I have an unfinished basement that always has tons of beetles, spiders and cold air (yes I know most basements have this, but it is more than normal). I finally decided to take a piece of insulation out that sits on top of the foundation between the floor joists and there is a gap between the top plate and floor joists where you can see light getting into the house and a substantial amount of cold air coming in.
Is there any reason I can't fill this gap with something? Also would you guys use expandable insulating foam or something different. Blow are pictures for reference.