Basement Renovation - Adding Insulation - Minneapolis, MN

13 Replies

What kind of rigid insulation is required when insulation the exterior walls of a basement in St. Louis Park, MN to meet building code? 


It is common for people to use 1.5-2" closed cell foam insulation.  These come in rigid sheets and you have to tape the seams.  This acts as a good vapor barrier at the same time.  Spray foam is an option but more costly.

I assume you are pulling permits - I would just call the building official and either A) tell him your plans or B) ask what he recommends.  Many people don't like the inspectors/officials but they are good for free advice :)

If you have no insulation on the exterior, you will need to meet R-15 (continuous) on the interior side of the wall based on 2012 IECC.  This is about 3" of rigid insul.  Using polyiso is an option as well but really found at a big box store.  Stud walls would be installed after the insulation is in place.  Stagger joints when using multi layers of insul.

@John Woodrich and @Jim Adrian thanks for the advice!

The inspector who inspected my framing said I didn't have to install any insulation at all if I didn't want to however I do want to install it to help with noise and warmth. So they will just be inspecting to make sure it's the right type. I made the rookie mistake of not asking him what kind of rigid insulation to use between my studs though. 

@Josh Cook typically when you use the rigid insulation you put it against the wall and then frame your wall next to it.  Suppose you could cut it into your framing but it may be a hassle.  Don't be afraid to call him back - the last thing you want is to do a bunch of rework.

@John Woodrich I ended up calling they inspections department and they indicated R-10 rigid insulation cut to size and fit between the studs is acceptable or R-13 faced or non-faced will work! I think I’m going to go with the R-13 faced since that doesn’t require poly. Then I can staple the flaps to the studs which creates a vapor barrier and it comes pre-sized to fit the 16” OC studs. This seems like the most efficient path forward!

@Josh Cook

I know the framing's in place but in case anyone's looking for tips on insulating basement walls to create finished space and finds this thread: polyiso foam board with a reflective front and an interior vapor barrier with the reflective barrier facing out for the rim joist bays and the wall, glued in place with construction adhesive, the foam walls sealed with Tyvek tape and the bays with Great Stuff foam. Then you add a 1/2 in. air gap. Then a steel stud wall, with a foam isolation gasket under the floor track, barneyboard and PVC trim.

That's how we insulate an interior basement wall in rainsoaked Western PA with readily available materials that give us the best possible chance of not having the finished basement turn into a mold factory on us over the long haul.

@Jim K. Wow. That sounds like a great method. This is my first renovation so I have been learning as I’m going. I have also heard conflicting directions on how to insulate the basement to deal with moisture which has been confusing. Even the city gave me different options and said they would be permitted but have no recommendations for dealing with moisture.

In the end I decided go with the method I described above since it was permitted. Also on that note, my insulation inspection passed today so thanks everyone!

@Josh Cook

I know, Josh. I know. I'm not trying to be a smug know-it-all jerk to you here, and I apologize profusely if I'm coming off like one.

I wish you the very best of luck with this project.

@Jim K. My husband just added an additional room and a half in our basement and used the same specs. He explained that there are different levels in construction, this will pass inspection, this is how I would do it in my home, and what the heck was this guy thinking?

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