Walk-out Basement Insulation Opinions

[dalola]

Wow, been off line for a few weeks, looks a lot different around here!

Hopefully some of you knowledgeable folks with construction experience are still around...

So, I've been planning a log cabin build for several years now, and I'm finally pretty well set with log supplier, builder, start date (fall '21) etc.., and looking to clarify some areas of abundant choices.

For today, I'd love to hear some opinions/experiences with basement insulation.

Here's the details of the basement in question:
Zone 5 in SE Ohio hill country, a 24x24 walk-out, 3 CMU (block) walls, 1 framed wall at the front grade.
This level will be two bedrooms, one full bath, family room, HVAC closet, and mechanical room (elec, water heater, softner, W&D, etc..)

I've researched EPS, XPS, GPS, PIR, spray, mineral wool, fiberglass, & numerous "systems" like InSoFast. Mind boggling to say the least, all the info & contradictory opinions/experiences out there!

What I think I like so far...based on simplicity (DIY), cost, effectiveness, and maximizing square footage:

In the slab, some 2" EPS on the gravel (and partially up foundation), poly cover, then the pour. Final floor will LVP.

For the CMU walls, 2.5" InSoFast, finished with pine T&G. (R10+?)

For the framed walk-out wall, 2" GPS sealed between 2x6 studs & unfaced MW, then pine T&G. (R20+?)

Interested in experiences, thoughts, flames, better products, if I'm crazy, etc... TIA!

 

[dalola]

Bump.

Traffic here sure isn't what it used to be!

 

[Rustyiron]

Your plan sounds good, but I'm not familiar with "gps". On your framed back wall/slab, are you doing a frost wall?

 

[Rustyiron]

....some may call it a stepped down footing with a stem wall to the slab

 

[dalola]

Hey Rusty, yes, that is the current plan. GPS is just EPS with infused graphite (usually referred to as Neopor), increases the R value substantially.

Thanks for responding! This new format is kinda wonky...

 

[Rustyiron]

I've been using my phone without trouble since the "new" TBN Monday, I had to move to my mac to reply just now?? No "box" for replying.
Anyway, I feel that your under slab insulation benefits highly with vertical insulation, particularly on you walk out area. If I were doing it I'd at least put foam (vertically) on the inside of your short stem wall right down to the footer and if you can stand it, up to the finished slab level. I've seen where guy's cut a 45* angle on top of the foam leaving a 1/2" for your concrete man to work to placing your slab. The 1/2'' of foam is not quite as visually objectionable. Then I'd do the outside also. Recently I did a small addition and tried this (new to me) "insulated shallow foundation" technique. It's basically a turned down monolithic slab that is very insulated (2"exp) on all sides including under the wall. It's got radiant tubing in it and performs miles above the rest of my similar construction that only has 1" of foam stood vertically on the inside only.
Now I was dealing with poured walls instead of CMU's with a void to fill, I'm unfamiliar with those results.

 

[Rustyiron]

Like this. I know it's not exactly applicable to your build, but you can see the idea.
edit; I'm not able to do this photo, might be me. search "insulated shallow foundation"

 

[dalola]

Thanks, I'll look into it!

I probably wasn't so clear in my wording, but I do plan to go vertical with the GPS on the foundation as well, so the slab is isolated, same on the walk-out.

 

[mikester]

I used the bluemax wall system 20 years ago with 3" EPS forms and 6" concrete and rebar walls. Used 4" EPS under the slab. Walls are straight, basement is dry, well insulated, quiet and tornado proof. I've been very happy with it and would do it again. If I build again I would go to the roof with the stuff.

Find a good contractor who specializes in installing these wall systems and has the right tools and forms. Go visit several of their ongoing projects at various stages. Watch them do a pour.

Run, don't walk away from anybody who won't let you see what they do and how they do it.

 

[dalola]

Yeah, I did a lot of ICF research, and I love the concept. Unfortunately, just don't have the budget for it.

In a perfect world, that's probably what I would use as well.