basement wall insulation

[stustustudio]

Working on a commercial building, climate zone 4 (not marine) with poured concrete basement walls and steel frame/metal studs above. We have typically detailed insulation for a basement to be on the interior face of a poured wall, but I'm thinking it would be better to run the R 7.5 ci on the exterior face. It would keep the insulation truly "continuous" with that on the outside of the metal studs and would not eat up usable interior SF. It seems like this is allowable and would only need to extend down 10' per IECC C402.2.4 on below grade walls. However, many details I've referenced online show basement insulation on the interior side of the wall. Covering the insulation is the biggest concern I see at the moment. It looks like there are some prefinished insulating products out there - has anyone had good experience with this? Are there other downsides I'm missing?

Thanks!

 

[Mr. Inspector]

Need to know what year of what code you need to use. The energy code changes a lot with every issue.

 

[stustustudio]

IECC 2018 is adopted code for this project. Thanks!

 

[Genduct]

Working on a commercial building, climate zone 4 (not marine) with poured concrete basement walls and steel frame/metal studs above. We have typically detailed insulation for a basement to be on the interior face of a poured wall, but I'm thinking it would be better to run the R 7.5 ci on the exterior face. It would keep the insulation truly "continuous" with that on the outside of the metal studs and would not eat up usable interior SF. It seems like this is allowable and would only need to extend down 10' per IECC C402.2.4 on below grade walls. However, many details I've referenced online show basement insulation on the interior side of the wall. Covering the insulation is the biggest concern I see at the moment. It looks like there are some prefinished insulating products out there - has anyone had good experience with this? Are there other downsides I'm missing?

Thanks!

Seems that having the insulation on the exterior will allow that Porous Concrete to be warmer than if the Insulation were installed on the interior thereby reducing the thermal bridge AND reducing the opportunity for the extra moisture that is usually in basements from condensing. Of course that porous concrete has a perm that will allow some liquid water to move because of capillary action.

Since this is Bldg science, I am sure that there will be a wide range of opinions in this application

 

[Paul Sweet]

My main concern with exterior insulation is if you're in a heavy termite infestation zone.

Insulation outside the waterproofing membrane will serve as protection for the membrane as well as thermal insulation. It would be best to take the insulation down to the footing.

I guess interior insulation is more commonly shown is because it is cheaper and requires less coordination.