No, they are right... This is kinda on the same level (kinda!) as setting the seedling on your window sill.... the life support structure they need, is simply not there, they will grow into death.
As someone who's gone both routes, building and buying grow space.... I personally recommend buying when possible. (or a combo) But a 4x4 or even a 6x4 to 6x6 tent. Build a smaller area 2x4 inside there for your veg area. (I set my buddy up w/ a 6x6x6.5 tent, and a 2x2x4 inside that, w/ T5's for the veg room. 600w HPS in the main area for flowering.
Whole lotta fans..... filter/carbon etc. if actual stealth is your goal, if you just dont want 20hrs of light shining at you, tents should be find w/o them, but i suggest venting tent heat outside. This keeps smell down, home temps down, and helps maintain a fresh air flow into the tent, keeping fresh CO2 for your babies.
(If its all CFL/LED low heat stuff... just get a CO2 regulator n a tank, keep that bitch sealed up)
The tin foil thing your getting chewed for..... Aluminum foil reflects both light and heat, and gets those pesky wrinkles n crinkles so easy.... can easily cause hot spots to be reflected onto, and burn your plants. Cooks them... cuz aluminum foil, is for cooking. Mylar reflects over 90% of light that hits it, but only a tiny fraction of the heat.
For the size......reflector.... youre building.... go get one of the shiny birthday balloons from the local shop, razor blade the very edges... cut a hole in the center big enough for a lightbulb socket... poof, its a reflector, lol.
Using CFL's... if the bulb looks like youd put it into any lamp in your home without cocking your head to the side and lifting an eyebrow.... its too small. Go 150w equiv. or better, none of that 13/27 watt silliness. More power, your playing God here, you need to make the sun, not the moon.
Lose the cockeyed lamps as soon as the budget allows, get something cheap n simple til you go HID. Like a clamp reflector for pet lights. (eliminates need for reflector, so u can use mylar to line walls.
As for what you actually asked for..... IF you determined to stick with it, just outta pride, and to see what it can do.... (I'd understand that, its a guy thing...) Assuming you are opening this thing at least 1-2x a day to vent out the humidity, and check/change.... Why not drop 2-3 bottles of water in the freezer.... stick a frozen one in the room each morning, and each bedtime.... Obviously this is gonna add a bit of humidity, youll want the bottle standing in a small bowl for condensate to drip to, and a fan blowing across it, breathing cool air into the bulbs/plants.
The more airflow on the plants, the better. I gave 6" fans aimed at my 125w CFLs (NOT 125w equiv's...) and they stay downright cool to the touch now. I actually forgot about a plant last week, its got a tiny burn on a leaf.... I had to pull the branch out of the bulb, n thats all the damage it took.
Case fans/USB fans are great if you are space limited. more fans, lots more fans
Its always good... too hot? more fans. Too humid? More fans! Stankin the place up? Big ass fan, point it out the roof with a filter on the starting end!