How do I finish basement walls?

I haven't seen the system in person, but I see a few issues.

* the strength of the pieced- together polyethylene extrusions that are supposed to carry the drywall.

On a plumb block wall, the extrusions will work out. But on a typical poured foundation, this would be a difficult job.

Securing the two foot panels to the wall in compliance with Codes, and especially on a typical poured foundation will require lots more labour than with other methods. Each panel will have to be mechanically adhered. On the other hand, multiple 2x8 /2x10 or even 4x8 panels of traditional XPS can be attached with a fraction of the fasteners using strapping.

* the insulation value. This is expanded polystyrene, (EPS) not extruded polystyrene (XPS). EPS is ususally R4 per inch, yet ISF claims an R value of 10.44 over a poured 8" wall and R 11.08 over a 12" block wall. The manufacturer doesn't explain how the R value of the panels increases based on the substrate. There are also seams every two feet horizontally as well as the typical vertical seams. These are not shiplapped and should be taped.

You don't mention where you are located. But even the claimed R11.08 is well below recommended levels in most of the US and Canada. To reach those levels, you will have to put up a stud wall to the interior of the ISF panels.

Probably can be done cheaper and with better R value and pass codes.

https://www.greenbuildingadvisor.com/article/how-to-insulate-a-basement-wall

https://www.homeconstructionimprovement.com/how-to-insulate-basement-walls/

http://www.ifinishedmybasement.com/basement-waterproofing/rigid-foam-insulation/

You must realize a basement is usually above 45°F year round but can become beneath 45°F without the pipes freezing.

As that is exterior climates, Exterior Paint is very durable more than interior paint.

In addition is the fact basements have small lower windows that rarely get direct sunlight or moonlight, and thus your basement needs more light reflective surfaces.

Especially when you want a Specific Color mix, or Variety of Colors to Designate Areas or improve Lighting Efficiency, the Custom Paints are Effective and Energy efficient too by using Bright Colors where Light is needed Most rather than a 100W Equivalent where a 75W equivalent may do.

For example:

Wash Room Area: White

Workspace and Workbench Area: Light Gray or Tan

Decorations and Decor Storage: Cocoa Brown

Entry to the Basement Stairs: Dusty Gray

Exit: Dusty Gray with White or Yellow Edging

Clothing Storage: Dusty Blue or Blue Gray

Boiler Room or Coal Bin: Brick Red or Maroon

Window Borders, Pantry and Freezer: Tan or White

Unless you are going for a Bland Primer look, The extra cost for a Variety of Custom Paints is Near to the cost for Less Variety but worth the additional expense.

Why go with Less Variety and dark primers? To save $6 short term that you pay $350 extra for, in Long Term Lighting?

Here is one way to finish your walls. https://www.youtube.com/watch?v=QZqhzFbxYKk" rel="nofollow noopener" target="_blank">..https://www.youtube.com/watch?v=QZqhzFbxYKk