Tier 3 further reduces the layers and complexity, while providing greater future flexibility and robustness.

Tier 3 is a direct descendant of the PERSIST enclosure developed by the National Research Council Canada. Like Tier 2, it has no sheathing, but now the wood fiberboard insulation is moved entirely outboard of the framing, with a back-vented rainscreen exterior finish. Before installing the Gutex, Pro Clima INTELLO X is installed over the framing to provide a temporary WRB and long-term air and vapor control.

This is the simplest, lowest carbon (the wood frame version), most robust, and healthiest assembly.