Need advice on putting cedar T&G planks on ceiling in bathroom
I'm redoing the bathroom and need some advice on how to properly put up Western Red cedar planks on the ceiling. Above the ceiling is the attic (only insulation, no floorboards). I live in Northern Virginia (Climate Zone 4, mixed humid).
This is what I've gleaned so far from research:
1) Varnish all sides except living area side of cedar planks
2) Nail 1/8" to 1/2" battens to joists (16" o.c.)
3) Affix cedar to battens using flooring method (nail 45 degree into tongue)
4) Use some sort of oil (Danish oil seems to be recommended by the Western Red Cedar Lumber Association) to finish facing side of cedar, and keep it looking colorful
Does this sound correct? How effectively would any moisture that gets past the cedar vent through 20" of insulation? Could I just install 1/2" plywood boards on ceiling, drill x number of 1/2" holes for venting and save myself the hassle of battens?