.. and keep it moving. The more airflow (CFM) you have going.. the better off you'll be.)
Hopefully that helped you out some buddy. I realize sometimes things are just out of your control.. but if you'll follow those tips I gave to ya, you'll be alright and your plants will give you many thanks.. and reward you in the end (harvest time).
peace.. and have a safe but fun Memorial Day weekend everyone.