Weatherproofing Ductwork during Construction – GreenBuildingAdvisor

We’re building a “pretty good house” in SE Wisconsin, trying to do as much as we can on our own since the educational journey is part of the fun.  We’re using open web floor trusses so that hopefully all the ductwork, plumbing and electrical can be routed through them.  One of the basement walls is a walkout and that’s where we have access to insert long duct runs through the trusses.  My question is how do we weatherproof the ductwork so we can put those long runs through the trusses before the house above is closed in.  We would like to build that walkout wall soon but there will be an LVL board covering the access through the trusses at that point. The subfloor is there above but water of course still runs through the gaps in the subfloor panels.  Do we need to add the Alumaguard kind of product to make them ‘exterior’ ducts or can we just wrap them in plastic or something cheaper like that?

Thanks everyone for your help!  I’ve learned so much on GBA in the last few years!