Fill gaps between board sheathing?

96 yr old house (Seattle 4c) with cedar shakes nailed to boards nailed to studs. I’m replacing a couple 4’ x 4’ sections due to an internal water leak. I’m… 96 yr old house (Seattle 4c) with cedar shakes nailed to boards nailed to studs. I’m replacing a couple 4’ x 4’ sections due to an internal water leak. I’m…Read MoreGreenBuildingAdvisor