Unless someone has a better idea for insulation. The roxul stuff is kind of pricey. But it's the best I can source locally afaik for acoustics.
enjoying your thread ,,,
cobs verse HPS,, after reading your thread and your investment amount, cobs will have to wait, I know plenty of people who grow with both, and HPS has a much lower set up cost, and will serve you well, there are plenty of ways to vent heat from cob led's, but then again, its more fabrication and investment of time and money,, where as a vented bulb is quick and parts fit out of the box,
both work and its not really a discussion you want to have on your thread, ( trust me on that one LOL) no really
full speed ahead with the big bulbs, plus they grow big buds!!
I would go with cheap insulation and cheap dry wall, there are paints out there that seal and repel water,, some good ones too,
Also sound is easiest of all for you to control, IMO you can hang fans on cords,, cuts tons of noise out, you can rubber mount fans, stops transition of sound thru walls and frames,
there are wonderful speed controllers for the big inline fans,, I use this one
https://www.amazon.com/PHC-Enterprise-Variac-Variable-Transformer/dp/B006NGI8VS/ref=sr_1_1/158-5956764-5721336?ie=UTF8&qid=1474643632&sr=8-1&keywords=variac+speed+controller
and you can dail in your fan speed and sound level to a stealth level for sure
you have so many options for venting and air movement,, run tests, set up thermometers, and try things after you get walls built,, testing is your friend,
buy parts from places with good return policies,, i returned som much crap when i was building my grow area, that way you can try things, if it doesnt work sent it back or take it back,, like home depot for instance sales lots of growing stuff,, espeicailly on thiere web site,, and they have a great return policy,, same thing for amazon. try things like fans,, test it, if it doesnt work for noise or size,, or speed ,, ,return it,, get a differant one
hope these ideas help some
hey are going soil or hydro?,,, I grow in Sips now