Zip Board
My dad recommended this for the walls early in the build. Basically it includes the house wrap with the sheathing so you don't need to wrap the house in Tyvek. Turns out, many people are going this route for tiny houses.
Pricing out plywood + Tyvek compared to the Zip System, they were very close in cost. We estimated that we will use 20, 7/16"- 4x8 sheets.
About:
ZIP System® sheathing and tape is an innovative structural roof and wall system with an integrated water resistant and air barrier that streamlines the weatherization process and transforms it with a simple two-step installation. Just put up the panels and tape the seams. ZIP System™ tape is so easy it turns taping into a one-man job; and so fast, it installs 40% quicker than housewrap.