Covered porch floor options – GreenBuildingAdvisor

We’re adding an addition to our home (Chicago, climate zone 5), and one corner of the first floor has a 6’x6′ covered porch, with basement underneath it and primary bedroom closet around it, and having a hard time deciding which way to go for the floor system. The porch currently has some advantech on floor, but it’s been a temporary work surface and has some slope issues, so need to do something new. I want to maintain air sealing and protection from elements on floor of porch, and tie into the zip board on the walls of the porch and knee wall underneath it. The plan is for whatever I use as flooring to be covered with some epdm membrane I have left over from a commercial project, lapped up the walls and down over the sides, before the exterior insulation goes on, and then put in decking on sleepers with epdm on bottom of sleepers over it. So here’s the question – do I use 5/8″ zip that I can tie into the rest of the zip and will basically have redundant protection with the epdm, or 3/4″ advantech with the epdm over it? Whatever I used will be pitched away from house at 1/4″, and double r-30 rockwool insulation in floor underneath assembly. Note – not enough room between door threshold and porch floor to use polyiso under epdm.