First grow room set up under the stairs. Experienced growers appreciated.

I have never grown before so this will be my first set up.

I have a space under the stairs that I am going to convert and I have a few issues that need to be sorted out. There are so many suggestions and products I am just swimming in options and confusion.

Since I plan on growing year round I need to section this into two spaces with a drop partition. The space at the front near the door that is tallest 2/3 for flowering and the section at the rear 1/3 +for Veg and a drawer for starting.

The house gets cold in the winter time (sometimes below freezing at the floor in this part of the house) and so I need a barrier for the floor and will never put pots directly on the floor during that time. In the summertime we keep 68-70 degrees.

My question is - Would fully sealing the room with insulation and plastic be the best alternative or should I put up fire retardant insulation on the walls with reflective material and for the floor an insulation blanket with plastic and reflective material?

What reflective material is best?

I need light timers. Which are best?

I wish I knew an inventor because though someone is here all of the time I do not trust them to take care of the plants fully while I am away 2-4 days a week 2-4 times a month) and wish there was a timed two part water well with meter I could hook up with a timer as well as the timers for lights.

I have a handle on the lights just need to know the best light timers to purchase?

Will vent it at the top of the flower section. Will a heavy bathroom fan be enough with two oscillating fans (one in each section) be enough for 1-2 plants in each section? It is difficult to calculate but I believe the square footage is about 120.

Here is the tricky question (to me) - Since the space I have is limited is training the plant to grow up the walls and onto the ceiling (if it gets that big) an option and how tricky is that?

Any pointers or direction is appreciated.

120 sq ft.....
Do you mean cubed feet?

Example
4 x 4 - 16sq ft
4 x 4 x 6 - 96cb ft

I do. On Autopilot. No Caffeine yet.
Also... I type 120 wpm usually and this site allows me only 1-2 spaces or characters per second. Erasing is done the same way and I can press the space or any particular key, typing slowly for me, and still not get it to work. Auto-correct is on. Once something changes I am too frustrated to go back to change it. Auto save I think is the issue here for me. SOO upsetting.
3x4x10

So what are the actual dimensions of the separate areas, under your stairs?

Insulating against the cold is very important.
One frost would spell THE END
but making sure that summertime temperatures do not climb too high is also important.
You've obviously concluded that, once growing has began, you'll be unable to access and amend these areas,
without an awful lot of inconvenience.

REFLECTIVE MATERIALS
Mylar is the standard.
Usually diamond... reflective... silver....
It's surprisingly expensive.
(I bought a used 8 x 4 x 6 tent for 40% less cash
than it cost for the same area of Mylar!
and the tent has metal poles and industrial strength zips,
a tough canvas outer layer
AS WELL AS the MYLAR REFLECTIVE INTERIOR!!!
Makes absolutely NO sense!)

And there's another type of
'Ultra reflective, designed by NASA, rumoured to be the first material FDA approved for use on MARS....Yabba Yabba CASH!'
it's called ORCA REFLECTIVE SHEETING
and it costs about the same price as having your area coated with platinum!

Black and White plastic sheeting
Sometimes called PANDA sheeting (by the Yanks)
is far cheaper and only a fraction less effective.
(The original [and most expensive] grow tents - which are also considered the most effective - have white interiors.
Silver SEEMS more reflective but scientific testing proves otherwise).

Having an absolutely light proof partition between the VEG and the FLOWER areas is also essential.
18 hours of light, for VEG (some go longer, I've never seen the point) and
12 hours of light for FLOWER - Or, more importantly, 12 HOURS OF TOTAL and UNBROKEN DARKNESS.
If these 12 hours periods of absolute blackness are disturbed, if any light penetrates the darkness,
the FLOWERING is stunted and the plants can turn hermaphrodite.

Separating the areas to a light proof standard isn't difficult
separating the areas to a light proof degree but managing to ventilate BOTH AREAS with the same INLINE FAN and CARBON FILTER
may be problematic.

Thank you for the explanation. It is greatly appreciated.
I think regulating the temps in bot areas my also be difficult with just a drop curtain.
I will plan on building an insulated wall and door between and installing separate exhaust for each also.
Thank you again for your help.