I scrapped plans of framing a room after I thought about the time I would spend building a frame, drywalling, and putting in a door... to me it was easier and more cost effective to get a tent for my rental house until I can buy my own home and put as many nails in the wall I desire...The tent is tall as hell and I did have to temporarily take down a section of furnace ducting (which happens to heat the bathroom and kitchen of the house, starting to get chilly). It is for this reason I wanted to exhaust the lights into the house. Point taken on the carbon scrubbed air, hadn't considered that-would an alternative to venting the hoods outside be to vent them to the first floor, and then exhaust the carbon scrubber outside? Or do I need to be venting at least 1500CFM outside from hoods only?
As far as layout and geographic location, our climates are probably pretty similar (MI and CO), probably a bit warmer here... night time temps (when I will have the lights going) are around 30 and continue to drop here. I am not set on intake/exhaust , I am considering placing a portable A/C outside of the tent, in the basement, and using ducting and a fan to pump cool air in from the air-conditioner (via a small lung box if I use window unit, or via ducting/dryer venting if I use portable). I have looked at window units and roll around units, unfortunately a split would be too pricey at this current moment but would consider it after harvest. Thanks for your help , I am underestimating the scope of things right now, it is a big jump for me from 1K to 4K. I learn something everyday and it is nice to have some people to ask questions of-may be asking dumb or repeat questions but sifting through ridiculous incoherent posts on this forum for hours is a head ache at times.
I wouldn't recommend bringing outside air in to cool your hoods for lots of reasons, some big ones being temperature instability, overchilling the bulbs so they don't run in their design temp. range, and condensation issues. Why not just bring it in from the unfinished basement next to the tent, down near the floor? Pull the air through your hoods and by all means, exhaust it into your house! If the hoods and ductwork are reasonably well sealed, it won't pick up much if any smell on its way through, and if it does, use the scrubber downstream of the fan and then blow it into your living space. Heat is heat, and you're paying dearly for it, so why not? Just leave someplace for air to return to the basement, preferably the coldest spot near the floor in your living space. Think of it as a cold air return.
Also, you didn't mention if you're running hydro or soil. If you're planning to do a DWC setup, you'll likely need a chiller. Built much like an AC unit, these are designed to move heat from where you want it to remain cool, to somewhere you don't mind it being warmer, using water instead of air as the working fluid. You pay for the equipment, electricity and a little extra because nothing is 100% efficient. It makes perfect sense to put this chiller unit in your living space as well, for all the same reasons it makes sense to exhaust warmed hood air into your living space. You can even use this same chiller to cool your grow space, I explain this below.
If you're drawing the air to cool your hoods from outside the tent, pulling it through the tent and then out to your living area- or for that matter anywhere else- it will not affect the pressure in the tent unless your hoods or ducting leaks pretty badly. I run 2 rows of 4 hoods all with 8" ducting, and all with just one 8" maxfan downstream of the hoods, and it's usually not even running at full speed. I see no reason why you can't cool all 4 hoods with just one fan. Run two intakes, run each one through two hoods in line with one another and connect them through a Y fitting to the fan, then out to your living space. To maximize airflow, try to keep turns and bends to a minimum.
Since what you're designing amounts to a sealed room- err, tent- you'll need CO2 augmentation of some sort. I'd strongly recommend going with tanks instead of burners in a tent.
I would recommend using a chiller system over an AC because of better efficiency (most reputable techs say about double the efficiency of AC) and the ability to better control where and how your heating and cooling activities happen. Additionally, you can cool both a hydro system and use Ice Boxes to cool your tent without trying to blow air into or out of it. If you go this route, I'd recommend a 1 ton chiller from a reputable company to cool the 4k setup you envision. I use a Chillking and I couldn't be happier with it. If you run the chiller water cold enough, the Ice Boxes will help remove water by condensation (don't try to reuse this water, just dump it) but they're no substitute for a real dehuey unit. A 70 pint Frigidaire unit runs around $200 or a little less online. CO is different from MI, but not in ways you might imagine. Both places get plenty cold in the winter, but it's almost always dry here, and almost always damp there. Therefore, you'll need dehumidification in the tent.
