Advice for automated c02 sealed room

[Death The Cultivator]

Looking for advice on a sealed grow room from framing to insulating etc. The room is going to be built in a garage that is not insulated.

Flowering chamber 12x4x7
Lung room 12x4x7
Veg and propagation chamber 12x4x7

I think Smart Bee might be the most affordable automated solution.

Would 25# c02 tanks be enough for each area?

Is a ventilation necessary?

Any solutions for reusing dehumidifier water?

I have no idea about framing, sealing and insulating this thing. Should I use mylar or paint the walls?

How would I go about framing and sealing doors?

Anyway to have an automatic drain valve on a flood table that turns on a pump when parameters are met?

Suggestions are appreciated