basement sill plate insulation replacement?

Question

I’m trying to redo basement insulation, but not sure if what I’m seeing from the original owner was correct to begin with, or up to current standards.

Most research I’ve seen talks about rim joist insulation, but doesn’t cover what to do for a longer run like this on top of a sill plate.

I have two walls like this that are the front and back of my basement/ home. As the picture shows, batt insulation may be preferred so that I can insert it around the multiple wires seen in the photo. I’m not sure that I could make the intricate cuts Necessary for these wire notches into foam board.

That being said, I’m not sure if batt insulation is the best overall approach, given moisture concerns.

If I went with batt insulation, given the narrow width of the sill plate, I assume I may need to cut the insulation lengthwise so that the insulation doesn’t hang off of the sill plate?

Would really appreciate any recommendations!

Answer 1

You are not insulating the sill plate here. You're insulating the rim joist, which is the actual component against the outside world. If you had energy walls inside your concrete foundation, then you would worry about insulating the sill plate and lapping onto those energy walls.

This is commonly done with fiberglass batts, which you would press against the rim joist up tight to the subfloor, and then bend down across the sill plate. You could trim it just to fit the rim joist, but eventually there may be some value in insulating the sill plate as well.