Installing hardwood flooring in a room above a garage – GreenBuildingAdvisor

The garage has been drywalled, taped and mudded. I assume that this is still considered to be an unconditioned space, right?

I ask because I’m trying to determine what kind of underlayment I’d need in the room above the garage before I self-install 3/4″ thick, 6″ wide engineered white oak hardwood. The subfloor is plywood and the home was build in 1993.

According to the National Wood Flooring Association’s guidelines recommend a class II vapor retarder when installing over an unconditioned space.

I’m also trying to avoid asphalt-containing vapor retarders like Aquabar B, so I’ve been reading about liquid-applied vapor retarders. Are there any go-to options that the wise people of GBA can recommend?

The home was built in 1993 and is in climate zone 4A.